Seamless high-Q microwave cavities for multimode circuit QED

TL;DR

This paper presents a novel seamless 3D microwave cavity with high photon lifetimes and strong multimode interactions, enabling advanced quantum control and paving the way for efficient quantum memories and many-body physics exploration.

Contribution

Introduction of a straightforward flute method for fabricating low-loss, multimode superconducting microwave cavities with high coherence and controllable mode spectra.

Findings

Single photon lifetimes of 2 ms across 9 modes

Cooperativities of 0.5-1.5×10^9 across modes

Universal single-mode quantum control with a single drive line

Abstract

Multimode cavity quantum electrodynamics ---where a two-level system interacts simultaneously with many cavity modes---provides a versatile framework for quantum information processing and quantum optics. Due to the combination of long coherence times and large interaction strengths, one of the leading experimental platforms for cavity QED involves coupling a superconducting circuit to a 3D microwave cavity. In this work, we realize a 3D multimode circuit QED system with single photon lifetimes of $2$ ms and cooperativities of $0.5-1.5\times10^9$ across 9 modes of a novel seamless cavity. We demonstrate a variety of protocols for universal single-mode quantum control applicable across all cavity modes, using only a single drive line. We achieve this by developing a straightforward flute method for creating monolithic superconducting microwave cavities that reduces loss while simultaneously allowing control of the mode spectrum and mode-qubit interaction. We highlight the flexibility and ease of implementation of this technique by using it to fabricate a variety of 3D cavity geometries, providing a template for engineering multimode quantum systems with exceptionally low dissipation. This work is an important step towards realizing hardware efficient random access quantum memories and processors, and for exploring quantum many-body physics with photons.