Realizing all-to-all couplings among detachable quantum modules using a microwave quantum state router

TL;DR

This paper introduces a microwave quantum state router that enables all-to-all couplings among four detachable quantum modules, facilitating scalable and flexible quantum networks with high fidelity and coherence.

Contribution

It presents a novel router architecture based on Josephson junctions for modular quantum computing, demonstrating coherent exchange, entanglement, and parallel operations among modules.

Findings

Achieved average full-iSWAP time of 764ns.

Inferred inter-module exchange fidelity of 0.969.

Demonstrated photon transfer and entanglement between modules.

Abstract

One of the primary challenges in realizing large-scale quantum processors is the realization of qubit couplings that balance interaction strength, connectivity, and mode confinement. Moreover, it is very desirable for the device elements to be detachable, allowing components to be built, tested, and replaced independently. In this work, we present a microwave quantum state router, centered on parametrically driven, Josephson-junction based three-wave mixing, that realizes all-to-all couplings among four detachable quantum modules. We demonstrate coherent exchange among all four communication modes, with an average full-iSWAP time of 764ns and average inferred inter-module exchange fidelity of 0.969, limited by mode coherence. We also demonstrate photon transfer and pairwise entanglement between module qubits, and parallel operation of simultaneous iSWAP exchange across the router. Our router-module architecture serves as a prototype of modular quantum computer that has great potential for enabling flexible, demountable, large-scale quantum networks of superconducting qubits and cavities.