Resolving the energy levels of a nanomechanical oscillator
Resolving the energy levels of a nanomechanical oscillator
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DOI：
10.1038/s41586-019-1386-x
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发表时间：
2019-07-25
期刊：
影响因子：
64.8
通讯作者：
Safavi-Naeini, Amir H.
中科院分区：
文献类型：
--
作者：
Arrangoiz-Arriola, Patricio;Wollack, E. Alex;Safavi-Naeini, Amir H.
摆动的机械物体的量子本质绝非显而易见。描述机械振子经典运动的相干态没有明确定义的能量，而是等间距能量本征态的量子叠加。只有用测量能量的精度大于单个声子能量的仪器，才有可能揭示这种量子化的结构。实现这种灵敏度的一种方法是在振子和原子之间设计一种强烈但非共振的相互作用。在具有足够量子相干性的系统中，这种相互作用允许人们使用原子跃迁频率中可分辨的差异来区分不同的能量本征态。对于光子，已经在腔(1，2)和电路量子电动力学(3)中进行了这样的色散测量。在这里，我们报道了一个实验，在这个实验中，一个人造原子以足够的灵敏度感知一个被驱动的纳米机械振子的运动能量，以解决其能量的量子化。为了实现这一点，我们构建了一个混合平台，将纳米机械压电谐振器和微波超导量子比特集成在同一芯片上。我们用共振脉冲激发声子，并探测量子比特的激发谱，观察到声子数相关的频移，这些频移大约是量子比特线宽的五倍。我们的结果展示了一个完全集成的量子声学平台，它结合了大耦合、可观的相干时间和对机械模式结构的出色控制。通过适度的实验改进，我们预计我们的方法将能够实现对声子的量子非破坏测量(4)，并将导致使用芯片级纳米机械设备的量子传感器和信息处理方法(5)。
The quantum nature of an oscillating mechanical object is anything but apparent. The coherent states that describe the classical motion of a mechanical oscillator do not have a well defined energy, but are quantum superpositions of equally spaced energy eigenstates. Revealing this quantized structure is only possible with an apparatus that measures energy with a precision greater than the energy of a single phonon. One way to achieve this sensitivity is by engineering a strong but nonresonant interaction between the oscillator and an atom. In a system with sufficient quantum coherence, this interaction allows one to distinguish different energy eigenstates using resolvable differences in the atom's transition frequency. For photons, such dispersive measurements have been performed in cavity(1,2) and circuit quantum electrodynamics(3). Here we report an experiment in which an artificial atom senses the motional energy of a driven nanomechanical oscillator with sufficient sensitivity to resolve the quantization of its energy. To realize this, we build a hybrid platform that integrates nanomechanical piezoelectric resonators with a microwave superconducting qubit on the same chip. We excite phonons with resonant pulses and probe the resulting excitation spectrum of the qubit to observe phonon-number-dependent frequency shifts that are about five times larger than the qubit linewidth. Our result demonstrates a fully integrated platform for quantum acoustics that combines large couplings, considerable coherence times and excellent control over the mechanical mode structure. With modest experimental improvements, we expect that our approach will enable quantum nondemolition measurements of phonons(4) and will lead to quantum sensors and information-processing approaches(5) that use chip-scale nanomechanical devices.