# Experimental demonstration of single-shot quantum and classical signal transmission on single wavelength optical pulse

## TL;DR

This paper demonstrates the simultaneous transmission of classical data and secure quantum keys over a single optical fiber using a novel coherent displacement state generator, integrating quantum security into classical communication systems.

## Contribution

It introduces a method to embed CV-QKD signals within classical signals, enabling secure quantum communication alongside classical data on the same wavelength.

## Key findings

- Successful 25 km transmission of combined signals
- Use of a novel coherent displacement state generator
- Potential for practical quantum-secure communication systems

## Abstract

Advances in highly sensitive detection techniques for classical coherent communication systems have reduced the received signal power requirements to a few photons per bit. At this level one can take advantage of the quantum noise to create secure communication, using continuous variable quantum key distribution (CV-QKD). In this work therefore we embed CV-QKD signals within classical signals and transmit classical data and secure keys simultaneously over 25km of optical fibre. This is achieved by using a novel coherent displacement state generator, which has the potential for being used in a wide range of quantum optical experiments. This approach removes the need for separate channels for quantum communication systems and allows reduced system bandwidth for a given communications specification. This demonstration therefore demonstrates a way of implementing direct quantum physical layer security within a conventional classical communications system, offering a major advance in term of practical and low cost implementation.