1,414 research outputs found
Source attack of decoy-state quantum key distribution using phase information
Quantum key distribution (QKD) utilizes the laws of quantum mechanics to
achieve information-theoretically secure key generation. This field is now
approaching the stage of commercialization, but many practical QKD systems
still suffer from security loopholes due to imperfect devices. In fact,
practical attacks have successfully been demonstrated. Fortunately, most of
them only exploit detection-side loopholes which are now closed by the recent
idea of measurement-device-independent QKD. On the other hand, little attention
is paid to the source which may still leave QKD systems insecure. In this work,
we propose and demonstrate an attack that exploits a source-side loophole
existing in qubit-based QKD systems using a weak coherent state source and
decoy states. Specifically, by implementing a linear-optics
unambiguous-state-discrimination measurement, we show that the security of a
system without phase randomization --- which is a step assumed in conventional
security analyses but sometimes neglected in practice --- can be compromised.
We conclude that implementing phase randomization is essential to the security
of decoy-state QKD systems under current security analyses.Comment: 12 pages, 5 figure
Field test of a practical secure communication network with decoy-state quantum cryptography
We present a secure network communication system that operated with
decoy-state quantum cryptography in a real-world application scenario. The full
key exchange and application protocols were performed in real time among three
nodes, in which two adjacent nodes were connected by approximate 20 km of
commercial telecom optical fiber. The generated quantum keys were immediately
employed and demonstrated for communication applications, including unbreakable
real-time voice telephone between any two of the three communication nodes, or
a broadcast from one node to the other two nodes by using one-time pad
encryption.Comment: 10 pages, 2 figures, 2 tables, typos correcte
Metropolitan all-pass and inter-city quantum communication network
We have demonstrated a metropolitan all-pass quantum communication network in
field fiber for four nodes. Any two nodes of them can be connected in the
network to perform quantum key distribution (QKD). An optical switching module
is presented that enables arbitrary 2-connectivity among output ports.
Integrated QKD terminals are worked out, which can operate either as a
transmitter, a receiver, or even both at the same time. Furthermore, an
additional link in another city of 60 km fiber (up to 130 km) is seamless
integrated into this network based on a trusted relay architecture. On all the
links, we have implemented protocol of decoy state scheme. All of necessary
electrical hardware, synchronization, feedback control, network software,
execution of QKD protocols are made by tailored designing, which allow a
completely automatical and stable running. Our system has been put into
operation in Hefei in August 2009, and publicly demonstrated during an
evaluation conference on quantum network organized by the Chinese Academy of
Sciences on August 29, 2009. Real-time voice telephone with one-time pad
encoding between any two of the five nodes (four all-pass nodes plus one
additional node through relay) is successfully established in the network
within 60km.Comment: 9 pages, 2 figures, 2 table
High-speed measurement-device-independent quantum key distribution with integrated silicon photonics
Measurement-device-independent quantum key distribution (MDI-QKD) removes all
detector side channels and enables secure QKD with an untrusted relay. It is
suitable for building a star-type quantum access network, where the complicated
and expensive measurement devices are placed in the central untrusted relay and
each user requires only a low-cost transmitter, such as an integrated photonic
chip. Here, we experimentally demonstrate a 1.25 GHz silicon photonic
chip-based MDI-QKD system using polarization encoding. The photonic chip
transmitters integrate the necessary encoding components for a standard QKD
source. We implement random modulations of polarization states and decoy
intensities, and demonstrate a finite-key secret rate of 31 bps over 36 dB
channel loss (or 180 km standard fiber). This key rate is higher than
state-of-the-art MDI-QKD experiments. The results show that silicon photonic
chip-based MDI-QKD, benefiting from miniaturization, low-cost manufacture and
compatibility with CMOS microelectronics, is a promising solution for future
quantum secure networks.Comment: 30 pages, 12 figure
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