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Cavity QED with superconducting qubits – a multi-pole approach


Superconducting Josephson-junction qubits are an emerging technology for quantum information processing. They offer a scalable, tunable, and coherent platform to study quantum systems. These qubits can be engineered with strong coupling to two or three-dimensional microwave cavities which implements the cavity QED paradigm – coherent coupling of a two-level system to a harmonic oscillator. Cavities enable high-fidelity qubit readout and a common “bus” for qubit-qubit interactions. In this talk, I will discuss our device at the University of Chicago which couples two superconducting transmon-type qubits using a planar multi-cavity (multi-pole) quantum filter. The multi-pole architecture allows for high contrast two-qubit gates; on-resonance the qubit-qubit interactions are strong, but off-resonance the interactions are exponentially suppressed in the number of filter poles. I will outline our adiabatic multi-pole (AMP) entangling gate protocol which we utilize to prepare a Bell state with > 90% fidelity in 100ns. The multi-pole architecture is a promising approach towards scalable multi-qubit circuits, lattice based quantum simulation, and photonic registers.