We propose a hybrid quantum gate between an atom and a microwave photon in a superconducting coplanar waveguide cavity by exploiting the strong resonant microwave coupling between adjacent Rydberg states. Using experimentally achievable parameters gate fidelities >0.99 are possible on submicrosecond time scales for waveguide temperatures below 40 mK. This provides a mechanism for generating entanglement between two disparate quantum systems and represents an important step in the creation of a hybrid quantum interface applicable for both quantum simulation and quantum information processing

We propose a method for reducing the sensitivity of atomic ground to Rydberg transitions to stray dc electric fields, using microwave-induced dressing of Rydberg states. Calculations are presented for the Cs 90S 1/2 and 90P 3/2 states. With zero dc bias electric field, a two-frequency ac field is used to simultaneously reduce the sensitivity of both states to dc field variations. The sensitivity reduction is a factor of 95 for the 90S 1/2 state and a factor of 1600 for the 90P 3/2 , mJ = 3/2 state. We also show how the two-frequency ac field can be used to cancel both second-and fourth-order terms in the polarizability of a single Rydberg state. These results are relevant to improving the stability of experiments that seek to excite Rydberg atoms in the proximity of charged surfaces.

We describe the design and characterization of superconducting coplanar waveguide cavities tailored to facilitate strong coupling between superconducting quantum circuits and single trapped Rydberg atoms. For initial superconductor-atom experiments at 4.2 K, we show that resonator quality factors above 10 4 can be readily achieved. Furthermore, we demonstrate that the incorporation of thick-film copper electrodes at a voltage antinode of the resonator provides a route to enhance the zero-point electric fields of the resonator in a trapping region that is 40 µm above the chip surface, thereby minimizing chip heating from scattered trap light. The combination of high resonator quality factor and strong electric dipole coupling between the resonator and the atom should make it possible to achieve the strong coupling limit of cavity quantum electrodynamics with this system. PACS numbers: 85.25.Am, 74.40.Gh Quantum computers will enable efficient solution of problems that are intractable on conventional, classical computers. A number of candidate physical systems for quantum bits ("qubits") are currently under investigation, including superconducting integrated circuits incorporating Josephson junctions 1-3 , semiconducting quantum dots 4-6 , trapped neutral atoms 7-9 , and trapped ions 10,11 . The various approaches each have strengths and weaknesses, and there are unsolved scientific challenges associated with scaling any of the current technologies. Against this backdrop, there has been a growing interest in the last several years in hybrid approaches to quantum information processing that combine the best features of several different methods [12][13][14][15][16][17][18][19][20] . Recent efforts to interface disparate quantum systems include coupling superconducting resonators to quantum dots 21 , electronic spin ensembles 22 , and neutral atom clouds 23 .One attractive hybrid approach would involve a fast, high-fidelity superconducting quantum processor coupled to a stable, long-lived neutral atom quantum memory via a Rydberg state. Superconductor gate times are of order 10 ns, and fidelities are now at the threshold for fault-tolerance in the surface code 24 ; however, coherence times are typically tens of µs. In contrast, neutral atoms offer coherence times of order seconds, so that the superconductor-atom system would yield an unprecedented ratio of coherence time to gate time. Moreover, a superconductor-atom quantum interface could open the door to efficient microwave-to-optical photon conversion, an essential ingredient in a distributed quantum information processing network 25,26 .The key technological obstacle to realization of a hybrid superconductor-atom system is the microwave a) mabeck2@wisc.edu b) Current address: Department of Physics, University Of Strathclyde, 107 Rottenrow East, Glasgow, United Kingdom photon-atom interface. Prior attempts to combine trapped neutral atoms with thin-film superconducting cavities have relied on magnetic coupling 13,15,18 ; due to the smallness of the magnetic momen...

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We briefly review the development history of the Gemini Planet Imager's 4K Boston Micromachines MEMS deformable mirror. We discuss essential calibration steps and algorithms to control the MEMS with nanometer precision, including voltage-phase calibration and influence function characterization. We discuss the integration of the MEMS into GPI's Adaptive Optics system at Lawrence Livermore and present experimental results of 1.5 kHz closed-loop control. We detail mitigation strategies in the coronagraph to reduce the impact of abnormal actuators on final image contrast.