5 research outputs found
Boosting up quantum key distribution by learning statistics of practical single photon sources
We propose a simple quantum-key-distribution (QKD) scheme for practical
single photon sources (SPSs), which works even with a moderate suppression of
the second-order correlation of the source. The scheme utilizes a
passive preparation of a decoy state by monitoring a fraction of the signal via
an additional beam splitter and a detector at the sender's side to monitor
photon number splitting attacks. We show that the achievable distance increases
with the precision with which the sub-Poissonian tendency is confirmed in
higher photon number distribution of the source, rather than with actual
suppression of the multi-photon emission events. We present an example of the
secure key generation rate in the case of a poor SPS with , in
which no secure key is produced with the conventional QKD scheme, and show that
learning the photon-number distribution up to several numbers is sufficient for
achieving almost the same achievable distance as that of an ideal SPS.Comment: 11 pages, 3 figures; published version in New J. Phy
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
Detector decoy quantum key distribution
Photon number resolving detectors can enhance the performance of many
practical quantum cryptographic setups. In this paper, we employ a simple
method to estimate the statistics provided by such a photon number resolving
detector using only a threshold detector together with a variable attenuator.
This idea is similar in spirit to that of the decoy state technique, and is
specially suited for those scenarios where only a few parameters of the photon
number statistics of the incoming signals have to be estimated. As an
illustration of the potential applicability of the method in quantum
communication protocols, we use it to prove security of an entanglement based
quantum key distribution scheme with an untrusted source without the need of a
squash model and by solely using this extra idea. In this sense, this detector
decoy method can be seen as a different conceptual approach to adapt a single
photon security proof to its physical, full optical implementation. We show
that in this scenario the legitimate users can now even discard the double
click events from the raw key data without compromising the security of the
scheme, and we present simulations on the performance of the BB84 and the
6-state quantum key distribution protocols.Comment: 27 pages, 7 figure