A hybrid quantum circuit consisting of a superconducting flux qubit coupled to both a spin ensemble and a transmission-line resonator

TL;DR

This paper proposes a hybrid quantum circuit using a superconducting flux qubit to enable strong coupling between a spin ensemble and a transmission-line resonator, facilitating quantum information transfer with fewer spins and potential for long-term quantum memory.

Contribution

It introduces a novel hybrid quantum circuit design that significantly reduces the number of spins needed for strong coupling, enhancing quantum memory and nonlinear effect exploration.

Findings

Achieves strong coupling with three to four orders fewer spins

Enables quantum information transfer between spin ensemble and resonator

Potential for long-time quantum memory and nonlinear effects exploration

Abstract

We propose an experimentally realizable hybrid quantum circuit for achieving a strong coupling between a spin ensemble and a transmission-line resonator via a superconducting flux qubit used as a data bus. The resulting coupling can be used to transfer quantum information between the spin ensemble and the resonator. In particular, in contrast to the direct coupling without a data bus, our approach requires far less spins to achieve a strong coupling between the spin ensemble and the resonator (e.g., three to four orders of magnitude less). This proposed hybrid quantum circuit could enable a long-time quantum memory when storing information in the spin ensemble, and allows the possibility to explore nonlinear effects in the ultrastrong-coupling regime.