Upper bounds on the rate in device-independent quantum key distribution

Matthias Christandl, Roberto Ferrara, Karol Horodecki

Published May 27, 2020• 3 citations

Abstract

Quantum key distribution (QKD) is a method to distribute secret key among sender and receiver by the transmission of quantum particles (e.g. photons). Device-independent quantum key distribution (DIQKD) is a version of quantum key distribution with a stronger security demand in that sender and receiver do not need to rely on the inner workings of their device, which consequently can come from an untrusted vendor. We study the rate at which DIQKD can be carried out for a given quantum channel connecting sender and receiver and provide a technique to upper bound the achievable rate. As a result, we show that the rate of device independent secure key can for some channels be much smaller (even arbitrarily so) than that of QKD. We do so, by first providing definition of device independent secure key rate, which is of independent interest. For bipartite states we formulate a sufficient condition for a gap between QKD and DIQKD key rates and examples of 8-qubit bipartite state exhibiting the gap between device dependent and device independent key.

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