Quantum Efficiency of Charge Qubit Measurements Using a Single Electron Transistor |
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Authors: | Yin Ye Jing Ping HuJun Jiao Shu-Shen Li Xin-Qi Li |
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Institution: | 1. State Key Laboratory for Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing, 100083, China 2. Department of Physics, Shanxi University, Taiyuan, 030006, China 3. Department of Physics, Beijing Normal University, Beijing, 100875, China
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Abstract: | The quantum efficiency, which characterizes the quality of information gain against information loss, is an important figure
of merit for any realistic quantum detectors in the gradual process of collapsing the state being measured. In this work we consider the problem of solid-state charge qubit measurements
with a single-electron-transistor (SET). We analyze two models: one corresponds to a strong response SET, and the other is
a tunable one in response strength. We find that the response strength would essentially bound the quantum efficiency, making
the detector non-quantum-limited. Quantum limited measurements, however, can be achieved in the limits of strong response
and asymmetric tunneling. The present study is also associated with appropriate justifications for the measurement and backaction-dephasing
rates, which were usually evaluated in controversial methods. |
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