Quantum communication with itinerant surface acoustic wave phonons

TL;DR

This paper demonstrates a quantum communication system using surface acoustic wave phonons to coherently transfer quantum information between two separate superconducting qubit nodes, showcasing high-fidelity state transfer and entanglement generation.

Contribution

It introduces a novel quantum communication platform utilizing itinerant surface acoustic wave phonons for coherent node-to-node quantum information transfer.

Findings

High-fidelity quantum state transfer achieved

Generation of a two-node Bell state demonstrated

Observed dispersive phonon-qubit interactions

Abstract

Surface acoustic waves are commonly used in classical electronics applications, and their use in quantum systems is beginning to be explored, as evidenced by recent experiments using acoustic Fabry-P\'erot resonators. Here we explore their use for quantum communication, where we demonstrate a single-phonon surface acoustic wave transmission line, which links two physically-separated qubit nodes. Each node comprises a microwave phonon transducer, an externally-controlled superconducting variable coupler, and a superconducting qubit. Using this system, precisely-shaped individual itinerant phonons are used to coherently transfer quantum information between the two physically-distinct quantum nodes, enabling the high-fidelity node-to-node transfer of quantum states as well as the generation of a two-node Bell state. We further explore the dispersive interactions between an itinerant phonon emitted from one node and interacting with the superconducting qubit in the remote node. The observed interactions between the phonon and the remote qubit promise future quantum optics-style experiments with itinerant phonons.