High-performance quantum interconnect between bosonic modules beyond transmission loss constraints

TL;DR

This paper demonstrates a high-fidelity, low-loss quantum interconnect between superconducting modules using an aluminum coaxial cable, surpassing traditional transmission loss limits and enabling scalable distributed quantum computing.

Contribution

The work introduces a novel low-loss interconnect with high quality factor and high-fidelity state transfer, shifting performance constraints from transmission loss to interface effects.

Findings

Achieved a bus mode quality factor of 1.7 million.

Realized 98.2% fidelity in quantum state transfer.

Successfully transmitted high-dimensional, encoded quantum states.

Abstract

Distributed quantum computing architectures require high-performance quantum interconnects between quantum information processing units, while previous implementations have been fundamentally limited by transmission line losses. Here, we demonstrate a low-loss interconnect between two superconducting modules using an aluminum coaxial cable, achieving a bus mode quality factor of 1.7e6. By employing SNAIL as couplers, we realize inter-modular state transfer in 0.8 {\mu}s via a three-wave mixing process. The state transfer fidelity reaches 98.2% for quantum states encoded in the first two energy levels, achieving a Bell state fidelity of 92.5%. Furthermore, we show the capability to transfer high-dimensional states by successfully transmitting binomially encoded logical states. Systematic characterization reveals that performance constraints have shifted from transmission line losses (contributing merely 0.2% infidelity) to module-channel interface effects and local Kerr nonlinearities. Our work advances the realization of quantum interconnects approaching fundamental capacity limits, paving the way for scalable distributed quantum computing and efficient quantum communications.