79,532 research outputs found
Fully Device-Independent Quantum Key Distribution
Quantum cryptography promises levels of security that are impossible to replicate in a classical world. Can this security be guaranteed even when the quantum devices on which the protocol relies are untrusted? This central question dates back to the early 1990s when the challenge of achieving device-independent quantum key distribution was first formulated. We answer this challenge by rigorously proving the device-independent security of a slight variant of Ekert's original entanglement-based protocol against the most general (coherent) attacks. The resulting protocol is robust: While assuming only that the devices can be modeled by the laws of quantum mechanics and are spatially isolated from each other and from any adversary's laboratory, it achieves a linear key rate and tolerates a constant noise rate in the devices. In particular, the devices may have quantum memory and share arbitrary quantum correlations with the eavesdropper. The proof of security is based on a new quantitative understanding of the monogamous nature of quantum correlations in the context of a multiparty protocol
Fully passive Measurement Device Independent Quantum Key Distribution
Measurement-device-independent quantum key distribution (MDI-QKD) can resist
all attacks on the detection devices, but there are still some security issues
related to the source side. One possible solution is to use the passive
protocol to eliminate the side channels introduced by active modulators at the
source. Recently, a fully passive QKD protocol has been proposed that can
simultaneously achieve passive encoding and passive decoy-state modulation
using linear optics. In this work, we propose a fully passive MDI-QKD scheme
that can protect the system from both side channels of source modulators and
attacks on the measurement devices, which can significantly improve the
implementation security of the QKD systems. We provide a specific passive
encoding strategy and a method for decoy-state analysis, followed by simulation
results for the secure key rate in the asymptotic scenario. Our work offers a
feasible way to improve the implementation security of QKD systems, and serves
as a reference for achieving passive QKD schemes using realistic devices
Fully Device-Independent Quantum Key Distribution Using Synchronous Correlations
We derive a device-independent quantum key distribution protocol based on synchronous correlations and their Bell inequalities. This protocol offers several advantages over other device-independent schemes including symmetry between the two users and no need for pre-shared randomness. We close a "synchronicity" loophole by showing that an almost synchronous correlation inherits the self-testing property of the associated synchronous correlation. We also pose a new security assumption that closes the "locality" (or "causality") loophole: an unbounded adversary with even a small uncertainty about the users\u27 choice of measurement bases cannot produce any almost synchronous correlation that approximately maximally violates a synchronous Bell inequality
Semi-device-independent security of one-way quantum key distribution
By testing nonlocality, the security of entanglement-based quantum key
distribution (QKD) can be enhanced to being 'device-independent'. Here we ask
whether such a strong form of security could also be established for one-way
(prepare and measure) QKD. While fully device-independent security is
impossible, we show that security can be guaranteed against individual attacks
in a semi-device-independent scenario. In the latter, the devices used by the
trusted parties are non-characterized, but the dimensionality of the quantum
systems used in the protocol is assumed to be bounded. Our security proof
relies on the analogies between one-way QKD, dimension witnesses and
random-access codes.Comment: 5 pages, 1 figur
Detection loophole attacks on semi-device-independent quantum and classical protocols
Semi-device-independent quantum protocols realize information tasks - e.g.
secure key distribution, random access coding, and randomness generation - in a
scenario where no assumption on the internal working of the devices used in the
protocol is made, except their dimension. These protocols offer two main
advantages: first, their implementation is often less demanding than
fully-device-independent protocols. Second, they are more secure than their
device-dependent counterparts. Their classical analogous is represented by
random access codes, which provide a general framework for describing one-sided
classical communication tasks. We discuss conditions under which detection
inefficiencies can be exploited by a malicious provider to fake the performance
of semi-device-independent quantum and classical protocols - and how to prevent
it.Comment: 13 pages, 1 figure, published versio
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