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Single-shot measurement of the Josephson charge qubit

O. Astafiev·Yu. A. Pashkin·T. Yamamoto·Y. Nakamura·J. S. Tsai
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Abstract

We demonstrate single-shot readout of quantum states of the Josephson charge qubit. The quantum bits are transformed into and stored as classical bits (charge quanta) in a dynamic memory cell - a superconducting island. The transformation of state |1> (differing form state |0> by an extra Cooper pair) is a result of a controllable quasiparticle tunneling to the island. The charge is then detected by a conventional single-electron transistor, electrostatically decoupled from the qubit. We study relaxation dynamics in the system and obtain the readout efficiency of 87% and 93% for |1> and |0> states, respectively.

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O. Astafiev, Yu. A. Pashkin, T. Yamamoto, Y. Nakamura, J. S. Tsai. 2004-02-25. Single-shot measurement of the Josephson charge qubit. https://doi.org/10.1103/physrevb.69.180507

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