Remote Entanglement of Superconducting Qubits

Superconducting qubits are a leading platform for realizing quantum information processing devices. An open challenge for these systems is to entangle on demand two arbitrary superconducting qubits that are not nearest neighbors. A possible way to achieve this goal is to first entangle each stationary superconducting qubit with a travelling microwave coherent state. Then, performing joint measurements on these two coherent states leaves the two stationary qubits in an entangled state. Remarkably, this joint measurement operation can be readily accomplished using the process of phase-preserving amplification which can be implemented with superconducting Josephson parametric amplifiers. We present data on the experimental realization of this protocol using two superconducting qubits connected to a Josephson Parametric Convertor (JPC) operating as a nearly quantum-limited phase-preserving amplifier. We find that the fidelity of the final entangled state that we create is limited by the loss of information between the qubit and the amplifier. These losses are a consequence of the many auxiliary microwave components and interconnects in the qubit-amplifier system. As a means to mitigate these losses, we will present a new wireless architecture for these parametric amplifiers that eliminates many of these auxiliary components while simplifying their assembly and integration into current experiments.