Towards highly efficient broadband superconducting quantum memory

TL;DR

This paper presents a highly efficient broadband multimode superconducting quantum memory capable of storing multiple microwave spectral modes with high efficiency and low noise, advancing quantum computing capabilities.

Contribution

It introduces an on-chip multimode quantum memory with significantly improved efficiency over previous designs, enabling practical superconducting quantum circuits.

Findings

Achieved up to 60% efficiency at single photon level

Demonstrated multimode storage with over 73% efficiency at higher intensities

Confirmed noiseless storage via quantum process tomography

Abstract

Microwave quantum memory promises advanced capabilities for noisy intermediate-scale superconducting quantum computers. Existing approaches to microwave quantum memory lack complete combination of high efficiency, long storage time, noiselessness and multi-qubit capacity. Here we report an efficient microwave broadband multimode quantum memory. The memory stores two spectral modes of single photon level microwave radiation in on-chip system of eight coplanar superconducting resonators. Single mode storage shows a power efficiency of up to $60\pm 3\%$ at single photon energy and more than $73\pm 3\%$ at higher intensity. The demonstrated efficiency is an order of magnitude larger than the previously reported multimode microwave quantum memory. The noiseless character of the storage is confirmed by coherent state quantum process tomography. The demonstrated results pave the way to further increase in efficiency and hence building a practical multimode microwave memory for superconducting quantum circuits.