Gradual partial-collapse theory for ideal nondemolition longitudinal readout of qubits in circuit QED
Gradual partial-collapse theory for ideal nondemolition longitudinal readout of qubits in circuit QED
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电路 QED 中量子位理想非破坏纵向读出的渐进部分崩溃理论
DOI：
10.1103/physreva.98.022121
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发表时间：
2017-08
影响因子：
2.9
通讯作者：
Li Xin Qi
中科院分区：
文献类型：
--
作者：
Feng Wei;Zhang Cheng;Wang Zhong;Qin Lupei;Li Xin Qi
在电路QED中，传统的量子位测量方法是利用量子位-腔耦合的色散机制，这导致了量子非破坏（QND）读出的近似方案。由于所谓的珀塞尔效应，该方案在强耦合和/或强测量驱动的情况下变得有问题。最近的一个建议，凭借纵向耦合提出了一个新的方案，实现快速，高保真，和理想的量子位态的QND读出。目前的工作的目的是双重的：（i）在平行的色散读出在过去的几年中所做的，我们进行了这个最近的计划，在量子轨迹方程和量子贝叶斯方法的逐步部分坍缩理论。部分坍缩弱测量理论在基于测量的反馈控制等量子应用中具有重要的应用价值。(ii)在物理方面，我们构造了连续测量条件下的量子比特-腔联合纠缠态，并对量子效率、量子比特态纯度和输出电流的信噪比进行了综合分析。联合态和量子贝叶斯规则的结合提供了一种与纵向耦合相关联的腔重置的一般方案，它可以将量子比特从与腔态的纠缠中恢复到量子纯态，从而有利于量子比特旋转后的后续部分坍缩测量。
The conventional method of qubit measurements in circuit QED is employing the dispersive regime of qubit-cavity coupling, which results in an approximated scheme of quantum nondemolition (QND) readout. This scheme becomes problematic in the case of strong coupling and/or strong measurement drive, owing to the so-called Purcell effect. A recent proposal by virtue of longitudinal coupling suggests a new scheme to realize fast, high-fidelity, and ideal QND readout of qubit state. The aim of the present work is twofold: (i) In parallel to what has been done in the past years for the dispersive readout, we carry out the gradual partial-collapse theory for this recent scheme, in terms of both the quantum trajectory equation and quantum Bayesian approaches. The partial-collapse weak measurement theory is useful for such as the measurement-based feedback control and other quantum applications. (ii) In the physical aspect, we construct the joint qubit-plus-cavity entangled state under continuous measurement and present a comprehensive analysis for the quantum efficiency, qubit-state purity, and signal-to-noise ratio in the output currents. The combination of the joint state and the quantum Bayesian rule provides a generalized scheme of cavity reset associated with the longitudinal coupling, which can restore the qubit to a quantum pure state from entanglement with the cavity states, and thus benefits the successive partial-collapse measurements after qubit rotations.
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影响因子：
2
作者：
P. Knight
通讯作者：
P. Knight
DOI：
--
发表时间：
--
期刊：
--
影响因子：
--
作者：
A. Wallraff;D. Schuster;A. Blais;L. Frunzio;R.-S. Huang;J. Majer;S. Kumar;S. Girvin;R. Schoelkopf
通讯作者：
A. Wallraff;D. Schuster;A. Blais;L. Frunzio;R.-S. Huang;J. Majer;S. Kumar;S. Girvin;R. Schoelkopf
影响因子：
8.6
作者：
Didier, Nicolas;Bourassa, Jerome;Blais, Alexandre
通讯作者：
Blais, Alexandre
影响因子：
8.6
作者：
Gammelmark, Soren;Julsgaard, Brian;Molmer, Klaus
通讯作者：
Molmer, Klaus
影响因子：
19.6
作者：
Lupascu, A.;Saito, S.;Mooij, J. E.
通讯作者：
Mooij, J. E.