1,656 research outputs found
Experimental multi-photon-resolving detector using a single avalanche photodiode
A multichannel detector has been constructed using a single avalanche
photodiode and a fiber-loop delay line. Detection probabilities of the channels
can be set using a variable-ratio coupler. The performance of the detector is
demonstrated on its capability to distinguish multi-photon states (containing
two or more photons) from the one-photon state and the vacuum state.Comment: LATEX, 11 pages, 5 PostScript figure
Absolute detector calibration using twin beams
A method for the determination of absolute quantum detection efficiency is
suggested based on the measurement of photocount statistics of twin beams. The
measured histograms of joint signal-idler photocount statistics allow to
eliminate an additional noise superimposed on an ideal calibration field
composed of only photon pairs. This makes the method superior above other
approaches presently used. Twin beams are described using a paired variant of
quantum superposition of signal and noise.Comment: 3 pages, 2 figure
Magic in the spectra of the XXZ quantum chain with boundaries at Delta=0 and Delta=-1/2
We show that from the spectra of the U_q (sl(2)) symmetric XXZ spin-1/2
finite quantum chain at Delta=-1/2 (q=e^{pi i/3}) one can obtain the spectra of
certain XXZ quantum chains with diagonal and non-diagonal boundary conditions.
Similar observations are made for Delta=0 (q=e^{pi i/2}). In the finite-size
scaling limit the relations among the various spectra are the result of
identities satisfied by known character functions. For the finite chains the
origin of the remarkable spectral identities can be found in the representation
theory of one and two boundaries Temperley-Lieb algebras at exceptional points.
Inspired by these observations we have discovered other spectral identities
between chains with different boundary conditions.Comment: 29 page
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
The high voltage system for the novel MPGD-based photon detectors of COMPASS RICH-1
The architecture of the novel MPGD-based photon detectors of COMPASS RICH-1
consists in a large-size hybrid MPGD multilayer layout combining two layers of
Thick-GEMs and a bulk resistive MICROMEGAS. Concerning biasing voltage, the
Thick-GEMs are segmented in order to reduce the energy released in case of
occasional discharges, while the MICROMEGAS anode is segmented in pads
individually biased at positive voltage, while the micromesh is grounded. In
total, there are ten different electrode types and more than 20000 electrodes
supplied by more than 100 HV channels. Commercial power supply units are used.
The original elements of the power supply system are the architecture of the
voltage distribution net, the compensation, by voltage adjustment, of the
effects of pressure and temperature variation affecting the detector gain and a
sophisticated control software, which allows to protect the detectors against
errors by the operator, to monitor and log voltages and current at 1 Hz rate
and to automatically react to detector misbehaviors. The HV system and its
performance are described in detail as well as the electrical stability of the
detector during the operation at COMPASS.Comment: 5th international conference on Micro-Pattern Gas Detectors
(MPGD2017),presentation by Silvia Dalla Torr
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