利用弱耦合量子点接触获得电荷量子比特的态信息
The information about the state of a charge qubit gained by a weakly coupled quantum point contact
摘要：
我们分析的信息，人们可以了解一个量子二能级系统的状态，即量子位，当探测附近的检测器弱。我们考虑一般情况下，量子比特的哈密顿量和量子比特的运营商探测的检测器不对易。由于量子比特的状态在被探测时不断演变，并且测量数据与探测器相关的背景噪声混合，因此在这种情况下，人们可能会期望探测器失败。然而，我们表明，在适当的条件下，并通过适当的分析测量数据的有用信息的初始状态的量子比特可以提取。我们的方法补充了通常的主方程和量子轨道方法，其描述了测量过程中量子位的量子态的演化，但不跟踪所获得的测量信息。
英文摘要：
We analyze the information that one can learn about the state of a quantum two-level system, i.e. a qubit, when probed weakly by a nearby detector. We consider the general case where the qubit Hamiltonian and the qubit's operator probed by the detector do not commute. Because the qubit's state keeps evolving while being probed and the measurement data is mixed with a detector-related background noise, one might expect the detector to fail in this case. We show, however, that under suitable conditions and by proper analysis of the measurement data useful information about the initial state of the qubit can be extracted. Our approach complements the usual master-equation and quantum-trajectory approaches, which describe the evolution of the qubit's quantum state during the measurement process but do not keep track of the acquired measurement information.
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