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Resonant Cooper Pair Tunneling: Quantum Noise and Measurement Characteristics

A. A. Clerk·S. M. Girvin·A. K. Nguyen·A. D. Stone
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Abstract

We study the quantum charge noise and measurement properties of the double Cooper pair resonance point in a superconducting single-electron transistor (SSET) coupled to a Josephson charge qubit. Using a density matrix approach for the coupled system, we obtain a full description of the measurement back-action; for weak coupling, this is used to extract the quantum charge noise. Unlike the case of a non-superconducting SET, the back-action here can induce population inversion in the qubit. We find that the Cooper pair resonance process allows for a much better measurement than a similar non-superconducting SET, and can approach the quantum limit of efficiency.

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A. A. Clerk, S. M. Girvin, A. K. Nguyen, A. D. Stone. 2002-03-27. Resonant Cooper Pair Tunneling: Quantum Noise and Measurement Characteristics. https://doi.org/10.1103/physrevlett.89.176804

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