2,452 research outputs found
Darwin -— an experimental astronomy mission to search for extrasolar planets
As a response to ESA call for mission concepts for its Cosmic Vision 2015–2025 plan, we propose a mission called Darwin. Its primary goal is the study of terrestrial extrasolar planets and the search for life on them. In this paper, we describe different characteristics of the instrument
Orbital angular momentum of photons and the entanglement of Laguerre-Gaussian modes
The identification of orbital angular momentum (OAM) as a fundamental
property of a beam of light nearly twenty-five years ago has led to an
extensive body of research around this topic. The possibility that single
photons can carry OAM has made this degree of freedom an ideal candidate for
the investigation of complex quantum phenomena and their applications. Research
in this direction has ranged from experiments on complex forms of quantum
entanglement to the interaction between light and quantum states of matter.
Furthermore, the use of OAM in quantum information has generated a lot of
excitement, as it allows for encoding large amounts of information on a single
photon. Here we explain the intuition that led to the first quantum experiment
with OAM fifteen years ago. We continue by reviewing some key experiments
investigating fundamental questions on photonic OAM and the first steps into
applying these properties in novel quantum protocols. In the end, we identify
several interesting open questions that could form the subject of future
investigations with OAM.Comment: 17 pages, 7 figures; close to accepted versio
A Short Wavelength GigaHertz Clocked Fiber-Optic Quantum Key Distribution System
A quantum key distribution system has been developed, using standard
telecommunications optical fiber, which is capable of operating at clock rates
of greater than 1 GHz. The quantum key distribution system implements a
polarization encoded version of the B92 protocol. The system employs
vertical-cavity surface-emitting lasers with emission wavelengths of 850 nm as
weak coherent light sources, and silicon single photon avalanche diodes as the
single photon detectors. A distributed feedback laser of emission wavelength
1.3 micro-metres, and a linear gain germanium avalanche photodiode was used to
optically synchronize individual photons over the standard telecommunications
fiber. The quantum key distribution system exhibited a quantum bit error rate
of 1.4%, and an estimated net bit rate greater than 100,000 bits-per-second for
a 4.2 km transmission range. For a 10 km fiber range a quantum bit error rate
of 2.1%, and estimated net bit rate of greater than 7,000 bits-per-second was
achieved.Comment: Pre-press versio
Programmable multiport optical circuits in opaque scattering materials
We propose and experimentally verify a method to program the effective
transmission matrix of general multiport linear optical circuits in random
multiple-scattering materials by phase modulation of incident wavefronts. We
demonstrate the power of our method by programming linear optical circuits in
white paint layers with 2 inputs and 2 outputs, and 2 inputs and 3 outputs.
Using interferometric techniques we verify our ability to program any desired
phase relation between the outputs. The method works in a deterministic manner
and can be directly applied to existing wavefront-shaping setups without the
need of measuring a transmission matrix or to rely on sensitive interference
measurements.Comment: 14 pages, 7 figure
Photon temporal modes: a complete framework for quantum information science
Field-orthogonal temporal modes of photonic quantum states provide a new
framework for quantum information science (QIS). They intrinsically span a
high-dimensional Hilbert space and lend themselves to integration into existing
single-mode fiber communication networks. We show that the three main
requirements to construct a valid framework for QIS -- the controlled
generation of resource states, the targeted and highly efficient manipulation
of temporal modes and their efficient detection -- can be fulfilled with
current technology. We suggest implementations of diverse QIS applications
based on this complete set of building blocks.Comment: 17 pages, 13 figure
Analysis of detector performance in a gigahertz clock rate quantum key distribution system
We present a detailed analysis of a gigahertz clock rate environmentally robust phase-encoded quantum key distribution (QKD) system utilizing several different single-photon detectors, including the first implementation of an experimental resonant cavity thin-junction silicon single-photon avalanche diode. The system operates at a wavelength of 850 nm using standard telecommunications optical fibre. A general-purpose theoretical model for the performance of QKD systems is presented with reference to these experimental results before predictions are made about realistic detector developments in this system. We discuss, with reference to the theoretical model, how detector operating parameters can be further optimized to maximize key exchange rates
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