593 research outputs found
Space division multiplexing chip-to-chip quantum key distribution
Quantum cryptography is set to become a key technology for future secure
communications. However, to get maximum benefit in communication networks,
transmission links will need to be shared among several quantum keys for
several independent users. Such links will enable switching in quantum network
nodes of the quantum keys to their respective destinations. In this paper we
present an experimental demonstration of a photonic integrated silicon chip
quantum key distribution protocols based on space division multiplexing (SDM),
through multicore fiber technology. Parallel and independent quantum keys are
obtained, which are useful in crypto-systems and future quantum network
Experimental demonstration of the DPTS QKD protocol over a 170 km fiber link
Quantum key distribution (QKD) is a promising technology aiming at solving
the security problem arising from the advent of quantum computers. While the
main theoretical aspects are well developed today, limited performances, in
terms of achievable link distance and secret key rate, are preventing the
deployment of this technology on a large scale. More recent QKD protocols,
which use multiple degrees of freedom for the encoding of the quantum states,
allow an enhancement of the system performances. Here, we present the
experimental demonstration of the differential phase-time shifting protocol
(DPTS) up to 170 km of fiber link. We compare its performance with the
well-known coherent one-way (COW) and the differential phase shifting (DPS)
protocols, demonstrating a higher secret key rate up to 100 km. Moreover, we
propagate a classical signal in the same fiber, proving the compatibility of
quantum and classical light.Comment: 5 pages, 3 figures, journal pape
High-Dimensional Quantum Key Distribution based on Multicore Fiber using Silicon Photonic Integrated Circuits
Quantum Key Distribution (QKD) provides an efficient means to exchange
information in an unconditionally secure way. Historically, QKD protocols have
been based on binary signal formats, such as two polarisation states, and the
transmitted information efficiency of the quantum key is intrinsically limited
to 1 bit/photon. Here we propose and experimentally demonstrate, for the first
time, a high-dimensional QKD protocol based on space division multiplexing in
multicore fiber using silicon photonic integrated lightwave circuits. We
successfully realized three mutually unbiased bases in a four-dimensional
Hilbert space, and achieved low and stable quantum bit error rate well below
both coherent attack and individual attack limits. Compared to previous
demonstrations, the use of a multicore fiber in our protocol provides a much
more efficient way to create high-dimensional quantum states, and enables
breaking the information efficiency limit of traditional QKD protocols. In
addition, the silicon photonic circuits used in our work integrate variable
optical attenuators, highly efficient multicore fiber couplers, and
Mach-Zehnder interferometers, enabling manipulating high-dimensional quantum
states in a compact and stable means. Our demonstration pave the way to utilize
state-of-the-art multicore fibers for long distance high-dimensional QKD, and
boost silicon photonics for high information efficiency quantum communications.Comment: Please see the complementary work arXiv:1610.01682 (2016
All-optical 160 Gbit/s RZ data retiming system incorporating a pulse shaping fibre Bragg grating
We characterize a 160Gbit/s retimer based on flat-topped pulses shaped using a superstructured fibre Bragg grating. The benefits of using shaped rather than conventional pulse forms in terms of timing jitter reduction are confirmed by bit-error-rate measurements
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