31 research outputs found
Systematic study of the PDC speckle structure for quantum imaging applications
Sub shot noise imaging of weak object by exploiting Parametric Down Converted
light represents a very interesting technological development. A precise
characterization of PDC speckle structure in dependence of pump beam parameters
is a fundamental tool for this application. In this paper we present a first
set of data addressed to this purpose
Direct generation of photon triplets using cascaded photon-pair sources
Non-classical states of light, such as entangled photon pairs and number
states, are essential for fundamental tests of quantum mechanics and optical
quantum technologies. The most widespread technique for creating these quantum
resources is the spontaneous parametric down-conversion (SPDC) of laser light
into photon pairs. Conservation of energy and momentum in this process, known
as phase-matching, gives rise to strong correlations which are used to produce
two-photon entanglement in various degrees of freedom. It has been a
longstanding goal of the quantum optics community to realise a source that can
produce analogous correlations in photon triplets, but of the many approaches
considered, none have been technically feasible. In this paper we report the
observation of photon triplets generated by cascaded down-conversion. Here each
triplet originates from a single pump photon, and therefore quantum
correlations will extend over all three photons in a way not achievable with
independently created photon pairs. We expect our photon-triplet source to open
up new avenues of quantum optics and become an important tool in quantum
technologies. Our source will allow experimental interrogation of novel quantum
correlations, the post-selection free generation of tripartite entanglement
without post- selection and the generation of heralded entangled-photon pairs
suitable for linear optical quantum computing. Two of the triplet photons have
a wavelength matched for optimal transmission in optical fibres, ideally suited
for three-party quantum communication. Furthermore, our results open
interesting regimes of non-linear optics, as we observe spontaneous
down-conversion pumped by single photons, an interaction also highly relevant
to optical quantum computing.Comment: 7 pages, 3 figures, 1 table; accepted by Natur
Quantum Measurement Theory in Gravitational-Wave Detectors
The fast progress in improving the sensitivity of the gravitational-wave (GW)
detectors, we all have witnessed in the recent years, has propelled the
scientific community to the point, when quantum behaviour of such immense
measurement devices as kilometer-long interferometers starts to matter. The
time, when their sensitivity will be mainly limited by the quantum noise of
light is round the corner, and finding the ways to reduce it will become a
necessity. Therefore, the primary goal we pursued in this review was to
familiarize a broad spectrum of readers with the theory of quantum measurements
in the very form it finds application in the area of gravitational-wave
detection. We focus on how quantum noise arises in gravitational-wave
interferometers and what limitations it imposes on the achievable sensitivity.
We start from the very basic concepts and gradually advance to the general
linear quantum measurement theory and its application to the calculation of
quantum noise in the contemporary and planned interferometric detectors of
gravitational radiation of the first and second generation. Special attention
is paid to the concept of Standard Quantum Limit and the methods of its
surmounting.Comment: 147 pages, 46 figures, 1 table. Published in Living Reviews in
Relativit
Ghost Imaging in the Time Domain
International audienceGhost imaging is a novel technique that produces the image of an object by correlating the intensity of two light beams, neither of which independently carries information about the shape of the object1, 2. Ghost imaging has opened up new perspectives to obtain highly resolved images3, even in the presence of noise and turbulence4. Here, by exploiting the duality between light propagation in space and time5, we demonstrate the temporal analogue of ghost imaging. We use a conventional fast detector that does not see the temporal âobjectâ to be characterized and a slow integrating âbucketâ detector that does see the object but without resolving its temporal structure. Our experiments achieve temporal resolution at the picosecond level and are insensitive to the temporal distortion that may occur after the object. The approach is scalable, can be integrated on-chip, and offers great promise for dynamic imaging of ultrafast waveforms