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Models of environment and T_1 relaxation in Josephson Charge Qubits

Lara Faoro·Joakim Bergli·Boris L. Altshuler·Yuri M. Galperin
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Abstract

A theoretical interpretation of the recent experiments of Astafiev et. al. on the T_1-relaxation rate in Josephson Charge Qubits is proposed. The experimentally observed reproducible nonmonotonic dependence of T_1 on the splitting E_J of the qubit levels suggests further specification of the previously proposed models of the background charge noise. From our point of view the most promising is the ``Andreev fluctuator'' model of the noise. In this model the fluctuator is a Cooper pair that tunnels from a superconductor and occupies a pair of localized electronic states. Within this model one can naturally explain both the average linear T_1(E_J) dependence and the irregular fluctuations. The role of fluctuators in the formation of strong resonant peaks in this dependence is also discussed.

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Lara Faoro, Joakim Bergli, Boris L. Altshuler, Yuri M. Galperin. 2005-04-09. Models of environment and T_1 relaxation in Josephson Charge Qubits. https://doi.org/10.1103/physrevlett.95.046805

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