scholarly journals Photon Detection as a Process of Information Gain

Entropy ◽  
2020 ◽  
Vol 22 (4) ◽  
pp. 392 ◽  
Author(s):  
J Gerhard Müller

Making use of the equivalence between information and entropy, we have shown in a recent paper that particles moving with a kinetic energy ε carry potential information i p o t ( ε , T ) = 1 ln ( 2 ) ε k B T relative to a heat reservoir of temperature T . In this paper we build on this result and consider in more detail the process of information gain in photon detection. Considering photons of energy E p h and a photo-ionization detector operated at a temperature T D , we evaluate the signal-to-noise ratio S N ( E p h , T D ) for different detector designs and detector operation conditions and show that the information gain realized upon detection, i r e a l ( E p h , T D ) , always remains smaller than the potential information i p o t ( E p h , T D ) carried with the photons themselves, i.e.,: i r e a l ( E p h , T D ) = 1 ln ( 2 ) ln ( S N ( E p h , T D ) ) ≤ i p o t ( E p h , T D ) = 1 ln ( 2 ) E p h k B T D . This result is shown to be generally valid for all kinds of technical photon detectors, which shows that i p o t ( E p h , T D ) can indeed be regarded as an intrinsic information content that is carried with the photons themselves. Overall, our results suggest that photon detectors perform as thermodynamic engines that incompletely convert potential information into realized information with an efficiency that is limited by the second law of thermodynamics and the Landauer energy bounds on information gain and information erasure.

2020 ◽  
Vol 53 (3) ◽  
pp. 800-810
Author(s):  
Frank Heinrich ◽  
Paul A. Kienzle ◽  
David P. Hoogerheide ◽  
Mathias Lösche

A framework is applied to quantify information gain from neutron or X-ray reflectometry experiments [Treece, Kienzle, Hoogerheide, Majkrzak, Lösche & Heinrich (2019). J. Appl. Cryst. 52, 47–59], in an in-depth investigation into the design of scattering contrast in biological and soft-matter surface architectures. To focus the experimental design on regions of interest, the marginalization of the information gain with respect to a subset of model parameters describing the structure is implemented. Surface architectures of increasing complexity from a simple model system to a protein–lipid membrane complex are simulated. The information gain from virtual surface scattering experiments is quantified as a function of the scattering length density of molecular components of the architecture and the surrounding aqueous bulk solvent. It is concluded that the information gain is mostly determined by the local scattering contrast of a feature of interest with its immediate molecular environment, and experimental design should primarily focus on this region. The overall signal-to-noise ratio of the measured reflectivity modulates the information gain globally and is a second factor to be taken into consideration.


2010 ◽  
Vol 5 (01) ◽  
pp. P01002-P01002 ◽  
Author(s):  
C D R Azevedo ◽  
M Cortesi ◽  
A V Lyashenko ◽  
A Breskin ◽  
R Chechik ◽  
...  

2017 ◽  
Vol 24 (5) ◽  
pp. 1092-1097 ◽  
Author(s):  
Alberto Pietrini ◽  
Carl Nettelblad

The existence of noise and column-wise artifacts in the CSPAD-140K detector and in a module of the CSPAD-2.3M large camera, respectively, is reported for the L730 and L867 experiments performed at the CXI Instrument at the Linac Coherent Light Source (LCLS), in low-flux and low signal-to-noise ratio regime. Possible remedies are discussed and an additional step in the preprocessing of data is introduced, which consists of performing a median subtraction along the columns of the detector modules. Thus, we reduce the overall variation in the photon count distribution, lowering the mean false-positive photon detection rate by about 4% (from 5.57 × 10−5to 5.32 × 10−5 photon counts pixel−1frame−1in L867, cxi86715) and 7% (from 1.70 × 10-3to 1.58 × 10−3 photon counts pixel−1frame−1in L730, cxi73013), and the standard deviation in false-positive photon count per shot by 15% and 35%, while not making our average photon detection threshold more stringent. Such improvements in detector noise reduction and artifact removal constitute a step forward in the development of flash X-ray imaging techniques for high-resolution, low-signal and in serial nano-crystallography experiments at X-ray free-electron laser facilities.


2020 ◽  
pp. 28-35
Author(s):  
Alexei A. Samoylenko ◽  
Alexei D. Ivanov ◽  
Gennady G. Levin

Recent active development of quantum computers and quantum key distribution systems requires characterization of the parameters of single-photon detectors. A key parameter of single-photon detectors is detection efficiency. One of the methods for measuring the detection efficiency given in the international ETSI standard is the Klyshko reference-free method based on the use of the effect of spontaneous parametric downconversion. The signal-to-noise ratio (SNR) of this method depends on a combination of the pump wavelength, the nonlinear crystal axis angle, and the type of detector sensitive element. When the combination is complex, one has to deal with low SNR. In this case, to obtain a high SNR, long-term signal accumulation is necessary. In real detectors, the situation is complicated by the presence of a high noise level at low frequencies. The heterodyning-based method we have proposed consists in introducing modulation into the standard Klyshko scheme and accumulating the signal at a higher frequency. The method was numerically modeled and experimentally tested. A 14 times improvement in SNR was demonstrated compared to simple signal accumulation.


Author(s):  
Felix Greiffenhagen ◽  
Johannes Peterleithner ◽  
Jakob Woisetschläger

Modern gas turbines rely more and more on premixed combustion systems. While they produce less emission, they are more prone to combustion instabilities. The combustion noise emitted by turbulent swirl-stabilized flames can be calculated directly if density fluctuations in the flame are known as a function of time and space. Recently it was shown that laser interferometry records density fluctuations in the flame quantitatively. In this work a swirl-stabilized, rotationally-symmetric unconfined methane flame at lean operation conditions and low air mass flow rate was scanned by laser interferometric vibrometry (LIV) in order to calculate the overall sound power emitted by the flame. To validate the outcome calculated from the LIV data, sound power was also measured in a half-hemisphere by microphones, using pressure-pressure-probes. These probes record the total sound power of the combustion noise emitted by the flame. To improve signal to noise ratio for this measurement, a siren was used to generate a reproducible excitation of the flame at 212Hz. Both measurement methods were in good agreement. With the LIV data detailed information about the local density fluctuations in the flame causing the sound emission was obtained. Also a preferred acoustic propagation direction between 40° and 80° to the burner axis in downstream direction was observed. This deviation from a uniform distribution is likely to be caused by temperature gradients in the flame. A discussion of systematic errors inherent to the LIV technique and data reduction concludes this publication.


2018 ◽  
Vol 8 (9) ◽  
pp. 1652 ◽  
Author(s):  
Arne Josten ◽  
Benedikt Baeuerle ◽  
Romain Bonjour ◽  
Wolfgang Heni ◽  
Juerg Leuthold

An important challenge in optical communications is the generation of highest-quality waveforms with a Mach–Zehnder modulator with a limited electrical swing (Vpp). For this, we discuss, under limited Vpp, the influence of the waveform design on the root-mean-square amplitude, and thus, the optical signal quality. We discuss the influence of the pulse shape, clipping, and digital pre-distortion on the signal quality after the electrical-to-optical conversion. Our simulations and experiments, e.g., suggest that pre-distortion comes at the expense of electrical swing of the eye-opening and results in a lower optical signal-to-noise ratio (OSNR). Conversely, digital post-distortion provides operation with larger eye-openings, and therefore, provides an SNR increase of at least 0.5 dB. Furthermore, we find that increasing the roll-off factor increases the electrical swing of the eye-opening. However, there is negligible benefit of increasing the roll-off factor of square-root-raised-cosine pulse shaped signals beyond 0.4. The findings are of interest for single-channel intensity modulation and direct detection (IM/DD) links, as well as optical coherent communication links.


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