Microwave Quantum Link between Superconducting Circuits Housed in Spatially Separated Cryogenic Systems

TL;DR

This paper demonstrates a cryogenic microwave link connecting superconducting qubits in separate cryogenic systems over five meters, enabling state transfer and entanglement with high fidelity, advancing quantum networking capabilities.

Contribution

It reports the first successful coherent microwave link between superconducting circuits in separate cryogenic environments over meters, enabling quantum state transfer and entanglement.

Findings

Achieved 85.8% average transfer fidelity.

Generated entanglement with 79.5% fidelity.

Demonstrated scalable cryogenic quantum networking.

Abstract

Superconducting circuits are a strong contender for realizing quantum computing systems, and are also successfully used to study quantum optics and hybrid quantum systems. However, their cryogenic operation temperatures and the current lack of coherence-preserving microwave-to-optical conversion solutions have hindered the realization of superconducting quantum networks either spanning different cryogenics systems or larger distances. Here, we report the successful operation of a cryogenic waveguide coherently linking transmon qubits located in two dilution refrigerators separated by a physical distance of five meters. We transfer qubit states and generate entanglement on-demand with average transfer and target state fidelities of 85.8 % and 79.5 %, respectively, between the two nodes of this elementary network. Cryogenic microwave links do provide an opportunity to scale up systems for quantum computing and create local area quantum communication networks over length scales of at least tens of meters.