Device Independent Quantum Key Activation

TL;DR

This paper introduces the concept of device-independent key activation, showing how multiple copies of a quantum distribution can be combined via classical wiring to enable secure key distribution where it was previously impossible.

Contribution

It demonstrates that combining several copies of a quantum distribution through local classical wiring can activate device-independent quantum key distribution capabilities.

Findings

Activation of DIQKD from useless distributions is possible.

Wiring multiple copies can increase the key rate.

Semi-definite programming bounds support the activation process.

Abstract

Device-independent quantum key distribution (DIQKD) allows two distant parties to establish a secret key, based only on the observed Bell nonlocal distribution. It remains however, unclear what the minimal resources for enabling DIQKD are and how to maximize the key rate from a given distribution. In the present work, we consider a scenario where several copies of a given quantum distribution are jointly processed via a local and classical wiring operation. We find that, under few assumptions, it is possible to activate device-independent key. That is, starting from a distribution that is useless in a DIQKD protocol, we obtain a positive key rate by wiring several copies together. We coin this effect device-independent key activation. Our analysis focuses on the standard DIQKD protocol with one-way post-processing, and we resort to semi-definite programming techniques for computing lower bounds on the key rate.