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

• Published in: npj quantum information Vol. 9; no. 1; pp. 54 - 9
• Main Authors: Zhou, Chao, Lu, Pinlei, Praquin, Matthieu, Chien, Tzu-Chiao, Kaufman, Ryan, Cao, Xi, Xia, Mingkang, Mong, Roger S. K., Pfaff, Wolfgang, Pekker, David, Hatridge, Michael
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 06.06.2023; Nature Publishing Group; Nature Portfolio
• Subjects: 639/766/483/2802; 639/766/483/481; Circuits; Classical and Quantum Gravitation; Communication channels; Design; Physics; Physics and Astronomy; Quantum Computing; Quantum Field Theories; Quantum Information Technology; Quantum Physics; Relativity Theory; Spintronics; String Theory
• ISSN: 2056-6387; 2056-6387
• DOI: 10.1038/s41534-023-00723-7

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- i SWAP time of 764 ns 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 i SWAP 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.