Unconditionally secure device-independent quantum key distribution with only two devices

TL;DR

This paper presents a new device-independent quantum key distribution protocol that requires only one device per user, maintaining unconditional security despite practical limitations of previous methods.

Contribution

It introduces a novel protocol enabling secure quantum key distribution with only two devices, reducing the hardware complexity compared to prior protocols.

Findings

Protocol is unconditionally secure against malicious device suppliers.

Requires only one device per user, simplifying implementation.

Maintains security under locally enforced signaling constraints.

Abstract

Device-independent quantum key distribution is the task of using uncharacterized quantum devices to establish a shared key between two users. If a protocol is secure regardless of the device behaviour, it can be used to generate a shared key even if the supplier of the devices is malicious. To date, all device-independent quantum key distribution protocols that are known to be secure require separate isolated devices for each entangled pair, which is a significant practical limitation. We introduce a protocol that requires Alice and Bob to have only one device each. Although inefficient, our protocol is unconditionally secure against an adversarial supplier limited only by locally enforced signalling constraints.