Motion-Compensated Handheld Quantum Key Distribution System

TL;DR

This paper demonstrates a handheld quantum key distribution system capable of secure, high-rate key transmission in real-world conditions, overcoming challenges like device misalignment and ambient light.

Contribution

It introduces a novel handheld QKD system with dynamic beam-steering and reference-frame-independent encoding achieving practical secret key rates.

Findings

Secret key rate above 30 kb/s over 0.5 meters

Operates effectively under ambient light conditions

First demonstration of handheld QKD transmission

Abstract

Mobile devices have become an inseparable part of our everyday life. They are used to transmit an ever-increasing amount of sensitive health, financial and personal information. This exposes us to the growing scale and sophistication of cyber-attacks. Quantum Key Distribution (QKD) can provide unconditional and future-proof data security but implementing it for handheld mobile devices comes with specific challenges. To establish security, secret keys of sufficient length need to be transmitted during the time of a handheld transaction (~1s) despite device misalignment, ambient light and user's inevitable hand movements. Transmitters and receivers should ideally be compact and low-cost, while avoiding security loopholes. Here we demonstrate the first QKD transmission from a handheld transmitter with a key-rate large enough to overcome finite key effects. Using dynamic beam-steering, reference-frame-independent encoding and fast indistinguishable pulse generation, we obtain a secret key rate above 30kb/s over a distance of 0.5m under ambient light conditions.