Month: June 2011

Dynamical decoupling noise spectroscopy | arXiv.org

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Dynamical decoupling noise spectroscopy

Gonzalo A. Alvarez, Dieter Suter

(Submitted on 17 Jun 2011 (v1), last revised 17 Sep 2011 (this version, v2))

Decoherence is one of the most important obstacles that must be overcome in quantum information processing. It depends on the qubit-environment coupling strength, but also on the spectral composition of the noise generated by the environment. If the spectral density is known, fighting the effect of decoherence can be made more effective. Applying sequences of inversion pulses to the qubit system, we generate effective filter functions that probe the environmental spectral density. Comparing different pulse sequences, we recover the complete spectral density function and distinguish different contributions to the overall decoherence.

Comments: 4+ pages, 3 figures. New experimental data was added. New references added

Subjects: Quantum Physics (quant-ph); Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Chemical Physics (physics.chem-ph)

Journal reference: Phys. Rev. Lett. 107, 230501 (2011)

DOI: 10.1103/PhysRevLett.107.230501

Cite as: arXiv:1106.3463v2 [quant-ph]

via [1106.3463] Dynamical decoupling noise spectroscopy.

Robust Dynamical Decoupling for Quantum Computing and Quantum Memory | Phys. Rev. Lett. 106, 240501 (2011)

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Robust Dynamical Decoupling for Quantum Computing and Quantum Memory

Alexandre M. Souza1, Gonzalo A. Álvarez1, and Dieter Suter1

1Fakultät Physik, Technische Universität Dortmund, D-44221, Dortmund, Germany

Received 21 March 2011; published 14 June 2011

Dynamical decoupling (DD) is a popular technique for protecting qubits from the environment. However, unless special care is taken, experimental errors in the control pulses used in this technique can destroy the quantum information instead of preserving it. Here, we investigate techniques for making DD sequences robust against different types of experimental errors while retaining good decoupling efficiency in a fluctuating environment. We present experimental data from solid-state nuclear spin qubits and introduce a new DD sequence that is suitable for quantum computing and quantum memory.

© 2011 American Physical Society

via Phys. Rev. Lett. 106, 240501 (2011): Robust Dynamical Decoupling for Quantum Computing and Quantum Memory.

Error tolerance of different DD sequences. The upper row shows the calculated fidelity F for standard DD sequences, while the lower row shows the results for the CPMG and PDD_1=XY-4 sequences when the \pi pulses are replaced by Knill pulses. The last panel corresponds to the KDD sequence, also based on the Knill pulse. Each panel shows the fidelity after 100 pulses as a function of flip-angle error and offset errors. The regions where the fidelity is lower than 0.95 are shown in white. The highest contour level is F=0.999.
Error tolerance of different DD sequences. The upper row shows the calculated fidelity F for standard DD sequences, while the lower row shows the results for the CPMG and PDD_1=XY-4 sequences when the pi pulses are replaced by Knill pulses. The last panel corresponds to the KDD sequence, also based on the Knill pulse. Each panel shows the fidelity after 100 pulses as a function of flip-angle error and offset errors. The regions where the fidelity is lower than 0.95 are shown in white. The highest contour level is F=0.999.