32 research outputs found
Photon-number distributions of twin beams generated in spontaneous parametric down-conversion and measured by an intensified CCD camera
The measurement of photon-number statistics of fields composed of photon
pairs, generated in spontaneous parametric down-conversion and detected by an
intensified CCD camera is described. Final quantum detection efficiencies,
electronic noises, finite numbers of detector pixels, transverse intensity
spatial profiles of the detected beams as well as losses of single photons from
a pair are taken into account in a developed general theory of photon-number
detection. The measured data provided by an iCCD camera with single-photon
detection sensitivity are analyzed along the developed theory. Joint
signal-idler photon-number distributions are recovered using the reconstruction
method based on the principle of maximum likelihood. The range of applicability
of the method is discussed. The reconstructed joint signal-idler photon-number
distribution is compared with that obtained by a method that uses superposition
of signal and noise and minimizes photoelectron entropy. Statistics of the
reconstructed fields are identified to be multi-mode Gaussian. Elements of the
measured as well as the reconstructed joint signal-idler photon-number
distributions violate classical inequalities. Sub-shot-noise correlations in
the difference of the signal and idler photon numbers as well as partial
suppression of odd elements in the distribution of the sum of signal and idler
photon numbers are observed.Comment: 14 pages, 14 figure
Coherence properties of high-gain twin beams generated in pump-depletion regime
Twin-beam coherence properties are analyzed both in the spatial and spectral
domains at high-gain regime including pump depletion. The increase of the size
of intensity auto- and cross-correlation areas at increasing pump power is
replaced by a decrease in the pump depletion regime. This effect is interpreted
as a progressive loss in the mode selection occurring at high-gain
amplification. The experimental determination of the number of spatio-spectral
modes from -function measurements confirms this explanation.Comment: 7 pages, 7 figure
Multiple-photon resolving fiber-loop detector
We show first reconstructions of the photon-number distribution obtained with
a multi-channel fiber-loop detector. Apart from analyzing the statistics of
light pulses this device can serve as a sophisticated postselection device for
experiments in quantum optics and quantum information. We quantify its
efficiency by means of the Fisher information and compare it to the efficiency
of the ideal photodetector.Comment: 5 pages, 6 figure
Spectral structure and decompositions of optical states, and their applications
We discuss the spectral structure and decomposition of multi-photon states.
Ordinarily `multi-photon states' and `Fock states' are regarded as synonymous.
However, when the spectral degrees of freedom are included this is not the
case, and the class of `multi-photon' states is much broader than the class of
`Fock' states. We discuss the criteria for a state to be considered a Fock
state. We then address the decomposition of general multi-photon states into
bases of orthogonal eigenmodes, building on existing multi-mode theory, and
introduce an occupation number representation that provides an elegant
description of such states that in many situations simplifies calculations.
Finally we apply this technique to several example situations, which are highly
relevant for state of the art experiments. These include Hong-Ou-Mandel
interference, spectral filtering, finite bandwidth photo-detection, homodyne
detection and the conditional preparation of Schr\"odinger Kitten and Fock
states. Our techniques allow for very simple descriptions of each of these
examples.Comment: 12 page
Photon-number-resolving detectors for quantum-state engineering: introduction to the feature issue
Generation and measurement of quantum states of light represent a hot and widely discussed topic in the physical community for their possible applications to quantum optics and quantum information. To this aim, it is desirable that optical states are robust with respect to losses and can be produced and addressed at high rates. In fact, mesoscopic pulsed optical states containing few photons per pulse seem to be the ideal candidates for applications to quantum communication protocols. For all these reasons, during the last two decades many efforts have been devoted to the development of new kinds of detectors that can operate in such a photon-number-resolving domain
Spatial properties of twin-beam correlations at low-to high-intensity transition
It is shown that spatial correlation functions measured for correlated photon pairs at the single-photon level correspond to speckle patterns visible at high intensities. This correspondence is observed for the first time in one experimental setup by using different acquisition modes of an intensified CCD camera in low and high intensity regimes. The behavior of intensity auto-and cross-correlation functions in dependence on pumpbeam parameters including power and transverse profile is investigated