Venkatraman Jayameenakshi, Cortiñas Rodrigo G, Frattini Nicholas E, Xiao Xu, Devoret Michel H
Department of Applied Physics, Yale University, New Haven, CT 06520.
Department of Physics, Yale University, New Haven, CT 06520.
Proc Natl Acad Sci U S A. 2024 Jun 11;121(24):e2311241121. doi: 10.1073/pnas.2311241121. Epub 2024 Jun 5.
We present the experimental finding of multiple simultaneous two-fold degeneracies in the spectrum of a Kerr oscillator subjected to a squeezing drive. This squeezing drive resulting from a three-wave mixing process, in combination with the Kerr interaction, creates an effective static two-well potential in the phase space rotating at half the frequency of the sinusoidal drive generating the squeezing. Remarkably, these degeneracies can be turned on-and-off on demand, as well as their number by simply adjusting the frequency of the squeezing drive. We find that when the detuning Δ between the frequency of the oscillator and the second subharmonic of the drive equals an even multiple of the Kerr coefficient , [Formula: see text], the oscillator displays [Formula: see text] exact, parity-protected, spectral degeneracies, insensitive to the drive amplitude. These degeneracies can be explained by the unusual destructive interference of tunnel paths in the classically forbidden region of the double well static effective potential that models our experiment. Exploiting this interference, we measure a peaked enhancement of the incoherent well-switching lifetime, thus creating a protected cat qubit in the ground state manifold of our oscillator. Our results illustrate the relationship between degeneracies and noise protection in a driven quantum system.
我们展示了在受压缩驱动的克尔振荡器频谱中多个同时存在的双重简并的实验发现。这种由三波混频过程产生的压缩驱动，与克尔相互作用相结合，在以产生压缩的正弦驱动频率的一半旋转的相空间中创建了一个有效的静态双阱势。值得注意的是，这些简并可以按需开启和关闭，其数量也可以通过简单地调整压缩驱动的频率来改变。我们发现，当振荡器频率与驱动的第二个次谐波之间的失谐量Δ等于克尔系数的偶数倍，即[公式：见正文]时，振荡器会显示出[公式：见正文]个精确的、宇称保护的频谱简并，且对驱动幅度不敏感。这些简并可以通过在模拟我们实验的双阱静态有效势的经典禁戒区域中隧道路径的异常相消干涉来解释。利用这种干涉，我们测量到了非相干阱切换寿命的峰值增强，从而在我们振荡器的基态流形中创建了一个受保护的猫态量子比特。我们的结果说明了驱动量子系统中简并与噪声保护之间的关系。
