Resolving Phonon Fock States in a Multimode Cavity with a Double-Slit Qubit
Resolving Phonon Fock States in a Multimode Cavity with a Double-Slit Qubit
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DOI：
10.1103/physrevx.9.021056
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发表时间：
2019-06-20
影响因子：
12.5
通讯作者：
Lehnert, K. W.
中科院分区：
文献类型：
--
作者：
Sletten, L. R.;Moores, B. A.;Lehnert, K. W.
我们解析了与多模声腔耦合的超导量子位的频谱中的声子数状态。此分辨率的关键在于量子位-声子相互作用中的尖锐频率依赖性，该相互作用是通过将量子位与相隔大约 40 个声波波长的两个位置的表面声波耦合而设计的。与双缝衍射类似，由此产生的干扰在量子位-声子相互作用中产生高对比度频率结构。我们在多腔模式的耦合速率和无约束模式的量子位自发发射速率中观察到这种频率结构。我们使用这种尖锐的频率结构来解析单个声子，方法是将量子位调整到破坏性干扰的频率，其中所有声学相互作用都是色散的。通过激发几个失谐但强耦合的声子模式并测量所得的量子位光谱，我们观察到，对于两种模式，该设备进入强色散状态，其中单个声子被光谱解析。
We resolve phonon number states in the spectrum of a superconducting qubit coupled to a multimode acoustic cavity. Crucial to this resolution is the sharp frequency dependence in the qubit-phonon interaction engineered by coupling the qubit to surface acoustic waves in two locations separated by similar to 40 acoustic wavelengths. In analogy to double-slit diffraction, the resulting interference generates high-contrast frequency structure in the qubit-phonon interaction. We observe this frequency structure both in the coupling rate to multiple cavity modes and in the qubit spontaneous emission rate into unconfined modes. We use this sharp frequency structure to resolve single phonons by tuning the qubit to a frequency of destructive interference where all acoustic interactions are dispersive. By exciting several detuned yet strongly coupled phononic modes and measuring the resulting qubit spectrum, we observe that, for two modes, the device enters the strong dispersive regime where single phonons are spectrally resolved.