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arXiv · 2202.04227

Feedback stabilization of the resonant frequency in tunable microwave cavities with single-photon occupancy

S. Kanhirathingal·B. Thyagarajan·B. L. Brock·Juliang Li·E. Jeffrey·M. P. Blencowe·J. Y. Mutus·A. J. Rimberg
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Abstract

We successfully demonstrate low-frequency noise suppression in the resonant frequency fluctuations of a cavity-embedded Cooper pair transistor (cCPT) driven at single-photon occupancy. In particular, we report a reduction in the resonant frequency fluctuations caused by the internal charge noise over a bandwidth of $\sim$1.4 kHz when the cavity is driven at an average photon number $n=10$, and a bandwidth of 11 Hz for average $n=1$. The gate-dependent tunability of the cCPT allows us to implement a feedback-scheme, derived from the Pound-Drever-Hall locking technique. This reduces fluctuations due to intrinsic charge-noise, which otherwise interferes with the cCPT's operation as a near quantum-limited electrometer. We believe our technique can be generalized to achieve frequency stabilization in tunable microwave resonators that play a vital role in today's quantum computing architecture, thereby moderating the limitations in detection caused by the intrinsic $1/f$-noise on such circuit devices. The work discusses the various aspects relating to the operation of a fully functional feedback loop down to the single-photon level.

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S. Kanhirathingal, B. Thyagarajan, B. L. Brock, Juliang Li, E. Jeffrey, M. P. Blencowe, J. Y. Mutus, A. J. Rimberg. 2022-02-09. Feedback stabilization of the resonant frequency in tunable microwave cavities with single-photon occupancy. https://arxiv.org/abs/2202.04227

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