2017
Frey, V M; Mavadia, S; Norris, L M; Ferranti, W; Lucarelli, D; Viola, L; Biercuk, M J
Application of optimal band-limited control protocols to quantum noise sensing Journal Article
In: Nature Communications, vol. 8, no. 1, pp. 2189, 2017.
@article{Frey.2017,
title = {Application of optimal band-limited control protocols to quantum noise sensing},
author = {V M Frey and S Mavadia and L M Norris and W Ferranti and D Lucarelli and L Viola and M J Biercuk},
url = {https://www.nature.com/articles/s41467-017-02298-2},
doi = {10.1038/s41467-017-02298-2},
year = {2017},
date = {2017-01-01},
journal = {Nature Communications},
volume = {8},
number = {1},
pages = {2189},
abstract = {Essential to the functionality of qubit-based sensors are control protocols, which shape their response in frequency space. However, in common control routines out-of-band spectral leakage complicates interpretation of the sensor’s signal. In this work, we leverage discrete prolate spheroidal sequences (a.k.a. Slepian sequences) to synthesize provably optimal narrowband controls ideally suited to spectral estimation of a qubit’s noisy environment. Experiments with trapped ions demonstrate how spectral leakage may be reduced by orders of magnitude over conventional controls when a near resonant driving field is modulated by Slepians, and how the desired narrowband sensitivity may be tuned using concepts from RF engineering. We demonstrate that classical multitaper techniques for spectral analysis can be ported to the quantum domain and combined with Bayesian estimation tools to experimentally reconstruct complex noise spectra. We then deploy these techniques to identify previously immeasurable frequency-resolved amplitude noise in our qubit’s microwave synthesis chain. Control of qubits’ frequency response by dynamical decoupling is usually vexed by control’s out-of-band harmonics, a problem known in metrology as “spectral leakage”. Here, the authors reduce this problem by orders of magnitude exploiting discrete prolate spheroidal sequences to control a trapped-ion qubit.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Essential to the functionality of qubit-based sensors are control protocols, which shape their response in frequency space. However, in common control routines out-of-band spectral leakage complicates interpretation of the sensor’s signal. In this work, we leverage discrete prolate spheroidal sequences (a.k.a. Slepian sequences) to synthesize provably optimal narrowband controls ideally suited to spectral estimation of a qubit’s noisy environment. Experiments with trapped ions demonstrate how spectral leakage may be reduced by orders of magnitude over conventional controls when a near resonant driving field is modulated by Slepians, and how the desired narrowband sensitivity may be tuned using concepts from RF engineering. We demonstrate that classical multitaper techniques for spectral analysis can be ported to the quantum domain and combined with Bayesian estimation tools to experimentally reconstruct complex noise spectra. We then deploy these techniques to identify previously immeasurable frequency-resolved amplitude noise in our qubit’s microwave synthesis chain. Control of qubits’ frequency response by dynamical decoupling is usually vexed by control’s out-of-band harmonics, a problem known in metrology as “spectral leakage”. Here, the authors reduce this problem by orders of magnitude exploiting discrete prolate spheroidal sequences to control a trapped-ion qubit.
Bermudez, A; Xu, X; Nigmatullin, R; O’Gorman, J; Negnevitsky, V; Schindler, P; Monz, T; Poschinger, U G; Hempel, C; Home, J; Schmidt-Kaler, F; Biercuk, M; Blatt, R; Benjamin, S; Müller, M
Assessing the Progress of Trapped-Ion Processors Towards Fault-Tolerant Quantum Computation Journal Article
In: Physical Review X, vol. 7, no. 4, pp. 041061, 2017.
@article{Bermudez.20174vd,
title = {Assessing the Progress of Trapped-Ion Processors Towards Fault-Tolerant Quantum Computation},
author = {A Bermudez and X Xu and R Nigmatullin and J O’Gorman and V Negnevitsky and P Schindler and T Monz and U G Poschinger and C Hempel and J Home and F Schmidt-Kaler and M Biercuk and R Blatt and S Benjamin and M Müller},
url = {https://journals.aps.org/prx/abstract/10.1103/PhysRevX.7.041061},
doi = {10.1103/physrevx.7.041061},
year = {2017},
date = {2017-01-01},
journal = {Physical Review X},
volume = {7},
number = {4},
pages = {041061},
abstract = {A quantitative assessment of the progress of small prototype quantum processors towards fault-tolerant quantum computation is a problem of current interest in experimental and theoretical quantum information science. We introduce a necessary and fair criterion for quantum error correction (QEC), which must be achieved in the development of these quantum processors before their sizes are sufficiently big to consider the well-known QEC threshold. We apply this criterion to benchmark the ongoing effort in implementing QEC with topological color codes using trapped-ion quantum processors and, more importantly, to guide the future hardware developments that will be required in order to demonstrate beneficial QEC with small topological quantum codes. In doing so, we present a thorough description of a realistic trapped-ion toolbox for QEC and a physically motivated error model that goes beyond standard simplifications in the QEC literature. We focus on laser-based quantum gates realized in two-species trapped-ion crystals in high-optical aperture segmented traps. Our large-scale numerical analysis shows that, with the foreseen technological improvements described here, this platform is a very promising candidate for fault-tolerant quantum computation.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
A quantitative assessment of the progress of small prototype quantum processors towards fault-tolerant quantum computation is a problem of current interest in experimental and theoretical quantum information science. We introduce a necessary and fair criterion for quantum error correction (QEC), which must be achieved in the development of these quantum processors before their sizes are sufficiently big to consider the well-known QEC threshold. We apply this criterion to benchmark the ongoing effort in implementing QEC with topological color codes using trapped-ion quantum processors and, more importantly, to guide the future hardware developments that will be required in order to demonstrate beneficial QEC with small topological quantum codes. In doing so, we present a thorough description of a realistic trapped-ion toolbox for QEC and a physically motivated error model that goes beyond standard simplifications in the QEC literature. We focus on laser-based quantum gates realized in two-species trapped-ion crystals in high-optical aperture segmented traps. Our large-scale numerical analysis shows that, with the foreseen technological improvements described here, this platform is a very promising candidate for fault-tolerant quantum computation.
Mavadia, Sandeep; Frey, Virginia; Sastrawan, Jarrah; Dona, Stephen; Biercuk, Michael J
Prediction and real-time compensation of qubit decoherence via machine learning Journal Article
In: Nature Communications, vol. 8, no. 1, pp. 14106, 2017.
@article{Mavadia.2017,
title = {Prediction and real-time compensation of qubit decoherence via machine learning},
author = {Sandeep Mavadia and Virginia Frey and Jarrah Sastrawan and Stephen Dona and Michael J Biercuk},
doi = {10.1038/ncomms14106},
year = {2017},
date = {2017-01-01},
journal = {Nature Communications},
volume = {8},
number = {1},
pages = {14106},
abstract = {The wide-ranging adoption of quantum technologies requires practical, high-performance advances in our ability to maintain quantum coherence while facing the challenge of state collapse under measurement. Here we use techniques from control theory and machine learning to predict the future evolution of a qubit’s state; we deploy this information to suppress stochastic, semiclassical decoherence, even when access to measurements is limited. First, we implement a time-division multiplexed approach, interleaving measurement periods with periods of unsupervised but stabilised operation during which qubits are available, for example, in quantum information experiments. Second, we employ predictive feedback during sequential but time delayed measurements to reduce the Dick effect as encountered in passive frequency standards. Both experiments demonstrate significant improvements in qubit-phase stability over ‘traditional’ measurement-based feedback approaches by exploiting time domain correlations in the noise processes. This technique requires no additional hardware and is applicable to all two-level quantum systems where projective measurements are possible. Control engineering techniques are promising for realizing stable quantum systems to counter their extreme fragility. Here the authors use techniques from machine learning to enable real-time feedback suppression of decoherence in a trapped ion qubit by predicting its future stochastic evolution.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The wide-ranging adoption of quantum technologies requires practical, high-performance advances in our ability to maintain quantum coherence while facing the challenge of state collapse under measurement. Here we use techniques from control theory and machine learning to predict the future evolution of a qubit’s state; we deploy this information to suppress stochastic, semiclassical decoherence, even when access to measurements is limited. First, we implement a time-division multiplexed approach, interleaving measurement periods with periods of unsupervised but stabilised operation during which qubits are available, for example, in quantum information experiments. Second, we employ predictive feedback during sequential but time delayed measurements to reduce the Dick effect as encountered in passive frequency standards. Both experiments demonstrate significant improvements in qubit-phase stability over ‘traditional’ measurement-based feedback approaches by exploiting time domain correlations in the noise processes. This technique requires no additional hardware and is applicable to all two-level quantum systems where projective measurements are possible. Control engineering techniques are promising for realizing stable quantum systems to counter their extreme fragility. Here the authors use techniques from machine learning to enable real-time feedback suppression of decoherence in a trapped ion qubit by predicting its future stochastic evolution.
Marciniak, Christian D; Ball, Harrison B; Hung, Alex T -H; Biercuk, Michael J
Towards fully commercial, UV-compatible fiber patch cords Journal Article
In: Optics Express, vol. 25, no. 14, pp. 15643, 2017.
@article{Marciniak.2017,
title = {Towards fully commercial, UV-compatible fiber patch cords},
author = {Christian D Marciniak and Harrison B Ball and Alex T -H Hung and Michael J Biercuk},
doi = {10.1364/oe.25.015643},
year = {2017},
date = {2017-01-01},
journal = {Optics Express},
volume = {25},
number = {14},
pages = {15643},
abstract = {We present and analyze two pathways to produce commercial optical-fiber patch cords with stable long-term transmission in the ultraviolet (UV) at powers up to textbackslashtextasciitilde 200 mW, and typical bulk transmission between 66-75 %. Commercial fiber patch cords in the UV are of great interest across a wide variety of scientific applications ranging from biology to metrology, and the lack of availability has yet to be suitably addressed. We provide a guide to producing such solarization-resistant, hydrogen-passivated, polarization-maintaining, connectorized and jacketed optical fibers compatible with demanding scientific and industrial applications. Our presentation describes the fabrication and hydrogen loading procedure in detail and presents a high-pressure vessel design, calculations of required H2 loading times, and information on patch cord handling and the mitigation of bending sensitivities. Transmission at 313 nm is measured over many months for cumulative energy on the fiber output of > 10 kJ with no demonstrable degradation due to UV solarization, in contrast to standard uncured fibers. Polarization sensitivity and stability are characterized yielding polarization extinction ratios between 15 dB and 25 dB at 313 nm, where we find patch cords become linearly polarizing. We observe that particle deposition at the fiber facet induced by high-intensity UV exposure can (reversibly) deteriorate patch cord performance and describe a technique for nitrogen purging of fiber collimators which mitigates this phenomenon.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We present and analyze two pathways to produce commercial optical-fiber patch cords with stable long-term transmission in the ultraviolet (UV) at powers up to textbackslashtextasciitilde 200 mW, and typical bulk transmission between 66-75 %. Commercial fiber patch cords in the UV are of great interest across a wide variety of scientific applications ranging from biology to metrology, and the lack of availability has yet to be suitably addressed. We provide a guide to producing such solarization-resistant, hydrogen-passivated, polarization-maintaining, connectorized and jacketed optical fibers compatible with demanding scientific and industrial applications. Our presentation describes the fabrication and hydrogen loading procedure in detail and presents a high-pressure vessel design, calculations of required H2 loading times, and information on patch cord handling and the mitigation of bending sensitivities. Transmission at 313 nm is measured over many months for cumulative energy on the fiber output of > 10 kJ with no demonstrable degradation due to UV solarization, in contrast to standard uncured fibers. Polarization sensitivity and stability are characterized yielding polarization extinction ratios between 15 dB and 25 dB at 313 nm, where we find patch cords become linearly polarizing. We observe that particle deposition at the fiber facet induced by high-intensity UV exposure can (reversibly) deteriorate patch cord performance and describe a technique for nitrogen purging of fiber collimators which mitigates this phenomenon.
Robertson, Alan; Granade, Christopher; Bartlett, Stephen D; Flammia, Steven T
Tailored Codes for Small Quantum Memories Journal Article
In: Physical Review Applied, vol. 8, no. 6, pp. 064004 EP –, 2017.
@article{Robertson.2017,
title = {Tailored Codes for Small Quantum Memories},
author = {Alan Robertson and Christopher Granade and Stephen D Bartlett and Steven T Flammia},
year = {2017},
date = {2017-01-01},
journal = {Physical Review Applied},
volume = {8},
number = {6},
pages = {064004 EP –},
abstract = {We demonstrate that small quantum memories, realized via quantum error correction in multi-qubit devices, can benefit substantially by choosing a quantum code that is tailored to the relevant error model of the system. For a biased noise model, with independent bit and phase flips occurring at different rates, we show that a single code greatly outperforms the well-studied Steane code across the full range of parameters of the noise model, including for unbiased noise. In fact, this tailored code performs almost optimally when compared with 10,000 randomly selected stabilizer codes of comparable experimental complexity. Tailored codes can even outperform the Steane code with realistic experimental noise, and without any increase in the experimental complexity, as we demonstrate by comparison in the observed error model in a recent 7-qubit trapped ion experiment.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We demonstrate that small quantum memories, realized via quantum error correction in multi-qubit devices, can benefit substantially by choosing a quantum code that is tailored to the relevant error model of the system. For a biased noise model, with independent bit and phase flips occurring at different rates, we show that a single code greatly outperforms the well-studied Steane code across the full range of parameters of the noise model, including for unbiased noise. In fact, this tailored code performs almost optimally when compared with 10,000 randomly selected stabilizer codes of comparable experimental complexity. Tailored codes can even outperform the Steane code with realistic experimental noise, and without any increase in the experimental complexity, as we demonstrate by comparison in the observed error model in a recent 7-qubit trapped ion experiment.
Rej, Ewa; Gaebel, Torsten; Waddington, David EJ; Reilly, David J
Hyperpolarized nanodiamond surfaces Journal Article
In: Journal of the American Chemical Society, vol. 139, no. 1, pp. 193–199, 2017.
@article{rej2017hyperpolarized,
title = {Hyperpolarized nanodiamond surfaces},
author = {Ewa Rej and Torsten Gaebel and David EJ Waddington and David J Reilly},
year = {2017},
date = {2017-01-01},
journal = {Journal of the American Chemical Society},
volume = {139},
number = {1},
pages = {193–199},
publisher = {ACS Publications},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Mahoney, Alice C; Colless, James I; Peeters, Lucas; Pauka, Sebastian J; Fox, Eli J; Kou, Xufeng; Pan, Lei; Wang, Kang L; Goldhaber-Gordon, David; Reilly, David J
Zero-field edge plasmons in a magnetic topological insulator Journal Article
In: Nature communications, vol. 8, no. 1, pp. 1836, 2017.
@article{mahoney2017zero,
title = {Zero-field edge plasmons in a magnetic topological insulator},
author = {Alice C Mahoney and James I Colless and Lucas Peeters and Sebastian J Pauka and Eli J Fox and Xufeng Kou and Lei Pan and Kang L Wang and David Goldhaber-Gordon and David J Reilly},
year = {2017},
date = {2017-01-01},
journal = {Nature communications},
volume = {8},
number = {1},
pages = {1836},
publisher = {Nature Publishing Group UK London},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Waddington, David EJ; Sarracanie, Mathieu; Zhang, Huiliang; Salameh, Najat; Glenn, David R; Rej, Ewa; Gaebel, Torsten; Boele, Thomas; Walsworth, Ronald L; Reilly, David J; others,
Nanodiamond-enhanced MRI via in situ hyperpolarization Journal Article
In: Nature communications, vol. 8, no. 1, pp. 15118, 2017.
@article{waddington2017nanodiamond,
title = {Nanodiamond-enhanced MRI via in situ hyperpolarization},
author = {David EJ Waddington and Mathieu Sarracanie and Huiliang Zhang and Najat Salameh and David R Glenn and Ewa Rej and Torsten Gaebel and Thomas Boele and Ronald L Walsworth and David J Reilly and others},
year = {2017},
date = {2017-01-01},
journal = {Nature communications},
volume = {8},
number = {1},
pages = {15118},
publisher = {Nature Publishing Group UK London},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Waddington, David EJ; Boele, Thomas; Rej, Ewa; McCamey, Dane R; Gaebel, Torsten; Reilly, David J
Nanodiamond imaging with hyperpolarized 13C MRI Journal Article
In: Inter. Soc. Mag. Res. Med., 2017.
@article{waddington2017nanodiamondb,
title = {Nanodiamond imaging with hyperpolarized 13C MRI},
author = {David EJ Waddington and Thomas Boele and Ewa Rej and Dane R McCamey and Torsten Gaebel and David J Reilly},
year = {2017},
date = {2017-01-01},
journal = {Inter. Soc. Mag. Res. Med.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Mahoney, AC; Colless, JI; Pauka, SJ; Hornibrook, JM; Watson, JD; Gardner, GC; Manfra, MJ; Doherty, AC; Reilly, DJ
On-chip microwave quantum hall circulator Journal Article
In: Physical Review X, vol. 7, no. 1, pp. 011007, 2017.
@article{mahoney2017chip,
title = {On-chip microwave quantum hall circulator},
author = {AC Mahoney and JI Colless and SJ Pauka and JM Hornibrook and JD Watson and GC Gardner and MJ Manfra and AC Doherty and DJ Reilly},
year = {2017},
date = {2017-01-01},
journal = {Physical Review X},
volume = {7},
number = {1},
pages = {011007},
publisher = {APS},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Boele, Thomas; Gaebel, Torsten; Reilly, David; Rej, Ewa; Waddington, David; Glenn, David; Rosen, Matthew; Salameh, Najat; Sarracanie, Mathieu; Walsworth, Ronald; others,
Nanodiamond-enhanced MRI via in situ hyperpolarization Journal Article
In: 2017.
@article{boele2017nanodiamond,
title = {Nanodiamond-enhanced MRI via in situ hyperpolarization},
author = {Thomas Boele and Torsten Gaebel and David Reilly and Ewa Rej and David Waddington and David Glenn and Matthew Rosen and Najat Salameh and Mathieu Sarracanie and Ronald Walsworth and others},
year = {2017},
date = {2017-01-01},
publisher = {Nature Publishing Group},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Gaebel, Torsten; Reilly, David; Rej, Ewa; Waddington, David
Hyperpolarized nanodiamond surfaces Journal Article
In: 2017.
@article{gaebel2017hyperpolarized,
title = {Hyperpolarized nanodiamond surfaces},
author = {Torsten Gaebel and David Reilly and Ewa Rej and David Waddington},
year = {2017},
date = {2017-01-01},
publisher = {American Chemical Society},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Colless, James; Mahoney, Alice Charlotte; Pauka, Sebastian; Reilly, David; Fox, Eli J; Goldhaber-Gordon, David; Kou, Xufeng; Pan, Lei; Peeters, Lucas; Wang, Kang L
Zero-field edge plasmons in a magnetic topological insulator Journal Article
In: 2017.
@article{colless2017zero,
title = {Zero-field edge plasmons in a magnetic topological insulator},
author = {James Colless and Alice Charlotte Mahoney and Sebastian Pauka and David Reilly and Eli J Fox and David Goldhaber-Gordon and Xufeng Kou and Lei Pan and Lucas Peeters and Kang L Wang},
year = {2017},
date = {2017-01-01},
publisher = {Nature Publishing Group},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
2016
Ball, Harrison; Oliver, William D; Biercuk, Michael J
The role of master clock stability in quantum information processing Journal Article
In: npj Quantum Information, vol. 2, no. 1, pp. 16033, 2016.
BibTeX | Links:
@article{Ball2016,
title = {The role of master clock stability in quantum information processing},
author = {Harrison Ball and William D Oliver and Michael J Biercuk},
doi = {10.1038/npjqi.2016.33},
year = {2016},
date = {2016-01-01},
journal = {npj Quantum Information},
volume = {2},
number = {1},
pages = {16033},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Rej, Ewa; Gaebel, Torsten; Waddington, David E J; Reilly, David J
Hyperpolarized Nanodiamond Surfaces Journal Article
In: Journal of the American Chemical Society, 2016, ISSN: 0002-7863.
BibTeX | Links:
@article{Rej2016,
title = {Hyperpolarized Nanodiamond Surfaces},
author = {Ewa Rej and Torsten Gaebel and David E J Waddington and David J Reilly},
url = {https://newapp.readcube.com/library/91063203-0e68-43c4-9bfb-057b95692169/item/9B4F7B20-7153-805F-CFF3-9A01B38E8E00},
doi = {10.1021/jacs.6b09293},
issn = {0002-7863},
year = {2016},
date = {2016-01-01},
journal = {Journal of the American Chemical Society},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Tuckerman, David B.; Hamilton, Michael C.; Reilly, David J.; Bai, Rujun; Hernandez, George A.; Hornibrook, John M.; Sellers, John A.; Ellis, Charles D.
Flexible superconducting Nb transmission lines on thin film polyimide for quantum computing applications Journal Article
In: Superconductor Science and Technology, vol. 29, iss. 8, 2016, ISSN: 13616668.
@article{Tuckerman2016,
title = {Flexible superconducting Nb transmission lines on thin film polyimide for quantum computing applications},
author = {David B. Tuckerman and Michael C. Hamilton and David J. Reilly and Rujun Bai and George A. Hernandez and John M. Hornibrook and John A. Sellers and Charles D. Ellis},
doi = {10.1088/0953-2048/29/8/084007},
issn = {13616668},
year = {2016},
date = {2016-01-01},
journal = {Superconductor Science and Technology},
volume = {29},
issue = {8},
publisher = {Institute of Physics Publishing},
abstract = {We describe progress and initial results achieved towards the goal of developing integrated multi-conductor arrays of shielded controlled-impedance flexible superconducting transmission lines with ultra-miniature cross sections and wide bandwidths (dc to >10 GHz) over meter-scale lengths. Intended primarily for use in future scaled-up quantum computing systems, such flexible thin-film niobium/polyimide ribbon cables could provide a physically compact and ultra-low thermal conductance alternative to the rapidly increasing number of discrete coaxial cables that are currently used by quantum computing experimentalists to transmit signals between the several low-temperature stages (from ∼4 K down to ∼20 mK) of a dilution refrigerator. We have concluded that these structures are technically feasible to fabricate, and so far they have exhibited acceptable thermo-mechanical reliability. S-parameter results are presented for individual 2-metal layer Nb microstrip structures having 50 Ω characteristic impedance; lengths ranging from 50 to 550 mm were successfully fabricated. Solderable pads at the end terminations allowed testing using conventional rf connectors. Weakly coupled open-circuit microstrip resonators provided a sensitive measure of the overall transmission line loss as a function of frequency, temperature, and power. Two common microelectronic-grade polyimide dielectrics, one conventional and the other photo-definable (PI-2611 and HD-4100, respectively) were compared. Our most striking result, not previously reported to our knowledge, was that the dielectric loss tangents of both polyimides, over frequencies from 1 to 20 GHz, are remarkably low at deep cryogenic temperatures, typically 100x smaller than corresponding room temperature values. This enables fairly long-distance (meter-scale) transmission of microwave signals without excessive attenuation, and also permits usefully high rf power levels to be transmitted without creating excessive dielectric heating. We observed loss tangents as low as 2.2 × 10-5 at 20 mK, although losses increased somewhat at very low rf power levels, similar to the well-known behavior of amorphous inorganic dielectrics such as SiO2. Our fabrication techniques could be extended to more complex structures such as multiconductor cables, embedded microstrip, 3-metal layer stripline or rectangular coax, and integrated attenuators and thermalization structures.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We describe progress and initial results achieved towards the goal of developing integrated multi-conductor arrays of shielded controlled-impedance flexible superconducting transmission lines with ultra-miniature cross sections and wide bandwidths (dc to >10 GHz) over meter-scale lengths. Intended primarily for use in future scaled-up quantum computing systems, such flexible thin-film niobium/polyimide ribbon cables could provide a physically compact and ultra-low thermal conductance alternative to the rapidly increasing number of discrete coaxial cables that are currently used by quantum computing experimentalists to transmit signals between the several low-temperature stages (from ∼4 K down to ∼20 mK) of a dilution refrigerator. We have concluded that these structures are technically feasible to fabricate, and so far they have exhibited acceptable thermo-mechanical reliability. S-parameter results are presented for individual 2-metal layer Nb microstrip structures having 50 Ω characteristic impedance; lengths ranging from 50 to 550 mm were successfully fabricated. Solderable pads at the end terminations allowed testing using conventional rf connectors. Weakly coupled open-circuit microstrip resonators provided a sensitive measure of the overall transmission line loss as a function of frequency, temperature, and power. Two common microelectronic-grade polyimide dielectrics, one conventional and the other photo-definable (PI-2611 and HD-4100, respectively) were compared. Our most striking result, not previously reported to our knowledge, was that the dielectric loss tangents of both polyimides, over frequencies from 1 to 20 GHz, are remarkably low at deep cryogenic temperatures, typically 100x smaller than corresponding room temperature values. This enables fairly long-distance (meter-scale) transmission of microwave signals without excessive attenuation, and also permits usefully high rf power levels to be transmitted without creating excessive dielectric heating. We observed loss tangents as low as 2.2 × 10-5 at 20 mK, although losses increased somewhat at very low rf power levels, similar to the well-known behavior of amorphous inorganic dielectrics such as SiO2. Our fabrication techniques could be extended to more complex structures such as multiconductor cables, embedded microstrip, 3-metal layer stripline or rectangular coax, and integrated attenuators and thermalization structures.
Ball, Harrison; Oliver, William D; Biercuk, Michael J
The role of master clock stability in quantum information processing Journal Article
In: npj Quantum Information, vol. 2, no. 1, pp. 16033, 2016.
@article{Ball.2016lq8,
title = {The role of master clock stability in quantum information processing},
author = {Harrison Ball and William D Oliver and Michael J Biercuk},
url = {http://www.nature.com/articles/npjqi201633?WT.ec_id=NPJQI-201611&spMailingID=52876976&spUserID=MTc5OTg2NTM4NTc4S0&spJobID=1048210951&spReportId=MTA0ODIxMDk1MQS2},
doi = {10.1038/npjqi.2016.33},
year = {2016},
date = {2016-01-01},
journal = {npj Quantum Information},
volume = {2},
number = {1},
pages = {16033},
abstract = {Experimentalists seeking to improve the coherent lifetimes of quantum bits have generally focused on mitigating decoherence mechanisms through, for example, improvements to qubit designs and materials, and system isolation from environmental perturbations. In the case of the phase degree of freedom in a quantum superposition, however, the coherence that must be preserved is not solely internal to the qubit, but rather necessarily includes that of the qubit relative to the ‘master clock’ (e.g., a local oscillator) that governs its control system. In this manuscript, we articulate the impact of instabilities in the master clock on qubit phase coherence and provide tools to calculate the contributions to qubit error arising from these processes. We first connect standard oscillator phase-noise metrics to their corresponding qubit dephasing spectral densities. We then use representative lab-grade and performance-grade oscillator specifications to calculate operational fidelity bounds on trapped-ion and superconducting qubits with relatively slow and fast operation times. We discuss the relevance of these bounds for quantum error correction in contemporary experiments and future large-scale quantum information systems, and consider potential means to improve master clock stability.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Experimentalists seeking to improve the coherent lifetimes of quantum bits have generally focused on mitigating decoherence mechanisms through, for example, improvements to qubit designs and materials, and system isolation from environmental perturbations. In the case of the phase degree of freedom in a quantum superposition, however, the coherence that must be preserved is not solely internal to the qubit, but rather necessarily includes that of the qubit relative to the ‘master clock’ (e.g., a local oscillator) that governs its control system. In this manuscript, we articulate the impact of instabilities in the master clock on qubit phase coherence and provide tools to calculate the contributions to qubit error arising from these processes. We first connect standard oscillator phase-noise metrics to their corresponding qubit dephasing spectral densities. We then use representative lab-grade and performance-grade oscillator specifications to calculate operational fidelity bounds on trapped-ion and superconducting qubits with relatively slow and fast operation times. We discuss the relevance of these bounds for quantum error correction in contemporary experiments and future large-scale quantum information systems, and consider potential means to improve master clock stability.
Ball, Harrison; Stace, Thomas M; Flammia, Steven T; Biercuk, Michael J
Effect of noise correlations on randomized benchmarking Journal Article
In: Physical Review A, vol. 93, no. 2, pp. 022303, 2016, ISSN: 2469-9926.
@article{Ball.2016b,
title = {Effect of noise correlations on randomized benchmarking},
author = {Harrison Ball and Thomas M Stace and Steven T Flammia and Michael J Biercuk},
url = {http://journals.aps.org/pra/abstract/10.1103/PhysRevA.93.022303},
doi = {10.1103/physreva.93.022303},
issn = {2469-9926},
year = {2016},
date = {2016-01-01},
journal = {Physical Review A},
volume = {93},
number = {2},
pages = {022303},
abstract = {Among the most popular and well-studied quantum characterization, verification, and validation techniques is randomized benchmarking (RB), an important statistical tool used to characterize the performance of physical logic operations useful in quantum information processing. In this work we provide a detailed mathematical treatment of the effect of temporal noise correlations on the outcomes of RB protocols. We provide a fully analytic framework capturing the accumulation of error in RB expressed in terms of a three-dimensional random walk in “Pauli space.” Using this framework we derive the probability density function describing RB outcomes (averaged over noise) for both Markovian and correlated errors, which we show is generally described by a Γ distribution with shape and scale parameters depending on the correlation structure. Long temporal correlations impart large nonvanishing variance and skew in the distribution towards high-fidelity outcomes—consistent with existing experimental data—highlighting potential finite-sampling pitfalls and the divergence of the mean RB outcome from worst-case errors in the presence of noise correlations. We use the filter-transfer function formalism to reveal the underlying reason for these differences in terms of effective coherent averaging of correlated errors in certain random sequences. We conclude by commenting on the impact of these calculations on the utility of single-metric approaches to quantum characterization, verification, and validation.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Among the most popular and well-studied quantum characterization, verification, and validation techniques is randomized benchmarking (RB), an important statistical tool used to characterize the performance of physical logic operations useful in quantum information processing. In this work we provide a detailed mathematical treatment of the effect of temporal noise correlations on the outcomes of RB protocols. We provide a fully analytic framework capturing the accumulation of error in RB expressed in terms of a three-dimensional random walk in “Pauli space.” Using this framework we derive the probability density function describing RB outcomes (averaged over noise) for both Markovian and correlated errors, which we show is generally described by a Γ distribution with shape and scale parameters depending on the correlation structure. Long temporal correlations impart large nonvanishing variance and skew in the distribution towards high-fidelity outcomes—consistent with existing experimental data—highlighting potential finite-sampling pitfalls and the divergence of the mean RB outcome from worst-case errors in the presence of noise correlations. We use the filter-transfer function formalism to reveal the underlying reason for these differences in terms of effective coherent averaging of correlated errors in certain random sequences. We conclude by commenting on the impact of these calculations on the utility of single-metric approaches to quantum characterization, verification, and validation.
Britton, J W; Bohnet, J G; Sawyer, B C; Uys, H; Biercuk, M J; Bollinger, J J
Vibration-induced field fluctuations in a superconducting magnet Journal Article
In: Physical Review A, vol. 93, no. 6, pp. 062511, 2016, ISSN: 2469-9926.
@article{Britton.2016,
title = {Vibration-induced field fluctuations in a superconducting magnet},
author = {J W Britton and J G Bohnet and B C Sawyer and H Uys and M J Biercuk and J J Bollinger},
url = {https://journals.aps.org/pra/abstract/10.1103/PhysRevA.93.062511},
doi = {10.1103/physreva.93.062511},
issn = {2469-9926},
year = {2016},
date = {2016-01-01},
journal = {Physical Review A},
volume = {93},
number = {6},
pages = {062511},
abstract = {Superconducting magnets enable precise control of nuclear and electron spins, and are used in experiments that explore biological and condensed-matter systems, and fundamental atomic particles. In high-precision applications, a common view is that slow (<1Hz) drift of the homogeneous magnetic-field limits control and measurement precision. We report on previously undocumented higher-frequency field noise (10–200 Hz) that limits the coherence time of Be+9 electron-spin qubits in the 4.46-T field of a superconducting magnet. We measure a spin-echo T2 coherence time of ∼6ms for the Be+9 electron-spin resonance at 124GHz, limited by part-per-billion fractional fluctuations in the magnet's homogeneous field. Vibration isolation of the magnet improved T2 to ∼50 ms.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Superconducting magnets enable precise control of nuclear and electron spins, and are used in experiments that explore biological and condensed-matter systems, and fundamental atomic particles. In high-precision applications, a common view is that slow (<1Hz) drift of the homogeneous magnetic-field limits control and measurement precision. We report on previously undocumented higher-frequency field noise (10–200 Hz) that limits the coherence time of Be+9 electron-spin qubits in the 4.46-T field of a superconducting magnet. We measure a spin-echo T2 coherence time of ∼6ms for the Be+9 electron-spin resonance at 124GHz, limited by part-per-billion fractional fluctuations in the magnet’s homogeneous field. Vibration isolation of the magnet improved T2 to ∼50 ms.
Ball, Harrison; Nguyen, Trung; Leong, Philip H W; Biercuk, Michael J
Functional Basis for Efficient Physical Layer Classical Control in Quantum Processors Journal Article
In: Physical Review Applied, vol. 6, no. 6, pp. 064009, 2016, ISSN: 2331-7019.
@article{Ball.2016gh5,
title = {Functional Basis for Efficient Physical Layer Classical Control in Quantum Processors},
author = {Harrison Ball and Trung Nguyen and Philip H W Leong and Michael J Biercuk},
url = {http://journals.aps.org/prapplied/abstract/10.1103/PhysRevApplied.6.064009?utm_source=email&utm_medium=email&utm_campaign=prapplied-alert},
doi = {10.1103/physrevapplied.6.064009},
issn = {2331-7019},
year = {2016},
date = {2016-01-01},
journal = {Physical Review Applied},
volume = {6},
number = {6},
pages = {064009},
abstract = {The rapid progress seen in the development of quantum-coherent devices for information processing has motivated serious consideration of quantum computer architecture and organization. One topic which remains open for investigation and optimization relates to the design of the classical-quantum interface, where control operations on individual qubits are applied according to higher-level algorithms; accommodating competing demands on performance and scalability remains a major outstanding challenge. In this work, we present a resource-efficient, scalable framework for the implementation of embedded physical layer classical controllers for quantum-information systems. Design drivers and key functionalities are introduced, leading to the selection of Walsh functions as an effective functional basis for both programing and controller hardware implementation. This approach leverages the simplicity of real-time Walsh-function generation in classical digital hardware, and the fact that a wide variety of physical layer controls, such as dynamic error suppression, are known to fall within the Walsh family. We experimentally implement a real-time field-programmable-gate-array-based Walsh controller producing Walsh timing signals and Walsh-synthesized analog waveforms appropriate for critical tasks in error-resistant quantum control and noise characterization. These demonstrations represent the first step towards a unified framework for the realization of physical layer controls compatible with large-scale quantum-information processing.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The rapid progress seen in the development of quantum-coherent devices for information processing has motivated serious consideration of quantum computer architecture and organization. One topic which remains open for investigation and optimization relates to the design of the classical-quantum interface, where control operations on individual qubits are applied according to higher-level algorithms; accommodating competing demands on performance and scalability remains a major outstanding challenge. In this work, we present a resource-efficient, scalable framework for the implementation of embedded physical layer classical controllers for quantum-information systems. Design drivers and key functionalities are introduced, leading to the selection of Walsh functions as an effective functional basis for both programing and controller hardware implementation. This approach leverages the simplicity of real-time Walsh-function generation in classical digital hardware, and the fact that a wide variety of physical layer controls, such as dynamic error suppression, are known to fall within the Walsh family. We experimentally implement a real-time field-programmable-gate-array-based Walsh controller producing Walsh timing signals and Walsh-synthesized analog waveforms appropriate for critical tasks in error-resistant quantum control and noise characterization. These demonstrations represent the first step towards a unified framework for the realization of physical layer controls compatible with large-scale quantum-information processing.
2015
Rej, Ewa; Gaebel, Torsten; Boele, Thomas; Waddington, David E J; Reilly, David J
Hyperpolarized Nanodiamond with Long Spin Relaxation Times Journal Article
In: arXiv, 2015.
@article{Rej2015,
title = {Hyperpolarized Nanodiamond with Long Spin Relaxation Times},
author = {Ewa Rej and Torsten Gaebel and Thomas Boele and David E J Waddington and David J Reilly},
url = {https://newapp.readcube.com/library/91063203-0e68-43c4-9bfb-057b95692169/item/b14011ee-d75a-4b7a-805d-bd5a5a2d391b},
doi = {10.1038/ncomms9459},
year = {2015},
date = {2015-01-01},
journal = {arXiv},
abstract = {The use of hyperpolarized agents in magnetic resonance (MR), such as 13C-labeled compounds, enables powerful new imaging and detection modalities that stem from a 10,000-fold boost in signal. A major challenge for the future of the hyperpolarizaton technique is the inherently short spin relaxation times, typically < 60 seconds for 13C liquid-state compounds, which limit the time that the signal remains boosted. Here, we demonstrate that 1.1% natural abundance 13C spins in synthetic nanodiamond (ND) can be hyperpolarized at cryogenic and room temperature without the use of toxic free- radicals, and, owing to their solid-state environment, exhibit relaxation times exceeding 1 hour. Combined with the already established applications of NDs in the life-sciences as inexpensive fluorescent markers and non-cytotoxic substrates for gene and drug delivery, these results extend the theranostic capabilities of nanoscale diamonds into the domain of hyperpolarized MR.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The use of hyperpolarized agents in magnetic resonance (MR), such as 13C-labeled compounds, enables powerful new imaging and detection modalities that stem from a 10,000-fold boost in signal. A major challenge for the future of the hyperpolarizaton technique is the inherently short spin relaxation times, typically < 60 seconds for 13C liquid-state compounds, which limit the time that the signal remains boosted. Here, we demonstrate that 1.1% natural abundance 13C spins in synthetic nanodiamond (ND) can be hyperpolarized at cryogenic and room temperature without the use of toxic free- radicals, and, owing to their solid-state environment, exhibit relaxation times exceeding 1 hour. Combined with the already established applications of NDs in the life-sciences as inexpensive fluorescent markers and non-cytotoxic substrates for gene and drug delivery, these results extend the theranostic capabilities of nanoscale diamonds into the domain of hyperpolarized MR.
Ball, Harrison; Biercuk, Michael J
Walsh-synthesized noise filters for quantum logic Journal Article
In: EPJ Quantum Technology, vol. 2, no. 1, pp. 11, 2015.
@article{Ball.2015,
title = {Walsh-synthesized noise filters for quantum logic},
author = {Harrison Ball and Michael J Biercuk},
url = {https://epjquantumtechnology.springeropen.com/articles/10.1140/epjqt/s40507-015-0022-4},
doi = {10.1140/epjqt/s40507-015-0022-4},
year = {2015},
date = {2015-01-01},
journal = {EPJ Quantum Technology},
volume = {2},
number = {1},
pages = {11},
abstract = {We study a novel class of open-loop control protocols constructed to perform arbitrary nontrivial single-qubit logic operations robust against time-dependent non-Markovian noise. Amplitude and phase modulation protocols are crafted leveraging insights from functional synthesis and the basis set of Walsh functions. We employ the experimentally validated generalized filter-transfer function formalism in order to find optimized control protocols for target operations in SU(2) by defining a cost function for the filter-transfer function to be minimized through the applied modulation. Our work details the various techniques by which we define and then optimize the filter-synthesis process in the Walsh basis, including the definition of specific analytic design rules which serve to efficiently constrain the available synthesis space. This approach yields modulated-gate constructions consisting of chains of discrete pulse-segments of arbitrary form, whose modulation envelopes possess intrinsic compatibility with digital logic and clocking. We derive novel families of Walsh-modulated noise filters designed to suppress dephasing and coherent amplitude-damping noise, and describe how well-known sequences derived in NMR also fall within the Walsh-synthesis framework. Finally, our work considers the effects of realistic experimental constraints such as limited modulation bandwidth on achievable filter performance.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We study a novel class of open-loop control protocols constructed to perform arbitrary nontrivial single-qubit logic operations robust against time-dependent non-Markovian noise. Amplitude and phase modulation protocols are crafted leveraging insights from functional synthesis and the basis set of Walsh functions. We employ the experimentally validated generalized filter-transfer function formalism in order to find optimized control protocols for target operations in SU(2) by defining a cost function for the filter-transfer function to be minimized through the applied modulation. Our work details the various techniques by which we define and then optimize the filter-synthesis process in the Walsh basis, including the definition of specific analytic design rules which serve to efficiently constrain the available synthesis space. This approach yields modulated-gate constructions consisting of chains of discrete pulse-segments of arbitrary form, whose modulation envelopes possess intrinsic compatibility with digital logic and clocking. We derive novel families of Walsh-modulated noise filters designed to suppress dephasing and coherent amplitude-damping noise, and describe how well-known sequences derived in NMR also fall within the Walsh-synthesis framework. Finally, our work considers the effects of realistic experimental constraints such as limited modulation bandwidth on achievable filter performance.
Fogarty, M A; Veldhorst, M; Harper, R; Yang, C H; Bartlett, S D; Flammia, S T; Dzurak, A S
Nonexponential fidelity decay in randomized benchmarking with low-frequency noise Journal Article
In: Physical Review A, vol. 92, no. 2, pp. 022326, 2015, ISSN: 1050-2947.
@article{Fogarty.2015,
title = {Nonexponential fidelity decay in randomized benchmarking with low-frequency noise},
author = {M A Fogarty and M Veldhorst and R Harper and C H Yang and S D Bartlett and S T Flammia and A S Dzurak},
url = {http://journals.aps.org/pra/abstract/10.1103/PhysRevA.92.022326},
doi = {10.1103/physreva.92.022326},
issn = {1050-2947},
year = {2015},
date = {2015-01-01},
journal = {Physical Review A},
volume = {92},
number = {2},
pages = {022326},
abstract = {We show that nonexponential fidelity decays in randomized benchmarking experiments on quantum-dot qubits are consistent with numerical simulations that incorporate low-frequency noise and correspond to a control fidelity that varies slowly with time. By expanding standard randomized benchmarking analysis to this experimental regime, we find that such nonexponential decays are better modeled by multiple exponential decay rates, leading to an instantaneous control fidelity for isotopically purified silicon metal-oxide-semiconductor quantum-dot qubits which is 98.9% when the low-frequency noise causes large detuning but can be as high as 99.9% when the qubit is driven on resonance and system calibrations are favorable. These advances in qubit characterization and validation methods underpin the considerable prospects for silicon as a qubit platform for fault-tolerant quantum computation.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We show that nonexponential fidelity decays in randomized benchmarking experiments on quantum-dot qubits are consistent with numerical simulations that incorporate low-frequency noise and correspond to a control fidelity that varies slowly with time. By expanding standard randomized benchmarking analysis to this experimental regime, we find that such nonexponential decays are better modeled by multiple exponential decay rates, leading to an instantaneous control fidelity for isotopically purified silicon metal-oxide-semiconductor quantum-dot qubits which is 98.9% when the low-frequency noise causes large detuning but can be as high as 99.9% when the qubit is driven on resonance and system calibrations are favorable. These advances in qubit characterization and validation methods underpin the considerable prospects for silicon as a qubit platform for fault-tolerant quantum computation.
Rej, Ewa; Gaebel, Torsten; Boele, Thomas; Waddington, David EJ; Reilly, David J
Hyperpolarized nanodiamond with long spin-relaxation times Journal Article
In: Nature communications, vol. 6, no. 1, pp. 8459, 2015.
@article{rej2015hyperpolarized,
title = {Hyperpolarized nanodiamond with long spin-relaxation times},
author = {Ewa Rej and Torsten Gaebel and Thomas Boele and David EJ Waddington and David J Reilly},
year = {2015},
date = {2015-01-01},
journal = {Nature communications},
volume = {6},
number = {1},
pages = {8459},
publisher = {Nature Publishing Group UK London},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Reilly, David J
Engineering the quantum-classical interface of solid-state qubits Journal Article
In: npj Quantum Information, vol. 1, no. 1, pp. 1–10, 2015.
@article{reilly2015engineering,
title = {Engineering the quantum-classical interface of solid-state qubits},
author = {David J Reilly},
year = {2015},
date = {2015-01-01},
journal = {npj Quantum Information},
volume = {1},
number = {1},
pages = {1–10},
publisher = {Nature Publishing Group},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Hornibrook, JM; Colless, JI; Lamb, ID Conway; Pauka, SJ; Lu, H; Gossard, AC; Watson, JD; Gardner, GC; Fallahi, S; Manfra, MJ; others,
Cryogenic control architecture for large-scale quantum computing Journal Article
In: Physical Review Applied, vol. 3, no. 2, pp. 024010, 2015.
@article{hornibrook2015cryogenic,
title = {Cryogenic control architecture for large-scale quantum computing},
author = {JM Hornibrook and JI Colless and ID Conway Lamb and SJ Pauka and H Lu and AC Gossard and JD Watson and GC Gardner and S Fallahi and MJ Manfra and others},
year = {2015},
date = {2015-01-01},
journal = {Physical Review Applied},
volume = {3},
number = {2},
pages = {024010},
publisher = {APS},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
2014
Green, Todd J; Biercuk, Michael J
Phase-Modulated Decoupling and Error Suppression in Qubit-Oscillator Systems Journal Article
In: Physical Review Letters, vol. 114, no. 12, pp. 120502, 2014, ISSN: 0031-9007.
@article{Green.2015,
title = {Phase-Modulated Decoupling and Error Suppression in Qubit-Oscillator Systems},
author = {Todd J Green and Michael J Biercuk},
url = {https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.114.120502},
doi = {10.1103/physrevlett.114.120502},
issn = {0031-9007},
year = {2014},
date = {2014-01-01},
journal = {Physical Review Letters},
volume = {114},
number = {12},
pages = {120502},
abstract = {We present a scheme designed to suppress the dominant source of infidelity in entangling gates between quantum systems coupled through intermediate bosonic oscillator modes. Such systems are particularly susceptible to residual qubit-oscillator entanglement at the conclusion of a gate period that reduces the fidelity of the target entangling operation. We demonstrate how the exclusive use of discrete shifts in the phase of the field moderating the qubit-oscillator interaction is sufficient to both ensure multiple oscillator modes are decoupled and to suppress the effects of fluctuations in the driving field. This approach is amenable to a wide variety of technical implementations including geometric phase gates in superconducting qubits and the Molmer-Sorensen gate for trapped ions. We present detailed example protocols tailored to trapped-ion experiments and demonstrate that our approach has the potential to enable multiqubit gate implementation with a significant reduction in technical complexity relative to previously demonstrated protocols.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We present a scheme designed to suppress the dominant source of infidelity in entangling gates between quantum systems coupled through intermediate bosonic oscillator modes. Such systems are particularly susceptible to residual qubit-oscillator entanglement at the conclusion of a gate period that reduces the fidelity of the target entangling operation. We demonstrate how the exclusive use of discrete shifts in the phase of the field moderating the qubit-oscillator interaction is sufficient to both ensure multiple oscillator modes are decoupled and to suppress the effects of fluctuations in the driving field. This approach is amenable to a wide variety of technical implementations including geometric phase gates in superconducting qubits and the Molmer-Sorensen gate for trapped ions. We present detailed example protocols tailored to trapped-ion experiments and demonstrate that our approach has the potential to enable multiqubit gate implementation with a significant reduction in technical complexity relative to previously demonstrated protocols.
Hayes, David; Flammia, Steven T; Biercuk, Michael J
Programmable quantum simulation by dynamic Hamiltonian engineering Journal Article
In: New Journal of Physics, vol. 16, no. 8, pp. 083027, 2014, ISSN: 1367-2630.
@article{Hayes.2014,
title = {Programmable quantum simulation by dynamic Hamiltonian engineering},
author = {David Hayes and Steven T Flammia and Michael J Biercuk},
url = {http://iopscience.iop.org/article/10.1088/1367-2630/16/8/083027},
doi = {10.1088/1367-2630/16/8/083027},
issn = {1367-2630},
year = {2014},
date = {2014-01-01},
journal = {New Journal of Physics},
volume = {16},
number = {8},
pages = {083027},
abstract = {Quantum simulation is a promising near term application for quantum information processors with the potential to solve computationally intractable problems using just a few dozen interacting qubits. A range of experimental platforms have recently demonstrated the basic functionality of quantum simulation applied to quantum magnetism, quantum phase transitions and relativistic quantum mechanics. However, in all cases, the physics of the underlying hardware restricts the achievable inter-particle interactions and forms a serious constraint on the versatility of the simulators. To broaden the scope of these analog devices, we develop a suite of pulse sequences that permit a user to efficiently realize average Hamiltonians that are beyond the native interactions of the system. Specifically, this approach permits the generation of all symmetrically coupled translation-invariant two-body Hamiltonians with homogeneous on-site terms, a class which includes all spin- XYZ chains, but generalized to include long-range couplings. Our work builds on previous work proving that universal simulation is possible using both entangling gates and single-qubit unitaries. We show that determining the appropriate 'program' of unitary pulse sequences which implements an arbitrary Hamiltonian transformation can be formulated as a linear program over functions defined by those pulse sequences, running in polynomial time and scaling efficiently in hardware resources. Our analysis extends from circuit model quantum information to adiabatic quantum evolutions, representing an important and broad-based success in applying functional analysis to the field of quantum information.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Quantum simulation is a promising near term application for quantum information processors with the potential to solve computationally intractable problems using just a few dozen interacting qubits. A range of experimental platforms have recently demonstrated the basic functionality of quantum simulation applied to quantum magnetism, quantum phase transitions and relativistic quantum mechanics. However, in all cases, the physics of the underlying hardware restricts the achievable inter-particle interactions and forms a serious constraint on the versatility of the simulators. To broaden the scope of these analog devices, we develop a suite of pulse sequences that permit a user to efficiently realize average Hamiltonians that are beyond the native interactions of the system. Specifically, this approach permits the generation of all symmetrically coupled translation-invariant two-body Hamiltonians with homogeneous on-site terms, a class which includes all spin- XYZ chains, but generalized to include long-range couplings. Our work builds on previous work proving that universal simulation is possible using both entangling gates and single-qubit unitaries. We show that determining the appropriate ‘program’ of unitary pulse sequences which implements an arbitrary Hamiltonian transformation can be formulated as a linear program over functions defined by those pulse sequences, running in polynomial time and scaling efficiently in hardware resources. Our analysis extends from circuit model quantum information to adiabatic quantum evolutions, representing an important and broad-based success in applying functional analysis to the field of quantum information.
Lee, Michael W; Jarratt, Marie Claire; Marciniak, Christian; Biercuk, Michael J
Frequency stabilization of a 369 nm diode laser by nonlinear spectroscopy of Ytterbium ions in a discharge Journal Article
In: Optics Express, vol. 22, no. 6, pp. 7210, 2014.
@article{Lee.20149r9,
title = {Frequency stabilization of a 369 nm diode laser by nonlinear spectroscopy of Ytterbium ions in a discharge},
author = {Michael W Lee and Marie Claire Jarratt and Christian Marciniak and Michael J Biercuk},
url = {http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-22-6-7210},
doi = {10.1364/oe.22.007210},
year = {2014},
date = {2014-01-01},
journal = {Optics Express},
volume = {22},
number = {6},
pages = {7210},
abstract = {We demonstrate stabilization of an ultraviolet diode laser via Doppler-free spectroscopy of Ytterbium ions in a discharge. Our technique employs polarization spectroscopy, which produces a natural dispersive lineshape whose zero-crossing is largely immune to environmental drifts, making this signal an ideal absolute frequency reference for Yb+ ion trapping experiments. We stabilize an external-cavity diode laser near 369 nm for cooling Yb+ ions, using amplitude modulated polarization spectroscopy and a commercial PID feedback system. We achieve stable, low-drift locking with a standard deviation of measured laser frequency ∼ 400 kHz over 10 minutes, limited by the instantaneous linewidth of the diode laser. These results and the simplicity of our optical setup makes our approach attractive for stabilization of laser sources in atomic physics applications.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We demonstrate stabilization of an ultraviolet diode laser via Doppler-free spectroscopy of Ytterbium ions in a discharge. Our technique employs polarization spectroscopy, which produces a natural dispersive lineshape whose zero-crossing is largely immune to environmental drifts, making this signal an ideal absolute frequency reference for Yb+ ion trapping experiments. We stabilize an external-cavity diode laser near 369 nm for cooling Yb+ ions, using amplitude modulated polarization spectroscopy and a commercial PID feedback system. We achieve stable, low-drift locking with a standard deviation of measured laser frequency ∼ 400 kHz over 10 minutes, limited by the instantaneous linewidth of the diode laser. These results and the simplicity of our optical setup makes our approach attractive for stabilization of laser sources in atomic physics applications.
Soare, A; Ball, H; Hayes, D; Sastrawan, J; Jarratt, M C; McLoughlin, J J; Zhen, X; Green, T J; Biercuk, M J
Experimental noise filtering by quantum control Journal Article
In: Nature Physics, vol. 10, no. 11, pp. 825–829, 2014, ISSN: 1745-2473.
@article{Soare.2014,
title = {Experimental noise filtering by quantum control},
author = {A Soare and H Ball and D Hayes and J Sastrawan and M C Jarratt and J J McLoughlin and X Zhen and T J Green and M J Biercuk},
url = {http://www.nature.com/nphys/journal/v10/n11/full/nphys3115.html},
doi = {10.1038/nphys3115},
issn = {1745-2473},
year = {2014},
date = {2014-01-01},
journal = {Nature Physics},
volume = {10},
number = {11},
pages = {825–829},
abstract = {Quantum technologies are extremely sensitive to environmental disturbance. Control techniques inspired by classical systems engineering allow selective filtering of the noise spectrum, suppressing time-varying noise over defined frequency bands. Extrinsic interference is routinely faced in systems engineering, and a common solution is to rely on a broad class of filtering techniques to afford stability to intrinsically unstable systems or isolate particular signals from a noisy background. Experimentalists leading the development of a new generation of quantum-enabled technologies similarly encounter time-varying noise in realistic laboratory settings. They face substantial challenges in either suppressing such noise for high-fidelity quantum operations1 or controllably exploiting it in quantum-enhanced sensing2,3,4 or system identification tasks 5,6, due to a lack of efficient, validated approaches to understanding and predicting quantum dynamics in the presence of realistic time-varying noise. In this work we use the theory of quantum control engineering7,8 and experiments with trapped 171Yb+ ions to study the dynamics of controlled quantum systems. Our results provide the first experimental validation of generalized filter-transfer functions casting arbitrary quantum control operations on qubits as noise spectral filters9,10. We demonstrate the utility of these constructs for directly predicting the evolution of a quantum state in a realistic noisy environment as well as for developing novel robust control and sensing protocols. These experiments provide a significant advance in our understanding of the physics underlying controlled quantum dynamics, and unlock new capabilities for the emerging field of quantum systems engineering.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Quantum technologies are extremely sensitive to environmental disturbance. Control techniques inspired by classical systems engineering allow selective filtering of the noise spectrum, suppressing time-varying noise over defined frequency bands. Extrinsic interference is routinely faced in systems engineering, and a common solution is to rely on a broad class of filtering techniques to afford stability to intrinsically unstable systems or isolate particular signals from a noisy background. Experimentalists leading the development of a new generation of quantum-enabled technologies similarly encounter time-varying noise in realistic laboratory settings. They face substantial challenges in either suppressing such noise for high-fidelity quantum operations1 or controllably exploiting it in quantum-enhanced sensing2,3,4 or system identification tasks 5,6, due to a lack of efficient, validated approaches to understanding and predicting quantum dynamics in the presence of realistic time-varying noise. In this work we use the theory of quantum control engineering7,8 and experiments with trapped 171Yb+ ions to study the dynamics of controlled quantum systems. Our results provide the first experimental validation of generalized filter-transfer functions casting arbitrary quantum control operations on qubits as noise spectral filters9,10. We demonstrate the utility of these constructs for directly predicting the evolution of a quantum state in a realistic noisy environment as well as for developing novel robust control and sensing protocols. These experiments provide a significant advance in our understanding of the physics underlying controlled quantum dynamics, and unlock new capabilities for the emerging field of quantum systems engineering.
Soare, A; Ball, H; Hayes, D; Zhen, X; Jarratt, M C; Sastrawan, J; Uys, H; Biercuk, M J
Experimental bath engineering for quantitative studies of quantum control Journal Article
In: Physical Review A, vol. 89, no. 4, pp. 042329, 2014, ISSN: 1050-2947.
@article{Soare.2014de3,
title = {Experimental bath engineering for quantitative studies of quantum control},
author = {A Soare and H Ball and D Hayes and X Zhen and M C Jarratt and J Sastrawan and H Uys and M J Biercuk},
url = {http://journals.aps.org/pra/abstract/10.1103/PhysRevA.89.042329},
doi = {10.1103/physreva.89.042329},
issn = {1050-2947},
year = {2014},
date = {2014-01-01},
journal = {Physical Review A},
volume = {89},
number = {4},
pages = {042329},
abstract = {We develop and demonstrate a technique to engineer universal unitary baths in quantum systems. Using the correspondence between unitary decoherence due to ambient environmental noise and errors in a control system for quantum bits, we show how a wide variety of relevant classical error models may be realized through in-phase or in-quadrature modulation on a vector signal generator producing a resonant carrier signal. We demonstrate our approach through high-bandwidth modulation of the 12.6-GHz carrier appropriate for trapped Yb171+ ions. Experiments demonstrate the reduction of coherent lifetime in the system in the presence of both engineered dephasing noise during free evolution and engineered amplitude noise during driven operations. In both cases, the observed reduction of coherent lifetimes matches well with quantitative models described herein. These techniques form the basis of a toolkit for quantitative tests of quantum control protocols, helping experimentalists characterize the performance of their quantum coherent systems.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We develop and demonstrate a technique to engineer universal unitary baths in quantum systems. Using the correspondence between unitary decoherence due to ambient environmental noise and errors in a control system for quantum bits, we show how a wide variety of relevant classical error models may be realized through in-phase or in-quadrature modulation on a vector signal generator producing a resonant carrier signal. We demonstrate our approach through high-bandwidth modulation of the 12.6-GHz carrier appropriate for trapped Yb171+ ions. Experiments demonstrate the reduction of coherent lifetime in the system in the presence of both engineered dephasing noise during free evolution and engineered amplitude noise during driven operations. In both cases, the observed reduction of coherent lifetimes matches well with quantitative models described herein. These techniques form the basis of a toolkit for quantitative tests of quantum control protocols, helping experimentalists characterize the performance of their quantum coherent systems.
Kabytayev, Chingiz; Green, Todd J; Khodjasteh, Kaveh; Biercuk, Michael J; Viola, Lorenza; Brown, Kenneth R
Robustness of composite pulses to time-dependent control noise Journal Article
In: Physical Review A, vol. 90, no. 1, pp. 012316, 2014, ISSN: 1050-2947.
@article{Kabytayev.2014,
title = {Robustness of composite pulses to time-dependent control noise},
author = {Chingiz Kabytayev and Todd J Green and Kaveh Khodjasteh and Michael J Biercuk and Lorenza Viola and Kenneth R Brown},
url = {http://journals.aps.org/pra/abstract/10.1103/PhysRevA.90.012316},
doi = {10.1103/physreva.90.012316},
issn = {1050-2947},
year = {2014},
date = {2014-01-01},
journal = {Physical Review A},
volume = {90},
number = {1},
pages = {012316},
abstract = {We study the performance of composite pulses in the presence of time-varying control noise on a single qubit. These protocols, originally devised only to correct for static, systematic errors, are shown to be robust to time-dependent non-Markovian noise in the control field up to frequencies as high as ∼10% of the Rabi frequency. Our study combines a generalized filter-function approach with asymptotic dc-limit calculations to give a simple analytic framework for error analysis applied to a number of composite-pulse sequences relevant to nuclear magnetic resonance as well as quantum information experiments. Results include examination of recently introduced concatenated composite pulses and dynamically corrected gates, demonstrating equivalent first-order suppression of time-dependent fluctuations in amplitude and/or detuning, as appropriate for the sequence in question. Our analytic results agree well with numerical simulations for realistic 1/f noise spectra with a roll-off to 1/f2, providing independent validation of our theoretical insights.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We study the performance of composite pulses in the presence of time-varying control noise on a single qubit. These protocols, originally devised only to correct for static, systematic errors, are shown to be robust to time-dependent non-Markovian noise in the control field up to frequencies as high as ∼10% of the Rabi frequency. Our study combines a generalized filter-function approach with asymptotic dc-limit calculations to give a simple analytic framework for error analysis applied to a number of composite-pulse sequences relevant to nuclear magnetic resonance as well as quantum information experiments. Results include examination of recently introduced concatenated composite pulses and dynamically corrected gates, demonstrating equivalent first-order suppression of time-dependent fluctuations in amplitude and/or detuning, as appropriate for the sequence in question. Our analytic results agree well with numerical simulations for realistic 1/f noise spectra with a roll-off to 1/f2, providing independent validation of our theoretical insights.
Colless, JI; Croot, XG; Stace, Thomas M; Doherty, Andrew C; Barrett, Sean D; Lu, H; Gossard, AC; Reilly, David J
Raman phonon emission in a driven double quantum dot Journal Article
In: Nature communications, vol. 5, no. 1, pp. 3716, 2014.
@article{colless2014raman,
title = {Raman phonon emission in a driven double quantum dot},
author = {JI Colless and XG Croot and Thomas M Stace and Andrew C Doherty and Sean D Barrett and H Lu and AC Gossard and David J Reilly},
year = {2014},
date = {2014-01-01},
journal = {Nature communications},
volume = {5},
number = {1},
pages = {3716},
publisher = {Nature Publishing Group UK London},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
2013
Green, Todd J; Sastrawan, Jarrah; Uys, Hermann; Biercuk, Michael J
Arbitrary quantum control of qubits in the presence of universal noise Journal Article
In: New Journal of Physics, vol. 15, no. 9, pp. 095004, 2013, ISSN: 1367-2630.
@article{Green.2013,
title = {Arbitrary quantum control of qubits in the presence of universal noise},
author = {Todd J Green and Jarrah Sastrawan and Hermann Uys and Michael J Biercuk},
url = {http://iopscience.iop.org/article/10.1088/1367-2630/15/9/095004/meta},
doi = {10.1088/1367-2630/15/9/095004},
issn = {1367-2630},
year = {2013},
date = {2013-01-01},
journal = {New Journal of Physics},
volume = {15},
number = {9},
pages = {095004},
abstract = {We address the problem of deriving analytic expressions for calculating universal decoherence-induced errors in qubits undergoing arbitrary, unitary, time-dependent quantum control protocols. We show that the fidelity of a control operation may be expressed in terms of experimentally relevant spectral characteristics of the noise and of the control, over all Cartesian directions. We formulate control matrices in the time domain to capture the effects of piecewise-constant control, and convert them to generalized Fourier-domain filter functions. These generalized filter functions may be derived for complex temporally modulated control protocols, accounting for susceptibility to rotations of the qubit state vector in three dimensions. Taken together, we show that this framework provides a computationally efficient means to calculate the effects of universal noise on arbitrary quantum control protocols, producing results comparable with those obtained via time-consuming simulations of Bloch vector evolution. As a concrete example, we apply our method to treating the problem of dynamical decoupling incorporating realistic control pulses of arbitrary duration or form, including the replacement of simple π-pulses with complex dynamically corrected gates.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We address the problem of deriving analytic expressions for calculating universal decoherence-induced errors in qubits undergoing arbitrary, unitary, time-dependent quantum control protocols. We show that the fidelity of a control operation may be expressed in terms of experimentally relevant spectral characteristics of the noise and of the control, over all Cartesian directions. We formulate control matrices in the time domain to capture the effects of piecewise-constant control, and convert them to generalized Fourier-domain filter functions. These generalized filter functions may be derived for complex temporally modulated control protocols, accounting for susceptibility to rotations of the qubit state vector in three dimensions. Taken together, we show that this framework provides a computationally efficient means to calculate the effects of universal noise on arbitrary quantum control protocols, producing results comparable with those obtained via time-consuming simulations of Bloch vector evolution. As a concrete example, we apply our method to treating the problem of dynamical decoupling incorporating realistic control pulses of arbitrary duration or form, including the replacement of simple π-pulses with complex dynamically corrected gates.
Medford, J; Beil, J; Taylor, J M; Bartlett, S D; Doherty, A C; Rashba, E I; DiVincenzo, D P; Lu, H; Gossard, A C; Marcus, C M
Self-consistent measurement and state tomography of an exchange-only spin qubit Journal Article
In: Nature Nanotechnology, vol. 8, no. 9, pp. 654–659, 2013, ISSN: 1748-3387.
@article{Medford.2013,
title = {Self-consistent measurement and state tomography of an exchange-only spin qubit},
author = {J Medford and J Beil and J M Taylor and S D Bartlett and A C Doherty and E I Rashba and D P DiVincenzo and H Lu and A C Gossard and C M Marcus},
url = {http://www.nature.com/nnano/journal/v8/n9/full/nnano.2013.168.html},
doi = {10.1038/nnano.2013.168},
issn = {1748-3387},
year = {2013},
date = {2013-01-01},
journal = {Nature Nanotechnology},
volume = {8},
number = {9},
pages = {654–659},
abstract = {Quantum-dot spin qubits characteristically use oscillating magnetic or electric fields, or quasi-static Zeeman field gradients, to realize full qubit control. For the case of three confined electrons, exchange interaction between two pairs allows qubit rotation around two axes, hence full control, using only electrostatic gates. Here, we report initialization, full control, and single-shot readout of a three-electron exchange-driven spin qubit. Control via the exchange interaction is fast, yielding a demonstrated 75 qubit rotations in less than 2 ns. Measurement and state tomography are performed using a maximum-likelihood estimator method, allowing decoherence, leakage out of the qubit state space, and measurement fidelity to be quantified. The methods developed here are generally applicable to systems with state leakage, noisy measurements and non-orthogonal control axes. Full control by electric gates can be accomplished in exchange-driven spin qubits.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Quantum-dot spin qubits characteristically use oscillating magnetic or electric fields, or quasi-static Zeeman field gradients, to realize full qubit control. For the case of three confined electrons, exchange interaction between two pairs allows qubit rotation around two axes, hence full control, using only electrostatic gates. Here, we report initialization, full control, and single-shot readout of a three-electron exchange-driven spin qubit. Control via the exchange interaction is fast, yielding a demonstrated 75 qubit rotations in less than 2 ns. Measurement and state tomography are performed using a maximum-likelihood estimator method, allowing decoherence, leakage out of the qubit state space, and measurement fidelity to be quantified. The methods developed here are generally applicable to systems with state leakage, noisy measurements and non-orthogonal control axes. Full control by electric gates can be accomplished in exchange-driven spin qubits.
Stace, Thomas M; Doherty, Andrew C; Reilly, David J
Dynamical steady states in driven quantum systems Journal Article
In: Physical Review Letters, vol. 111, no. 18, pp. 180602, 2013.
@article{stace2013dynamical,
title = {Dynamical steady states in driven quantum systems},
author = {Thomas M Stace and Andrew C Doherty and David J Reilly},
year = {2013},
date = {2013-01-01},
journal = {Physical Review Letters},
volume = {111},
number = {18},
pages = {180602},
publisher = {APS},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Cano, Jennifer; Doherty, Andrew C; Nayak, Chetan; Reilly, David J
Microwave absorption by a mesoscopic quantum Hall droplet Journal Article
In: Physical Review B, vol. 88, no. 16, pp. 165305, 2013.
@article{cano2013microwave,
title = {Microwave absorption by a mesoscopic quantum Hall droplet},
author = {Jennifer Cano and Andrew C Doherty and Chetan Nayak and David J Reilly},
year = {2013},
date = {2013-01-01},
journal = {Physical Review B},
volume = {88},
number = {16},
pages = {165305},
publisher = {APS},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Reilly, David J
And then there were three Journal Article
In: Nature Nanotechnology, vol. 8, no. 6, pp. 395–396, 2013.
@article{reilly2013and,
title = {And then there were three},
author = {David J Reilly},
year = {2013},
date = {2013-01-01},
journal = {Nature Nanotechnology},
volume = {8},
number = {6},
pages = {395–396},
publisher = {Nature Publishing Group UK London},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Colless, JI; Croot, XG; Stace, TM; Doherty, AC; Barrett, SD; Lu, H; Gossard, AC; Reilly, DJ
Stimulated Phonon Emission in a Driven Double Quantum Dot Journal Article
In: arXiv preprint arXiv:1305.5982, 2013.
@article{colless2013stimulated,
title = {Stimulated Phonon Emission in a Driven Double Quantum Dot},
author = {JI Colless and XG Croot and TM Stace and AC Doherty and SD Barrett and H Lu and AC Gossard and DJ Reilly},
year = {2013},
date = {2013-01-01},
journal = {arXiv preprint arXiv:1305.5982},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Colless, JI; Mahoney, AC; Hornibrook, JM; Doherty, AC; Lu, H; Gossard, AC; Reilly, DJ
Dispersive readout of a few-electron double quantum dot with fast rf gate sensors Journal Article
In: Physical review letters, vol. 110, no. 4, pp. 046805, 2013.
@article{colless2013dispersive,
title = {Dispersive readout of a few-electron double quantum dot with fast rf gate sensors},
author = {JI Colless and AC Mahoney and JM Hornibrook and AC Doherty and H Lu and AC Gossard and DJ Reilly},
year = {2013},
date = {2013-01-01},
journal = {Physical review letters},
volume = {110},
number = {4},
pages = {046805},
publisher = {APS},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
2012
Green, Todd; Uys, Hermann; Biercuk, Michael J
High-Order Noise Filtering in Nontrivial Quantum Logic Gates Journal Article
In: Physical Review Letters, vol. 109, no. 2, pp. 020501, 2012, ISSN: 0031-9007.
@article{Green.2012,
title = {High-Order Noise Filtering in Nontrivial Quantum Logic Gates},
author = {Todd Green and Hermann Uys and Michael J Biercuk},
url = {https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.109.020501},
doi = {10.1103/physrevlett.109.020501},
issn = {0031-9007},
year = {2012},
date = {2012-01-01},
journal = {Physical Review Letters},
volume = {109},
number = {2},
pages = {020501},
abstract = {Treating the effects of a time-dependent classical dephasing environment during quantum logic operations poses a theoretical challenge, as the application of noncommuting control operations gives rise to both dephasing and depolarization errors that must be accounted for in order to understand total average error rates. We develop a treatment based on effective Hamiltonian theory that allows us to efficiently model the effect of classical noise on nontrivial single-bit quantum logic operations composed of arbitrary control sequences. We present a general method to calculate the ensemble-averaged entanglement fidelity to arbitrary order in terms of noise filter functions, and provide explicit expressions to fourth order in the noise strength. In the weak noise limit we derive explicit filter functions for a broad class of piecewise-constant control sequences, and use them to study the performance of dynamically corrected gates, yielding good agreement with brute-force numerics.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Treating the effects of a time-dependent classical dephasing environment during quantum logic operations poses a theoretical challenge, as the application of noncommuting control operations gives rise to both dephasing and depolarization errors that must be accounted for in order to understand total average error rates. We develop a treatment based on effective Hamiltonian theory that allows us to efficiently model the effect of classical noise on nontrivial single-bit quantum logic operations composed of arbitrary control sequences. We present a general method to calculate the ensemble-averaged entanglement fidelity to arbitrary order in terms of noise filter functions, and provide explicit expressions to fourth order in the noise strength. In the weak noise limit we derive explicit filter functions for a broad class of piecewise-constant control sequences, and use them to study the performance of dynamically corrected gates, yielding good agreement with brute-force numerics.
Britton, Joseph W; Sawyer, Brian C; Keith, Adam C; Wang, Joseph C -C; Freericks, James K; Uys, Hermann; Biercuk, Michael J; Bollinger, John J
Engineered two-dimensional Ising interactions in a trapped-ion quantum simulator with hundreds of spins Journal Article
In: Nature, vol. 484, no. 7395, pp. 489–492, 2012, ISSN: 0028-0836.
@article{Britton.2012,
title = {Engineered two-dimensional Ising interactions in a trapped-ion quantum simulator with hundreds of spins},
author = {Joseph W Britton and Brian C Sawyer and Adam C Keith and Joseph C -C Wang and James K Freericks and Hermann Uys and Michael J Biercuk and John J Bollinger},
url = {http://www.nature.com/doifinder/10.1038/nature10981},
doi = {10.1038/nature10981},
issn = {0028-0836},
year = {2012},
date = {2012-01-01},
journal = {Nature},
volume = {484},
number = {7395},
pages = {489–492},
abstract = {A trapped-ion quantum simulator is used to demonstrate tunable long-range spin-spin couplings in two dimensions, relevant to studies of quantum magnetism at a scale that is intractable for classical computers. Quantum simulations could be used to study currently intractable many-body problems, such as quantum magnetism. However, technical challenges have so far limited simulations to a few tens of qubits, which is not enough to be computationally relevant. Here, Britton et al. demonstrate that a naturally occurring two-dimensional triangular crystal lattice of a few hundred beryllium ions held in an electromagnetic Penning trap can be used to simulate tunable antiferromagnetic interactions. This approach should bring the power of quantum simulation to a range of interesting problems in quantum magnetism. The presence of long-range quantum spin correlations underlies a variety of physical phenomena in condensed-matter systems, potentially including high-temperature superconductivity1,2. However, many properties of exotic, strongly correlated spin systems, such as spin liquids, have proved difficult to study, in part because calculations involving N-body entanglement become intractable for as few as N ≈ 30 particles3. Feynman predicted that a quantum simulator—a special-purpose ‘analogue’ processor built using quantum bits (qubits)—would be inherently suited to solving such problems4,5. In the context of quantum magnetism, a number of experiments have demonstrated the feasibility of this approach6,7,8,9,10,11,12,13,14, but simulations allowing controlled, tunable interactions between spins localized on two- or three-dimensional lattices of more than a few tens of qubits have yet to be demonstrated, in part because of the technical challenge of realizing large-scale qubit arrays. Here we demonstrate a variable-range Ising-type spin–spin interaction, Ji,j , on a naturally occurring, two-dimensional triangular crystal lattice of hundreds of spin-half particles (beryllium ions stored in a Penning trap). This is a computationally relevant scale more than an order of magnitude larger than previous experiments. We show that a spin-dependent optical dipole force can produce an antiferromagnetic interaction , where 0 ≤ a ≤ 3 and di,j is the distance between spin pairs. These power laws correspond physically to infinite-range (a = 0), Coulomb–like (a = 1), monopole–dipole (a = 2) and dipole–dipole (a = 3) couplings. Experimentally, we demonstrate excellent agreement with a theory for 0.05 ≲ a ≲ 1.4. This demonstration, coupled with the high spin count, excellent quantum control and low technical complexity of the Penning trap, brings within reach the simulation of otherwise computationally intractable problems in quantum magnetism.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
A trapped-ion quantum simulator is used to demonstrate tunable long-range spin-spin couplings in two dimensions, relevant to studies of quantum magnetism at a scale that is intractable for classical computers. Quantum simulations could be used to study currently intractable many-body problems, such as quantum magnetism. However, technical challenges have so far limited simulations to a few tens of qubits, which is not enough to be computationally relevant. Here, Britton et al. demonstrate that a naturally occurring two-dimensional triangular crystal lattice of a few hundred beryllium ions held in an electromagnetic Penning trap can be used to simulate tunable antiferromagnetic interactions. This approach should bring the power of quantum simulation to a range of interesting problems in quantum magnetism. The presence of long-range quantum spin correlations underlies a variety of physical phenomena in condensed-matter systems, potentially including high-temperature superconductivity1,2. However, many properties of exotic, strongly correlated spin systems, such as spin liquids, have proved difficult to study, in part because calculations involving N-body entanglement become intractable for as few as N ≈ 30 particles3. Feynman predicted that a quantum simulator—a special-purpose ‘analogue’ processor built using quantum bits (qubits)—would be inherently suited to solving such problems4,5. In the context of quantum magnetism, a number of experiments have demonstrated the feasibility of this approach6,7,8,9,10,11,12,13,14, but simulations allowing controlled, tunable interactions between spins localized on two- or three-dimensional lattices of more than a few tens of qubits have yet to be demonstrated, in part because of the technical challenge of realizing large-scale qubit arrays. Here we demonstrate a variable-range Ising-type spin–spin interaction, Ji,j , on a naturally occurring, two-dimensional triangular crystal lattice of hundreds of spin-half particles (beryllium ions stored in a Penning trap). This is a computationally relevant scale more than an order of magnitude larger than previous experiments. We show that a spin-dependent optical dipole force can produce an antiferromagnetic interaction , where 0 ≤ a ≤ 3 and di,j is the distance between spin pairs. These power laws correspond physically to infinite-range (a = 0), Coulomb–like (a = 1), monopole–dipole (a = 2) and dipole–dipole (a = 3) couplings. Experimentally, we demonstrate excellent agreement with a theory for 0.05 ≲ a ≲ 1.4. This demonstration, coupled with the high spin count, excellent quantum control and low technical complexity of the Penning trap, brings within reach the simulation of otherwise computationally intractable problems in quantum magnetism.
Blanvillain, S; Colless, JI; Reilly, DJ; Lu, H; Gossard, AC
Suppressing On-Chip EM Crosstalk for Spin Qubit Devices Journal Article
In: arXiv preprint arXiv:1205.4072, 2012.
@article{blanvillain2012suppressing,
title = {Suppressing On-Chip EM Crosstalk for Spin Qubit Devices},
author = {S Blanvillain and JI Colless and DJ Reilly and H Lu and AC Gossard},
year = {2012},
date = {2012-01-01},
journal = {arXiv preprint arXiv:1205.4072},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
2011
Biercuk, Michael J; Reilly, David J
Solid-state spins survive Journal Article
In: Nature Nanotechnology, vol. 6, no. 1, pp. 9–11, 2011.
@article{biercuk2011solid,
title = {Solid-state spins survive},
author = {Michael J Biercuk and David J Reilly},
year = {2011},
date = {2011-01-01},
journal = {Nature Nanotechnology},
volume = {6},
number = {1},
pages = {9–11},
publisher = {Nature Publishing Group UK London},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
2010
Cramer, Marcus; Plenio, Martin B; Flammia, Steven T; Somma, Rolando; Gross, David; Bartlett, Stephen D; Landon-Cardinal, Olivier; Poulin, David; Liu, Yi-Kai
Efficient quantum state tomography Journal Article
In: Nature Communications, vol. 1, no. 1, pp. 149, 2010.
@article{Cramer.2010,
title = {Efficient quantum state tomography},
author = {Marcus Cramer and Martin B Plenio and Steven T Flammia and Rolando Somma and David Gross and Stephen D Bartlett and Olivier Landon-Cardinal and David Poulin and Yi-Kai Liu},
url = {http://www.nature.com/ncomms/journal/v1/n9/abs/ncomms1147.html},
doi = {10.1038/ncomms1147},
year = {2010},
date = {2010-01-01},
journal = {Nature Communications},
volume = {1},
number = {1},
pages = {149},
abstract = {Quantum state tomography—deducing quantum states from measured data—is the gold standard for verification and benchmarking of quantum devices. It has been realized in systems with few components, but for larger systems it becomes unfeasible because the number of measurements and the amount of computation required to process them grows exponentially in the system size. Here, we present two tomography schemes that scale much more favourably than direct tomography with system size. One of them requires unitary operations on a constant number of subsystems, whereas the other requires only local measurements together with more elaborate post-processing. Both rely only on a linear number of experimental operations and post-processing that is polynomial in the system size. These schemes can be applied to a wide range of quantum states, in particular those that are well approximated by matrix product states. The accuracy of the reconstructed states can be rigorously certified without any a priori assumptions. Direct quantum state tomography—deducing the state of a system from measurements—is mostly unfeasible due to the exponential scaling of measurement number with system size. The authors present two new schemes, which scale linearly in this respect, and can be applied to a wide range of quantum states.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Quantum state tomography—deducing quantum states from measured data—is the gold standard for verification and benchmarking of quantum devices. It has been realized in systems with few components, but for larger systems it becomes unfeasible because the number of measurements and the amount of computation required to process them grows exponentially in the system size. Here, we present two tomography schemes that scale much more favourably than direct tomography with system size. One of them requires unitary operations on a constant number of subsystems, whereas the other requires only local measurements together with more elaborate post-processing. Both rely only on a linear number of experimental operations and post-processing that is polynomial in the system size. These schemes can be applied to a wide range of quantum states, in particular those that are well approximated by matrix product states. The accuracy of the reconstructed states can be rigorously certified without any a priori assumptions. Direct quantum state tomography—deducing the state of a system from measurements—is mostly unfeasible due to the exponential scaling of measurement number with system size. The authors present two new schemes, which scale linearly in this respect, and can be applied to a wide range of quantum states.
2009
Higgins, B L; Berry, D W; Bartlett, S D; Mitchell, M W; Wiseman, H M; Pryde, G J
Demonstrating Heisenberg-limited unambiguous phase estimation without adaptive measurements Journal Article
In: New Journal of Physics, vol. 11, no. 7, pp. 073023, 2009, ISSN: 1367-2630.
@article{Higgins.2009,
title = {Demonstrating Heisenberg-limited unambiguous phase estimation without adaptive measurements},
author = {B L Higgins and D W Berry and S D Bartlett and M W Mitchell and H M Wiseman and G J Pryde},
url = {http://iopscience.iop.org/article/10.1088/1367-2630/11/7/073023/meta;jsessionid=79AF7BFCB08ABBF6DA39FC4692A59A59.c4.iopscience.cld.iop.org},
doi = {10.1088/1367-2630/11/7/073023},
issn = {1367-2630},
year = {2009},
date = {2009-01-01},
journal = {New Journal of Physics},
volume = {11},
number = {7},
pages = {073023},
abstract = {We derive, and experimentally demonstrate, an interferometric scheme for unambiguous phase estimation with precision scaling at the Heisenberg limit that does not require adaptive measurements. That is, with no prior knowledge of the phase, we can obtain an estimate of the phase with a standard deviation that is only a small constant factor larger than the minimum physically allowed value. Our scheme resolves the phase ambiguity that exists when multiple passes through a phase shift, or NOON states, are used to obtain improved phase resolution. Like a recently introduced adaptive technique (Higgins et al 2007 Nature 450 393), our experiment uses multiple applications of the phase shift on single photons. By not requiring adaptive measurements, but rather using a predetermined measurement sequence, the present scheme is both conceptually simpler and significantly easier to implement. Additionally, we demonstrate a simplified adaptive scheme that also surpasses the standard quantum limit for single passes.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We derive, and experimentally demonstrate, an interferometric scheme for unambiguous phase estimation with precision scaling at the Heisenberg limit that does not require adaptive measurements. That is, with no prior knowledge of the phase, we can obtain an estimate of the phase with a standard deviation that is only a small constant factor larger than the minimum physically allowed value. Our scheme resolves the phase ambiguity that exists when multiple passes through a phase shift, or NOON states, are used to obtain improved phase resolution. Like a recently introduced adaptive technique (Higgins et al 2007 Nature 450 393), our experiment uses multiple applications of the phase shift on single photons. By not requiring adaptive measurements, but rather using a predetermined measurement sequence, the present scheme is both conceptually simpler and significantly easier to implement. Additionally, we demonstrate a simplified adaptive scheme that also surpasses the standard quantum limit for single passes.