Dartmouth Events

Abstract: We report on recent experiments studying the cavity-embedded Cooper pair transistor (cCPT), a device which behaves as a nonlinear charge- and flux-tunable microwave cavity.  These experiments culminate in a demonstration of ultrasensitive electrometry using 16 attowatts of power, corresponding to the single-photon level of the cavity.  We measure a dispersive charge sensitivity of 14 ue/root(Hz), which is comparable to that of rf-SETs while using about 5 orders of magnitude less power.  This low-power operation enables the cCPT to be integrated with near quantum-limited amplifiers and could help facilitate the multiplexed readout of quantum-dot-based qubits.  Furthermore, our results support the feasibility of using the cCPT to mediate an optomechanical interaction that reaches the single-photon strong coupling regime.  Underpinning this charge sensitivity measurement is a detailed characterization of the device, with a particular emphasis on the effects of 1/f charge and flux noise.