4,189 research outputs found
Quantum key distribution over 658 km fiber with distributed vibration sensing
Twin-field quantum key distribution (TF-QKD) promises ultra-long secure key
distribution which surpasses the rate distance limit and can reduce the number
of the trusted nodes in long-haul quantum network. Tremendous efforts have been
made towards implementation of TF-QKD, among which, the secure key with finite
size analysis can distribute more than 500 km in the lab and in the field.
Here, we demonstrate the sending-or-not-sending TF-QKD experimentally,
achieving a secure key distribution with finite size analysis over 658 km
ultra-low-loss optical fiber, improve the secure distance record by around 100
km. Meanwhile, in a TF-QKD system, any phase fluctuation due to temperature
variation and ambient variation during the channel must be recorded and
compensated, and all these phase information can then be utilized to sense the
channel vibration perturbations. With our QKD system, we recovered the external
vibrational perturbations on the fiber generated by an artificial vibroseis and
successfully located the perturbation position with a resolution better than 1
km. Our results not only set a new distance record of QKD, but also demonstrate
that the redundant information of TF-QKD can be used for remote sensing of the
channel vibration, which can find applications in earthquake detection and
landslide monitoring besides secure communication.Comment: 20 pages, 4 figures and 1 tabl
Twin-field quantum key distribution with local frequency reference
Twin-field quantum key distribution (TF-QKD) overcomes the linear rate-loss
limit, which promises a boost of secure key rate over long distance. However,
the complexity of eliminating the frequency differences between the independent
laser sources hinders its practical application. Here, taking the saturated
absorption spectroscopy of acetylene as an absolute reference, we propose and
demonstrate a simple and practical approach to realize TF-QKD without requiring
relative frequency control of the independent laser sources. Adopting the
4-intensity sending-or-not-sending TF-QKD protocol, we experimentally
demonstrate the TF-QKD over 502 km, 301 km and 201 km ultra-low loss optical
fiber respectively. We expect this high-performance scheme will find widespread
usage in future intercity and free-space quantum communication networks.Comment: 13 pages, 5 figures, 7 table
Experimental Side-Channel-Free Quantum Key Distribution
Quantum key distribution can provide unconditionally secure key exchange for
remote users in theory. In practice, however, in most quantum key distribution
systems, quantum hackers might steal the secure keys by listening to the side
channels in the source, such as the photon frequency spectrum, emission time,
propagation direction, spatial angular momentum, and so on. It is hard to
prevent such kinds of attacks because side channels may exist in any of the
encoding space whether the designers take care of or not. Here we report an
experimental realization of a side-channel-free quantum key distribution
protocol which is not only measurement-device-independent, but also immune to
all side-channel attacks in the source. We achieve a secure key rate of 4.80e-7
per pulse through 50 km fiber spools.Comment: 23 pages, 5 figure
Twin-field quantum key distribution without optical frequency dissemination
Twin-field (TF) quantum key distribution (QKD) has rapidly risen as the most
viable solution to long-distance secure fibre communication thanks to its
fundamentally repeater-like rate-loss scaling. However, its implementation
complexity, if not successfully addressed, could impede or even prevent its
advance into real-world. To satisfy its requirement for twin-field coherence,
all present setups adopted essentially a gigantic, resource-inefficient
interferometer structure that lacks scalability that mature QKD systems provide
with simplex quantum links. Here we introduce a novel technique that can
stabilise an open channel without using a closed interferometer and has general
applicability to phase-sensitive quantum communications. Using locally
generated frequency combs to establish mutual coherence, we develop a simple
and versatile TF-QKD setup that does not need service fibre and can operate
over links of 100 km asymmetry. We confirm the setup's repeater-like behaviour
and obtain a finite-size rate of 0.32 bit/s at a distance of 615.6 km.Comment: 14 pages, 7 figure
Implementation security in quantum key distribution
The problem of implementation security in quantum key distribution (QKD)
refers to the difficulty of meeting the requirements of mathematical security
proofs in real-life QKD systems. Here, we provide a succint review on this
topic, focusing on discrete variable QKD setups. Particularly, we discuss some
of their main vulnerabilities and comment on possible approaches to overcome
them.Comment: Submitted to Advanced Quantum Technologie
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Quantum key distribution beyond the repeaterless secret key capacity
Quantum communications promise to provide information theoretic security in the exchange of information. However, unlike their classical counterpart, they utilise dim optical pulses whose amplification is prohibited. Consequently, their transmission rate and range is confined below a theoretical limit known as repeaterless secret key capacity. Overcoming this limit with today’s technology was believed to be impossible until the recent proposal of Twin-field (TF) quantum key distribution (QKD), a scheme that uses phase-coherent optical signals and an auxiliary measuring station to distribute quantum information. Here, TF-QKD and its main variations are initially explored and compared in simulations, to assess their performance in different attributes. Such schemes are also practically implemented for the first time in two experiments. The first is a proof-of-principle implementation over significant channel losses, in excess of 90 dB. In the second, the setup is developed further and the protocol is implemented over real fibre channels exceeding 600 km in length, representing the first fibre-based secure quantum communication beyond the barriers of 600 km and 100 dB. In both cases, in the high loss/distance regime, the resulting secure key rates exceed the repeaterless secret key capacity, a result never achieved before.EPSRC, Toshiba Research Europ
Phase Noise in Real-World Twin-Field Quantum Key Distribution
We investigate the impact of noise sources in real-world implementations of
Twin-Field Quantum Key Distribution (TF-QKD) protocols, focusing on phase noise
from photon sources and connecting fibers. Our work emphasizes the role of
laser quality, network topology, fiber length, arm balance, and detector
performance in determining key rates. Remarkably, it reveals that the leading
TF-QKD protocols are similarly affected by phase noise despite different
mechanisms. Our study demonstrates duty cycle improvements of over 2x through
narrow-linewidth lasers and phase-control techniques, highlighting the
potential synergy with high-precision time/frequency distribution services.
Ultrastable lasers, evolving toward integration and miniaturization, offer
promise for agile TF-QKD implementations on existing networks. Properly
addressing phase noise and practical constraints allows for consistent key rate
predictions, protocol selection, and layout design, crucial for establishing
secure long-haul links for the Quantum Communication Infrastructures under
development in several countries.Comment: 18 pages, 8 figures, 2 table
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