Recent experimental progresses with superconducting quantum networks

Superconducting quantum circuits show great promise for building scalable quantum processors. The size of superconducting quantum processors has steadily increased from a handful to dozens of qubits over the past decade, and will likely extend to thousands of qubits over the next decade with continuous efforts in qubit integration and packaging. However, problems such as available wafer area, device yield and control wiring fanout pose serious challenges as the chip size gets bigger and bigger. A modular approach, where smaller size quantum modules are individually constructed and calibrated, then assembled into a larger architecture using quantum coherent interconnects, can circumvent these challenges and scale up superconducting quantum computers in an additive manner. In recent years, several experiments have demonstrated the deterministic quantum state transfer between two superconducting quantum modules connected by coaxial cables or waveguides[1-5], with fidelities ranging from ~70% to ~80%. More recent efforts using direct wirebond connection[6] or capacitive coupling[7] between the quantum modules and a coaxial cable have significantly reduced the loss, improving the state transfer fidelity to ~90%.  In this talk, I will present our recent experimental progresses in this direction.

[1] Kurpiers, P. et al. Nature 558, 264–267 (2018).

[2] Axline, C. J. et al. Nat. Phys. 14, 705–710 (2018).

[3] Campagne-Ibarcq, P. et al. Phys. Rev. Lett. 120, 200501 (2018).

[4] Leung, N. et al., npj Quantum Inf. 5, 18 (2019).

[5] Magnard, P. et al., Phys. Rev. Lett. 125, 260502 (2020).

[6] Zhong, Y. et al., Nature 590, 571–575 (2021).

[7] Burkhart, L. D. et al., PRX Quantum 2, 030321 (2021).