# Realization of a cascaded quantum system: heralded absorption of a single photon qubit by a single-electron charged quantum dot

## TL;DR

This paper demonstrates a heralded quantum state transfer between two quantum dots separated by 5 meters, using a measurement that confirms successful transfer without revealing qubit information, advancing quantum network capabilities.

## Contribution

It introduces a method for heralded absorption of a photonic qubit by a distant quantum dot, enabling quantum information transfer without qubit information leakage.

## Key findings

- Successful heralded absorption of a single-photon qubit by a distant quantum dot.
- Quantum information transfer occurs without revealing the qubit state.
- Potential for new quantum information protocols using cascaded quantum systems.

## Abstract

Photonic losses pose a major limitation for implementation of quantum state transfer between nodes of a quantum network. A measurement that heralds successful transfer without revealing any information about the qubit may alleviate this limitation. Here, we demonstrate heralded absorption of a single photonic qubit generated by a single neutral quantum dot, by a single-electron charged quantum dot that is located 5 meters away. The transfer of quantum information to the spin degree of freedom takes place upon emission of a photon: for a properly chosen or prepared quantum dot, detection of this photon yields no information about the qubit. We show that this process can be combined with local operations optically performed on the destination node, by measuring classical correlations between the absorbed photon color and the final state of the electron spin. Our work suggests alternative avenues for realization of quantum information protocols based on cascaded quantum systems.