# Quantum State Transfer from a Single Photon to a Distant Quantum-Dot Electron Spin

## TL;DR

This paper demonstrates quantum state transfer from a single photon to a distant quantum-dot electron spin with high fidelity, advancing quantum network capabilities through controlled frequency bin manipulation and entanglement measurement.

## Contribution

It introduces a method for coherent control of photon frequency bins and achieves quantum state transfer with high fidelity between photonic and electron spin qubits over 5 meters.

## Key findings

- Achieved spin-photon entanglement fidelity of 0.796
- Demonstrated quantum state transfer with 78.5% fidelity
- Controlled photon frequency bins using electro-optic modulators

## Abstract

Quantum state transfer from flying photons to stationary matter qubits is an important element in the realization of quantum networks. Self-assembled semiconductor quantum dots provide a promising solid-state platform hosting both single photon and spin, with an inherent light-matter interface. Here, we develop a method to coherently and actively control the single-photon frequency bins in superposition using electro-optic modulators, and measure the spin-photon entanglement with a fidelity of $0.796\pm0.020$. Further, by Greenberger-Horne-Zeilinger-type state projection on the frequency, path and polarization degrees of freedom of a single photon, we demonstrate quantum state transfer from a single photon to a single electron spin confined in an InGaAs quantum dot, separated by 5 meters. The quantum state mapping from the photon's polarization to the electron's spin is demonstrated along three different axis on the Bloch sphere, with an average fidelity of $78.5\%$.