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Single-shot measurement of the Josephson charge qubit

Research output: Contribution to journalJournal articlepeer-review

  • Oleg V. Astafiev
  • Yuri Pashkin
  • T. Yamamoto
  • Y. Nakamura
  • Jaw-Shen Tsai
Article number180507
<mark>Journal publication date</mark>1/05/2004
<mark>Journal</mark>Physical review B
Issue number18
Number of pages4
Publication StatusPublished
<mark>Original language</mark>English


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 u1& ~differing form state u0& 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 u1& and u0& states, respectively.