Intracity quantum communication via thermal microwave networks

TL;DR

This paper proposes a novel protocol for quantum communication over microwave networks using thermal channels, enabling secure quantum state transfer within cities with existing superconducting technology.

Contribution

It introduces a general protocol for quantum state transfer through thermal microwave channels, even with high thermal photon numbers, suitable for practical superconducting circuits.

Findings

Quantum states can be transmitted over ~100 m microwave lines at 4K.

The protocol works with channels having many thermal photons.

Enables intra-city quantum networks using microwave technology.

Abstract

Communication over proven-secure quantum channels is potentially one of the most wide-ranging applications of currently developed quantum technologies. It is generally envisioned that in future quantum networks, separated nodes containing stationary solid-state or atomic qubits are connected via the exchange of optical photons over large distances. In this work we explore an intriguing alternative for quantum communication via all-microwave networks. To make this possible, we describe a general protocol for sending quantum states through thermal channels, even when the number of thermal photons in the channel is much larger than one. The protocol can be implemented with state-of-the-art superconducting circuits and enables the transfer of quantum states over distances of ~100 m via microwave transmission lines cooled to only T=4K. This opens up completely new possibilities for quantum communication within and across buildings, and consequently, for the implementation of intra-city quantum networks based on microwave technology only.