8 research outputs found
Finite-key analysis of the six-state protocol with photon-number-resolution detectors
The six-state protocol is a discrete-variable protocol for quantum key
distribution, that permits to tolerate a noisier channel than the BB84
protocol. In this work we provide a lower bound on the maximum achievable key
rate of a practical implementation of the entanglement-based version of the
six-state protocol. Regarding the experimental set-up we consider that the
source is untrusted and the photon-number statistics is measured using
photon-number-resolving detectors. We provide the formula for the key rate for
a finite initial number of resources. As an illustration of the considered
formalism, we calculate the key rate for the setting where the source produces
entangled photon pairs via parametric down-conversion and the losses in the
channel depend on the distance. As a result we find that the finite-key
corrections for the considered scenario are not negligible and they should be
considered in any practical analysis
Quantum repeaters and quantum key distribution: analysis of secret key rates
We analyze various prominent quantum repeater protocols in the context of
long-distance quantum key distribution. These protocols are the original
quantum repeater proposal by Briegel, D\"ur, Cirac and Zoller, the so-called
hybrid quantum repeater using optical coherent states dispersively interacting
with atomic spin qubits, and the Duan-Lukin-Cirac-Zoller-type repeater using
atomic ensembles together with linear optics and, in its most recent extension,
heralded qubit amplifiers. For our analysis, we investigate the most important
experimental parameters of every repeater component and find their minimally
required values for obtaining a nonzero secret key. Additionally, we examine in
detail the impact of device imperfections on the final secret key rate and on
the optimal number of rounds of distillation when the entangled states are
purified right after their initial distribution.Comment: Published versio
QKD with finite resources: secret key rates via R\'enyi entropies
A realistic Quantum Key Distribution (QKD) protocol necessarily deals with
finite resources, such as the number of signals exchanged by the two parties.
We derive a bound on the secret key rate which is expressed as an optimization
problem over R\'enyi entropies. Under the assumption of collective attacks by
an eavesdropper, a computable estimate of our bound for the six-state protocol
is provided. This bound leads to improved key rates in comparison to previous
results.Comment: 11 pages, 2 figure