Coupling Superconducting Qubits via a Cavity Bus

Abstract

Superconducting circuits are promising candidates for constructing quantum bits (qubits) in a quantum computer; single-qubit operations are now routine, and several examples of two qubit interactions and gates having been demonstrated. These experiments show that two nearby qubits can be readily coupled with local interactions. Performing gates between an arbitrary pair of distant qubits is highly desirable for any quantum computer architecture, but has not yet been demonstrated. An efficient way to achieve this goal is to couple the qubits to a quantum bus, which distributes quantum information among the qubits. Here we show the implementation of such a quantum bus, using microwave photons confined in a transmission line cavity, to couple two superconducting qubits on opposite sides of a chip. The interaction is mediated by the exchange of virtual rather than real photons, avoiding cavity induced loss. Using fast control of the qubits to switch the coupling effectively on and off, we demonstrate coherent transfer of quantum states between the qubits. The cavity is also used to perform multiplexed control and measurement of the qubit states. This approach can be expanded to more than two qubits, and is an attractive architecture for quantum information processing on a chip.

6 pages, 4 figures, to be published in Nature

References in corpus (7)

• Charge insensitive qubit design derived from the Cooper pair box
• Resolving photon number states in a superconducting circuit
• Quantum information processing with circuit quantum electrodynamics
• Approaching Unit Visibility for Control of a Superconducting Qubit with Dispersive Readout
• AC-Stark Shift and Dephasing of a Superconducting Qubit Strongly Coupled to a Cavity Field
• Generating Single Microwave Photons in a Circuit
• Spectroscopy on two coupled flux qubits

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