Measurement-based quantum control of mechanical motion
Measurement-based quantum control of mechanical motion
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DOI：
10.1038/s41586-018-0643-8
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发表时间：
2018-11-01
期刊：
影响因子：
64.8
通讯作者：
Schliesser, Albert
中科院分区：
文献类型：
--
作者：
Rossi, Massimiliano;Mason, David;Schliesser, Albert
通过观察量子系统的动力学来控制它是复杂的，因为测量过程的反向作用--也就是说，由于将系统耦合到测量仪器而导致的不可避免的量子干扰。一种有效的测量方法是最大限度地增加每个干扰所获得的信息量。然后，可以使用实时反馈来抵消测量的反向作用，并控制量子态的演变。这种基于测量的量子控制已经在腔和电路量子电动力学的干净环境中得到了证明，但它在运动自由度上的应用仍然难以捉摸。在这里，我们演示了毫米大小的薄膜谐振器运动的基于测量的量子控制。光学机械换能器在毫秒级相干时间的一小部分内解决了谐振器的零点运动，总体测量效率接近1。电子反馈回路将位置记录转换为使谐振器模式冷却到其量子基态(剩余热占有率约为0.29)的力。这个占有率比边带冷却的量子反作用极限低9分贝，比热环境的平衡占有率低6个数量级。因此，我们实现了该领域的一个长期目标，为基于测量的量子控制的自由度增加了位置和动量，在量子信息处理和引力波探测器方面具有潜在的应用。
Controlling a quantum system by using observations of its dynamics is complicated by the backaction of the measurement process-that is, the unavoidable quantum disturbance caused by coupling the system to a measurement apparatus. An efficient measurement is one that maximizes the amount of information gained per disturbance incurred. Real-time feedback can then be used to cancel the backaction of the measurement and to control the evolution of the quantum state. Such measurement-based quantum control has been demonstrated in the clean settings of cavity and circuit quantum electrodynamics, but its application to motional degrees of freedom has remained elusive. Here we demonstrate measurement-based quantum control of the motion of a millimetre-sized membrane resonator. An optomechanical transducer resolves the zero-point motion of the resonator in a fraction of its millisecond-scale coherence time, with an overall measurement efficiency close to unity. An electronic feedback loop converts this position record to a force that cools the resonator mode to its quantum ground state (residual thermal occupation of about 0.29). This occupation is nine decibels below the quantum-backaction limit of sideband cooling and six orders of magnitude below the equilibrium occupation of the thermal environment. We thus realize a long-standing goal in the field, adding position and momentum to the degrees of freedom that are amenable to measurement-based quantum control, with potential applications in quantum information processing and gravitational-wave detectors.