5,143 research outputs found
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
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 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
600 km repeater-like quantum communications with dual-band stabilisation
Twin-field (TF) quantum key distribution (QKD) could fundamentally alter the
rate-distance relationship of QKD, offering the scaling of a single-node
quantum repeater. Although recent experiments have demonstrated the potential
of TF-QKD, formidable challenges remain for its real world use. In particular,
new methods are needed to extend both the distance beyond 500 km and key rates
above current milli-bit per second values. Previous demonstrations have
required intense stabilisation signals at the same wavelength as the quantum
channel, thereby unavoidably generating noise due to Rayleigh scattering that
limits the distance and bit rate. Here, we introduce a novel dual band
stabilisation scheme based on wavelength division multiplexing that allows us
to circumvent past limitations. An intense stabilisation signal that is
spectrally isolated from the quantum channel is used to reduce the phase drift
by three orders of magnitude, while a second, much weaker reference at the
quantum wavelength locks the channel phase to a predetermined value. With this
strategy, we realise a low noise implementation suitable for all the variants
of TF-QKD protocols proposed so far and capable of generating real strings of
bits for the first time. The setup provides repeater-like key rates over record
communication distances of 555 km and 605 km in the finite-size and asymptotic
regimes, respectively, and increases the secure key rate at long distance by
two orders of magnitude to values of practical significance.Comment: 14 pages, 5 figures. Methods and supplementary materials are include
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
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