A quantum memory with near-millisecond coherence in circuit QED

TL;DR

This paper presents a superconducting microwave cavity architecture that achieves near-millisecond quantum state coherence, significantly advancing quantum memory capabilities in circuit QED systems for quantum computing.

Contribution

The authors introduce a novel cavity design that enhances coherence times and enables rapid control and readout, improving quantum memory performance in superconducting circuits.

Findings

Achieved near-millisecond coherence times in a superconducting resonator.

Demonstrated strong coupling enabling MHz control and readout.

Improved coherence by nearly an order of magnitude over existing qubits.

Abstract

Significant advances in coherence have made superconducting quantum circuits a viable platform for fault-tolerant quantum computing. To further extend capabilities, highly coherent quantum systems could act as quantum memories for these circuits. A useful quantum memory must be rapidly addressable by qubits, while maintaining superior coherence. We demonstrate a novel superconducting microwave cavity architecture that is highly robust against major sources of loss that are encountered in the engineering of circuit QED systems. The architecture allows for near-millisecond storage of quantum states in a resonator while strong coupling between the resonator and a transmon qubit enables control, encoding, and readout at MHz rates. The observed coherence times constitute an improvement of almost an order of magnitude over those of the best available superconducting qubits. Our design is an ideal platform for studying coherent quantum optics and marks an important step towards hardware-efficient quantum computing with Josephson junction-based quantum circuits.