We have embedded a voltage-biased Cooper-pair transistor (CPT) in a high-Q superconducting microwave cavity. When the energy given to a tunneling Cooper pair by the voltage bias is equal to a multiple of the cavity photon frequency, the cavity is pumped to a strongly nonequilibrium state. The cavity photons act back on the CPT, allowing us to enter a regime of strongly correlated electronic-photonic transport. We directly observe the effects of photonic backaction on Cooper-pair transport, and see clear evidence for single-emitter lasing in the form of emission dominated by stimulated transport processes.

We report a technique for applying a dc voltage or current bias to the center conductor of a high-quality factor superconducting microwave cavity without significantly disturbing selected cavity modes. This is accomplished by incorporating dc bias lines into the cavity at specific locations. The measured S-matrix parameters of the system are in good agreement with theoretical predictions and simulations. We find that at 4 K the quality factor of the cavity degrades by less than 1% under the application of a dc bias.

We report a robust process for fabrication of surface-gated Si/SiGe quantum dots (QDs) with an integrated superconducting single-electron transistor (S-SET) charge sensor. A combination of a deep mesa etch and AlOx backfill is used to reduce gate leakage. After the leakage current is suppressed, Coulomb oscillations of the QD and the current-voltage characteristics of the S-SET are observed at a temperature of 0.3 K. Coupling of the S-SET to the QD is confirmed by using the S-SET to perform sensing of the QD charge state.

Submitted for the MAR10 Meeting of The American Physical Society Introduction of a DC Bias into a High-Q Microwave Cavity1 WEIWEI XUE, FEI CHEN, IAN HAYES, M.P. BLENCOWE, A.J. RIMBERG — The circuit quantum electrodynamics (QED) architecture has been demonstrated to allow study cavity QED physics in a high-Q onchip microwave cavity[1]. Here we develop a technique to apply a DC current or voltage bias to nanostructures embedded in the microwave cavity without significantly disturbing the cavity modes or degrading the Q at high frequencies. The DC biasing scheme will be discussed. Experimental results show good agreement with theoretical predictions. New highly nonlinear fully quantum mechanical devices can be developed by embedding Josephson junction devices such as Superconducting Quantum Interference Devices (SQUIDs) or single electron transistors (SETs) in the high-Q microwave cavity. Furthermore, by integrating a nanomechanical resonator, such cavities may also be used to investigate the quantum to classical transition. [1] A. Wallraff et al, Nature, 431, 162 (2004). 1This work is supported by the NSF under Grants Nos. DMR-0804488 and DMR0804477 and by the ARO under Agreement No. W911NF-06-1-0312.