Resonant cooper-pair tunneling: quantum noise and measurement characteristics.
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 backaction; for weak coupling, this is used to extract the quantum charge noise. Unlike the case of a nonsuperconducting SET, the backaction 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 nonsuperconducting SET, and can approach the quantum limit of efficiency.
Clerk
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AA
Department of Applied Physics and Physics, Yale University, New Haven, Connecticut, 06511, USA.
Girvin
S M
SM
Nguyen
A K
AK
Stone
A D
AD