Coherent-State Storage and Retrieval Between Superconducting Cavities Using Parametric Frequency Conversion

TL;DR

This paper demonstrates a method for storing and retrieving quantum information in superconducting cavities using a flux-driven Josephson junction to controllably swap coherent states between modes, enabling fast read/write operations.

Contribution

It introduces a dual cavity architecture with tunable coupling via parametric frequency conversion for efficient quantum state storage and retrieval.

Findings

Achieved controllable swapping of coherent states between cavities.

Demonstrated full control over coupling rates between modes.

Enabled fast, sequenced quantum state storage and retrieval.

Abstract

In superconducting quantum information, machined aluminum superconducting cavities have proven to be a well-controlled, low-dissipation electromagnetic environment for quantum circuits such as qubits. They can possess large internal quality factors, $Q_{int}>10^8$, and present the possibility of storing quantum information for times far exceeding those of microfabricated circuits. However, in order to be useful as a storage element, these cavities require a fast "read/write" mechanism--- in other words, they require tunable coupling between other systems of interest such as other cavity modes and qubits, as well as any associated readout hardware. In this work, we demonstrate these qualities in a simple dual cavity architecture in which a low-Q "readout" mode is parametrically coupled to a high-Q "storage" mode, allowing us to store and retrieve classical information. Specifically, we employ a flux-driven Josephson junction-based coupling scheme to controllably swap coherent states between two cavities, demonstrating full, sequenced control over the coupling rates between modes.