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Compressed optimization of device architectures

Physical Review Applied

Frees, Adam; Foulk, James W.; Ward, Daniel R.; Blume-Kohout, Robin; Eriksson, M.A.; Friesen, Mark; Coppersmith, S.N.

Recent advances in nanotechnology have enabled researchers to control individual quantum mechanical objects with unprecedented accuracy, opening the door for both quantum and extreme-scale conventional computing applications. As these devices become larger and more complex, the ability to design them such that they can be simply controlled becomes a daunting and computationally infeasible task. Here, motivated by ideas from compressed sensing, we introduce a protocol for the Compressed Optimization of Device Architectures (CODA). It leads naturally to a metric for benchmarking device performance and optimizing device designs, and provides a scheme for automating the control of gate operations and reducing their complexity. Because CODA is computationally efficient, it is readily extensible to large systems. As a result, we demonstrate the CODA benchmarking and optimization protocols through simulations of up to eight quantum dots in devices that are currently being developed experimentally for quantum computation.

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TYPE Journal Article YEAR 2016
DOIOSTI

Minimax Quantum Tomography: Estimators and Relative Entropy Bounds

Physical Review Letters

Blume-Kohout, Robin; Ferrie, Christopher

A minimax estimator has the minimum possible error ("risk") in the worst case. We construct the first minimax estimators for quantum state tomography with relative entropy risk. The minimax risk of nonadaptive tomography scales as O(1/N) - in contrast to that of classical probability estimation, which is O(1/N) - where N is the number of copies of the quantum state used. We trace this deficiency to sampling mismatch: future observations that determine risk may come from a different sample space than the past data that determine the estimate. This makes minimax estimators very biased, and we propose a computationally tractable alternative with similar behavior in the worst case, but superior accuracy on most states.

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TYPE Journal Article YEAR 2016
DOIOSTIScopus

Micro-fabricated ion traps for Quantum Information Processing; Highlights and lessons learned

Maunz, Peter L.W.; Blume-Kohout, Robin; Blain, Matthew G.; Benito, Francisco; Berry, Christopher; Clark, Craig R.; Clark, Susan M.; Colombo, Anthony; Dagel, Amber; Fortier, Kevin; Haltli, Raymond A.; Heller, Edwin J.; Lobser, Daniel; Mizrahi, Jonathan; Nielsen, Erik N.; Resnick, Paul; Rembetski, John F.; Rudinger, Kenneth M.; Scrymgeour, David; Sterk, Jonathan D.; Tabakov, Boyan; Tigges, Chris P.; Van Der Wall, Jay W.; Stick, Daniel L.

Abstract not provided.

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TYPE Conference Poster YEAR 2015
OSTI

The Promise of Quantum Simulation

ACS Nano

Muller, Richard P.; Blume-Kohout, Robin

Quantum simulations promise to be one of the primary applications of quantum computers, should one be constructed. This article briefly summarizes the history of quantum simulation in light of the recent result of Wang and co-workers, demonstrating calculation of the ground and excited states for a HeH+ molecule, and concludes with a discussion of why this and other recent progress in the field suggest that quantum simulations of quantum chemistry have a bright future. (Figure Presented).

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TYPE Journal Article YEAR 2015
DOIOSTIScopus

Microwave-driven coherent operation of a semiconductor quantum dot charge qubit

Nature Nanotechnology

Foulk, James W.; Kim, Dohun; Ward, D.R.; Simmons, C.B.; Blume-Kohout, Robin; Nielsen, Erik N.; Savage, D.E.; Lagally, M.G.; Friesen, Mark; Coppersmith, S.N.; Eriksson, M.A.

An intuitive realization of a qubit is an electron charge at two well-defined positions of a double quantum dot. This qubit is simple and has the potential for high-speed operation because of its strong coupling to electric fields. However, charge noise also couples strongly to this qubit, resulting in rapid dephasing at all but one special operating point called the 'sweet spot'. In previous studies d.c. voltage pulses have been used to manipulate semiconductor charge qubits but did not achieve high-fidelity control, because d.c. gating requires excursions away from the sweet spot. Here, by using resonant a.c. microwave driving we achieve fast (greater than gigahertz) and universal single qubit rotations of a semiconductor charge qubit. The Z-axis rotations of the qubit are well protected at the sweet spot, and we demonstrate the same protection for rotations about arbitrary axes in the X-Y plane of the qubit Bloch sphere. We characterize the qubit operation using two tomographic approaches: standard process tomography and gate set tomography. Both methods consistently yield process fidelities greater than 86% with respect to a universal set of unitary single-qubit operations.

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TYPE Journal Article YEAR 2015
DOIOSTIScopus

Turbocharging Quantum Tomography

Blume-Kohout, Robin; Foulk, James W.; Nielsen, Erik N.; Maunz, Peter L.W.; Scholten, Travis L.; Rudinger, Kenneth M.

Quantum tomography is used to characterize quantum operations implemented in quantum information processing (QIP) hardware. Traditionally, state tomography has been used to characterize the quantum state prepared in an initialization procedure, while quantum process tomography is used to characterize dynamical operations on a QIP system. As such, tomography is critical to the development of QIP hardware (since it is necessary both for debugging and validating as-built devices, and its results are used to influence the next generation of devices). But tomography suffers from several critical drawbacks. In this report, we present new research that resolves several of these flaws. We describe a new form of tomography called gate set tomography (GST), which unifies state and process tomography, avoids prior methods critical reliance on precalibrated operations that are not generally available, and can achieve unprecedented accuracies. We report on theory and experimental development of adaptive tomography protocols that achieve far higher fidelity in state reconstruction than non-adaptive methods. Finally, we present a new theoretical and experimental analysis of process tomography on multispin systems, and demonstrate how to more effectively detect and characterize quantum noise using carefully tailored ensembles of input states.

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TYPE SAND Report YEAR 2014
DOIOSTI

Compressed optimization of device architectures

Foulk, James W.; Frees, Adam; Ward, Daniel R.; Blume-Kohout, Robin; Eriksson, M.A.; Friesen, Mark; Coppersmith, Susan N.

Recent advances in nanotechnology have enabled researchers to control individual quantum mechanical objects with unprecedented accuracy, opening the door for both quantum and extreme- scale conventional computation applications. As these devices become more complex, designing for facility of control becomes a daunting and computationally infeasible task. Here, motivated by ideas from compressed sensing, we introduce a protocol for the Compressed Optimization of Device Architectures (CODA). It leads naturally to a metric for benchmarking and optimizing device designs, as well as an automatic device control protocol that reduces the operational complexity required to achieve a particular output. Because this protocol is both experimentally and computationally efficient, it is readily extensible to large systems. For this paper, we demonstrate both the bench- marking and device control protocol components of CODA through examples of realistic simulations of electrostatic quantum dot devices, which are currently being developed experimentally for quantum computation.

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TYPE Journal Article YEAR 2014
OSTI
Results 101–150 of 174
Results 101–150 of 174