# Faithful conversion of propagating quantum information to mechanical motion

## TL;DR

This paper demonstrates a high-fidelity method to convert quantum information from propagating photons to mechanical resonators, a key step for quantum communication and computing architectures.

## Contribution

It introduces a quantum state conversion process with fidelity exceeding classical bounds, verified through quantum state tomography.

## Key findings

- Average process fidelity of 0.83+0.03-0.06
- Fidelity surpasses classical conversion limits
- Enables mechanical resonators in quantum networks

## Abstract

We convert propagating qubits encoded as superpositions of zero and one photons to the motion of a micrometer-sized mechanical resonator. Using quantum state tomography, we determine the density matrix of both the propagating photons and the mechanical resonator. By comparing a sufficient set of states before and after conversion, we determine the average process fidelity to be $F_{\textrm{avg}} = 0.83\substack{+0.03-0.06}$ which exceeds the classical bound for the conversion of an arbitrary qubit state. This conversion ability is necessary for using mechanical resonators in emerging quantum communication and modular quantum computation architectures.