Strong magnetic coupling of an ultracold gas to a superconducting waveguide cavity

TL;DR

This paper demonstrates strong magnetic coupling between an ultracold atomic ensemble and a superconducting microwave cavity, enabling advanced quantum hybrid systems with potential applications in quantum information and control.

Contribution

It introduces a hybrid quantum device integrating ultracold atoms with a superconducting resonator, achieving strong coupling for the first time in this configuration.

Findings

Achieved effective coupling rate of ~40 kHz exceeding cavity linewidth of ~7 kHz.

Demonstrated potential for quantum information transfer between atomic and solid-state systems.

Outlined applications including quantum interconnects, microwave super-radiance, and resonator cooling.

Abstract

Placing an ensemble of $10^6$ ultracold atoms in the near field of a superconducting coplanar waveguide resonator (CPWR) with $Q \sim 10^6$ one can achieve strong coupling between a single microwave photon in the CPWR and a collective hyperfine qubit state in the ensemble with $g_\textit{eff} / {2 \pi} \sim 40$ kHz larger than the cavity line width of ${\kappa}/{2 \pi} \sim 7$ kHz. Integrated on an atomchip such a system constitutes a hybrid quantum device, which also can be used to interconnect solid-state and atomic qubits, to study and control atomic motion via the microwave field, observe microwave super-radiance, build an integrated micro maser or even cool the resonator field via the atoms.