Quantum non-demolition measurement of a superconducting two-level system
Quantum non-demolition measurement of a superconducting two-level system
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DOI：
10.1038/nphys509
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发表时间：
2007-02-01
期刊：
影响因子：
19.6
通讯作者：
Mooij, J. E.
中科院分区：
文献类型：
--
作者：
Lupascu, A.;Saito, S.;Mooij, J. E.
在量子力学中，测量过程是信息提取和量子系统状态扰动之间的微妙相互作用。量子非破坏(QND)测量通过使用特定的系统-探测器相互作用来最大限度地减少这种干扰，该系统-探测器相互作用保留了量子系统中合适的算子的本征态。这导致了一种理想的投射测量。我们给出了两个连续测量量子二能级系统--超导磁通量子比特--的实验，通过探测耦合非线性谐振器的滞后行为。两个测量结果之间的大相关性表明了读出方法的QND性质。超导量子比特的QND测量是可能的，这一事实加强了这样一个概念，即这些制造出来的介观系统将被视为基本的量子对象。我们的结果也适用于状态准备和纠错等协议的量子信息处理。
In quantum mechanics, the process of measurement is a subtle interplay between extraction of information and disturbance of the state of the quantum system. A quantum non-demolition (QND) measurement minimizes this disturbance by using a particular system-detector interaction that preserves the eigenstates of a suitable operator of the quantum system. This leads to an ideal projective measurement. We present experiments in which we carry out two consecutive measurements on a quantum two-level system, a superconducting flux qubit, by probing the hysteretic behaviour of a coupled nonlinear resonator. The large correlation between the results of the two measurements demonstrates the QND nature of the readout method. The fact that a QND measurement is possible for superconducting qubits strengthens the notion that these fabricated mesoscopic systems are to be regarded as fundamental quantum objects. Our results are also relevant for quantum-information processing for protocols such as state preparation and error correction.