JILA, National Institute of Standards and Technology and the University of Colorado, Boulder, Colorado 80309, USA and Department of Physics, University of Colorado, Boulder, Colorado 80309, USA.
Phys Rev Lett. 2018 Jun 1;120(22):227701. doi: 10.1103/PhysRevLett.120.227701.
We demonstrate an acoustical analog of a circuit quantum electrodynamics system that leverages acoustic properties to enable strong multimode coupling in the dispersive regime while suppressing spontaneous emission to unconfined modes. Specifically, we fabricate and characterize a device that comprises a flux tunable transmon coupled to a 300 μm long surface acoustic wave resonator. For some modes, the qubit-cavity coupling reaches 6.5 MHz, exceeding the cavity loss rate (200 kHz), qubit linewidth (1.1 MHz), and the cavity free spectral range (4.8 MHz), placing the device in both the strong coupling and strong multimode regimes. With the qubit detuned from the confined modes of the cavity, we observe that the qubit linewidth strongly depends on its frequency, as expected for spontaneous emission of phonons, and we identify operating frequencies where this emission rate is suppressed.
我们展示了一种声学类比的电路量子电动力学系统，该系统利用声学性质在色散区域实现强多模耦合，同时抑制自发发射到非受限模式。具体来说，我们制造并表征了一种由通量可调谐的超导量子比特与 300μm 长的表面声波谐振器耦合而成的器件。对于某些模式，量子比特-腔耦合达到 6.5MHz，超过了腔损耗率（200kHz）、量子比特线宽（1.1MHz）和腔自由光谱范围（4.8MHz），使器件处于强耦合和强多模区域。当量子比特从腔的受限模式失谐时，我们观察到量子比特线宽强烈依赖于其频率，这是声子自发发射的预期结果，并且我们确定了在这些发射率被抑制的工作频率。
