5 research outputs found
High rate, long-distance quantum key distribution over 250km of ultra low loss fibres
We present a fully automated quantum key distribution prototype running at
625 MHz clock rate. Taking advantage of ultra low loss fibres and low-noise
superconducting detectors, we can distribute 6,000 secret bits per second over
100 km and 15 bits per second over 250km
Entangled Quantum Key Distribution with a Biased Basis Choice
We investigate a quantum key distribution (QKD) scheme which utilizes a
biased basis choice in order to increase the efficiency of the scheme. The
optimal bias between the two measurement bases, a more refined error analysis,
and finite key size effects are all studied in order to assure the security of
the final key generated with the system. We then implement the scheme in a
local entangled QKD system that uses polarization entangled photon pairs to
securely distribute the key. A 50/50 non-polarizing beamsplitter with different
optical attenuators is used to simulate a variable beamsplitter in order to
allow us to study the operation of the system for different biases. Over 6
hours of continuous operation with a total bias of 0.9837/0.0163 (Z/X), we were
able to generate 0.4567 secure key bits per raw key bit as compared to 0.2550
secure key bits per raw key bit for the unbiased case. This represents an
increase in the efficiency of the key generation rate by 79%.Comment: v2: Revised paper based on referee reports, Theory section was
revised (primarily regarding finite key effects), Results section almost
completely rewritten with more experimental data. 16 pages, 5 figures. v1: 14
pages, 6 figures, higher resolution figures will be available in the
published articl
Composability in quantum cryptography
In this article, we review several aspects of composability in the context of
quantum cryptography. The first part is devoted to key distribution. We discuss
the security criteria that a quantum key distribution protocol must fulfill to
allow its safe use within a larger security application (e.g., for secure
message transmission). To illustrate the practical use of composability, we
show how to generate a continuous key stream by sequentially composing rounds
of a quantum key distribution protocol. In a second part, we take a more
general point of view, which is necessary for the study of cryptographic
situations involving, for example, mutually distrustful parties. We explain the
universal composability framework and state the composition theorem which
guarantees that secure protocols can securely be composed to larger
applicationsComment: 18 pages, 2 figure
Decoy-state quantum key distribution with both source errors and statistical fluctuations
We show how to calculate the fraction of single photon counts of the
3-intensity decoy-state quantum cryptography faithfully with both statistical
fluctuations and source errors. Our results only rely on the bound values of a
few parameters of the states of pulses.Comment: Published version with revision