Nanosecond quantum state detection in a current-biased dc SQUID

被引：16
作者：
Claudon, J.
Fay, A.
Hoskinson, E.
Buisson, O.
机构：
[1] CNRS, Inst NEEL, F-38042 Grenoble, France
[2] Univ Grenoble 1, F-38042 Grenoble, France
来源：
PHYSICAL REVIEW B | 2007年 / 76卷 / 02期
关键词：
D O I：
10.1103/PhysRevB.76.024508
中图分类号：
T [工业技术];
学科分类号：
08 ;
摘要：
This paper presents our procedure to measure the quantum state of a dc superconducting quantum interference device (SQUID) within a few nanoseconds, using an adiabatic dc flux pulse. Detection of the ground state is governed by standard macroscopic quantum tunneling (MQT) theory, with a small correction due to residual noise in the bias current. In the two-level limit, where the SQUID constitutes a phase qubit, an observed contrast of 0.54 indicates a significant loss in contrast compared to the MQT prediction. It is attributed to spurious depolarization (loss of excited state occupancy) during the leading edge of the adiabatic flux measurement pulse. We give a simple phenomenological relaxation model which is able to predict the observed contrast of multilevel Rabi oscillations for various microwave amplitudes.
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页数：11
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