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One-shot quantum measurement using a hysteretic DC-SQUID

O. Buisson, F. Balestro, J. P. Pekola, F. W. J. Hekking

cond-mat.supr-conarXiv:cond-mat/0308560

Abstract

We propose a single shot quantum measurement to determine the state of a Josephson charge quantum bit (qubit). The qubit is a Cooper pair box (CPB) and the measuring device is a two junction superconducting quantum interference device (dc-SQUID). This coupled system exhibits a close analogy with a Rydberg atom in a high Q cavity, except that in the present device we benefit from the additional feature of escape from the supercurrent state by macroscopic quantum tunneling, which provides the final read-out. We test the feasibility of our idea against realistic experimental circuit parameters and by analyzing the phase fluctuations of the qubit.

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