206 research outputs found
A high-speed multi-protocol quantum key distribution transmitter based on a dual-drive modulator
We propose a novel source based on a dual-drive modulator that is adaptable
and allows Alice to choose between various practical quantum key distribution
(QKD) protocols depending on what receiver she is communicating with.
Experimental results show that the proposed transmitter is suitable for
implementation of the Bennett and Brassard 1984 (BB84), coherent one-way (COW)
and differential phase shift (DPS) protocols with stable and low quantum bit
error rate. This could become a useful component in network QKD, where
multi-protocol capability is highly desirable.Comment: 15 pages, 7 figure
Security of quantum key distribution with imperfect devices
We prove the security of the Bennett-Brassard (BB84) quantum key distribution
protocol in the case where the source and detector are under the limited
control of an adversary. Our proof applies when both the source and the
detector have small basis-dependent flaws, as is typical in practical
implementations of the protocol. We derive a general lower bound on the
asymptotic key generation rate for weakly basis-dependent eavesdropping
attacks, and also estimate the rate in some special cases: sources that emit
weak coherent states with random phases, detectors with basis-dependent
efficiency, and misaligned sources and detectors.Comment: 22 pages. (v3): Minor changes. (v2): Extensively revised and
expanded. New results include a security proof for generic small flaws in the
source and the detecto
Implementation vulnerabilities in general quantum cryptography
Quantum cryptography is information-theoretically secure owing to its solid
basis in quantum mechanics. However, generally, initial implementations with
practical imperfections might open loopholes, allowing an eavesdropper to
compromise the security of a quantum cryptographic system. This has been shown
to happen for quantum key distribution (QKD). Here we apply experience from
implementation security of QKD to several other quantum cryptographic
primitives. We survey quantum digital signatures, quantum secret sharing,
source-independent quantum random number generation, quantum secure direct
communication, and blind quantum computing. We propose how the eavesdropper
could in principle exploit the loopholes to violate assumptions in these
protocols, breaking their security properties. Applicable countermeasures are
also discussed. It is important to consider potential implementation security
issues early in protocol design, to shorten the path to future applications.Comment: 13 pages, 8 figure
Security proof of quantum key distribution with detection efficiency mismatch
In theory, quantum key distribution (QKD) offers unconditional security based
on the laws of physics. However, as demonstrated in recent quantum hacking
theory and experimental papers, detection efficiency loophole can be fatal to
the security of practical QKD systems. Here, we describe the physical origin of
detection efficiency mismatch in various domains including spatial, spectral,
and time domains and in various experimental set-ups. More importantly, we
prove the unconditional security of QKD even with detection efficiency
mismatch. We explicitly show how the key generation rate is characterized by
the maximal detection efficiency ratio between the two detectors. Furthermore,
we prove that by randomly switching the bit assignments of the detectors, the
effect of detection efficiency mismatch can be completely eliminated.Comment: 35 pages, 7 figure
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