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Optimized dynamical decoupling in a model quantum memory


Any quantum system, such as those used in quantum information or magnetic resonance, is subject to random phase errors that can dramatically affect the fidelity of a desired quantum operation or measurement1. In the context of quantum information, quantum error correction techniques have been developed to correct these errors, but resource requirements are extraordinary. The realization of a physically tractable quantum information system will therefore be facilitated if qubit (quantum bit) error rates are far below the so-called fault-tolerance error threshold1, predicted to be of the order of 10-3–10-6. The need to realize such low error rates motivates a search for alternative strategies to suppress dephasing in quantum systems2. Here we experimentally demonstrate massive suppression of qubit error rates by the application of optimized dynamical decoupling3,4,5,6,7,8 pulse sequences, using a model quantum system capable of simulating a variety of qubit technologies. We demonstrate an analytically derived pulse sequence9, UDD, and find novel sequences through active, real-time experimental feedback. The latter sequences are tailored to maximize error suppression without the need for a priori knowledge of the ambient noise environment, and are capable of suppressing errors by orders of magnitude compared to other existing sequences (including the benchmark multi-pulse spin echo10,11). Our work includes the extension of a treatment to predict qubit decoherence12,13 under realistic conditions, yielding strong agreement between experimental data and theory for arbitrary pulse sequences incorporating nonidealized control pulses. These results demonstrate the robustness of qubit memory error suppression through dynamical decoupling techniques across a variety of qubit technologies11,14,15,16.

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Figure 1: CPMG and UDD pulse sequence schematics.
Figure 2: 9 Be + qubit structure and coherent control.
Figure 3: Pulse sequence performance in the presence of various noise spectra.
Figure 4: Nelder-Mead pulse-sequence optimization using Ohmic spectrum and n = 6.


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We thank L. Cywinski, S. Das Sarma, V. V. Dobrovitski, X. Hu, E. Knill, S. Lyon, G. Uhrig, and W. Witzel for discussions. We also thank D. Hanneke, C. Ospelkaus and D. J. Wineland for comments on the manuscript, and C. Nelson for technical assistance. We acknowledge research funding from IARPA and the NIST Quantum Information Program. M.J.B. acknowledges fellowship support from IARPA and Georgia Tech., and H.U. acknowledges support from CSIR. This manuscript is a contribution of the US NIST and is not subject to US copyright.

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Correspondence to Michael J. Biercuk.

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Biercuk, M., Uys, H., VanDevender, A. et al. Optimized dynamical decoupling in a model quantum memory. Nature 458, 996–1000 (2009).

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