JunYan Luo, Lun-Wu Zhu, Xiao-Ling He, Bensheng Yun, Shiping Ruan
Continuous measurement of a quantum two-level system (qubit) by mesoscopic charge detectors has attracted wide attention in the community of solid-state quantum computation. In this work, we revisit the measurement of a charge qubit by a quantum point contact, with particular attention paid to the unique non-Markovian measurement characteristics. The finite-frequency-support feature due to non-Markovian correlation leads to a remarkable suppression of the pedestal in noise spectrum, which results in a drastic violation of the Korotkov-Averin bound, the upper limit of the singleto-noise ratio imposed quantum mechanically on linear detectors. For a large measurement voltage and bandwidth, the non-Markovian effect gives rise to a complete inhibition of coherent jumps (quantum Zeno effect), as identified by the telegraph noise peaks in the spectrum.
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http://arxiv.org/abs/1203.2233
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