Multi-photon Counting Research Articles

Sub-Nanosecond Digital Signal Processing of Photomultiplier Tube Response Enabling Multiphoton Counting in Raman Spectroscopy.

This paper introduces a novel approach to achieve multiple photon counting for Raman spectroscopy. The multiphoton counting process is made possible by recording and analyzing the photomultiplier tube response to each pulse of a pulsed laser in a time-resolved Raman spectroscopy system. Conventional Raman spectroscopy typically considers photon arrivals as binary events assessed by a single threshold. Hence, the conventional algorithm ignores the fact that multiple photons could arrive within the same response, sacrificing potential signal gain. In this work, a high-speed data acquisition system and multiple threshold digital signal processing counting algorithm are employed to facilitate multiphoton counting, a data processing approach that differentiates photon arrival events by amplitude and time and contributes to improved Raman detection sensitivity. The multiphoton counting algorithm enables lower concentration detection, greater sensitivity, shortens experiment duration, and improves noise rejection. Results from analyses of aqueous solutions of nitrate, isopropanol, and rhodamine 6G demonstrate the versatility and effectiveness of this algorithm. The algorithm increased system sensitivity by ∼ 2.0-, 2.0-, and 3.1-fold, compared to traditional single-threshold analyses of the same data for tests performed on nitrate, isopropanol, and rhodamine 6G, respectively. Results also demonstrated that the multiphoton counting algorithm increases the upper analysis limit for high Raman-yield compounds, shifting the saturation threshold to a higher concentration in typical concentration versus intensity calibration curves.

Generation of mechanical interference fringes by multi-photon counting

Exploring the quantum behaviour of macroscopic objects provides an intriguing avenue to study the foundations of physics and to develop a suite of quantum-enhanced technologies. One prominent path of study is provided by quantum optomechanics which utilizes the tools of quantum optics to control the motion of macroscopic mechanical resonators. Despite excellent recent progress, the preparation of mechanical quantum superposition states remains outstanding due to weak coupling and thermal decoherence. Here we present a novel optomechanical scheme that significantly relaxes these requirements allowing the preparation of quantum superposition states of motion of a mechanical resonator by exploiting the nonlinearity of multi-photon quantum measurements. Our method is capable of generating non-classical mechanical states without the need for strong single-photon coupling, is resilient against optical loss, and offers more favourable scaling against initial mechanical thermal occupation than existing schemes. Moreover, our approach allows the generation of larger superposition states by projecting the optical field onto NOON states. We experimentally demonstrate this multi-photon-counting technique on a mechanical thermal state in the classical limit and observe interference fringes in the mechanical position distribution that show phase super-resolution. This opens a feasible route to explore and exploit quantum phenomena at a macroscopic scale.

Prospects of in vivo singlet oxygen luminescence monitoring: Kinetics at different locations on living mice

BackgroundSinglet oxygen observation is considered a valuable tool to assess and optimize PDT treatment. In complex systems, such as tumors in vivo, only the direct, time-resolved singlet oxygen luminescence detection can give reliable information about generation and interaction of singlet oxygen. Up to now, evaluation of kinetics was not possible due to insufficient signal-to-noise ratio. Here we present high signal-to-noise ratio singlet oxygen luminescence kinetics obtained in mouse tumor model under PDT relevant conditions. MethodsA highly optimized system based on a custom made laser diode excitation source and a high aperture multi-furcated fiber, utilizing a photomultiplier tube with a multi photon counting device was used. ResultsLuminescence kinetics with unsurpassed signal-to-noise ratio were gained from tumor bearing nude mice in vivo upon topic application, subcutaneous injection as well as intravenous injection of different photosensitizers (chlorin e6 and dendrimer formulations of chlorin e6). Singlet oxygen kinetics in appropriate model systems are discussed to facilitate the interpretation of complex kinetics obtained from in vivo tumor tissue. ConclusionsThis is the first study addressing the complexity of singlet oxygen luminescence kinetics in tumor tissue. At present, further investigations are needed to fully explain the processes involved. Nevertheless, the high signal-to-noise ratio proves the applicability of direct time-resolved singlet oxygen luminescence detection as a prospective tool for monitoring photodynamic therapy.

High-fidelity spatially resolved multiphoton counting for quantum imaging applications.

We present a method for spatially resolved multiphoton counting based on an intensified camera with the retrieval of multimode photon statistics fully accounting for nonlinearities in the detection process. The scheme relies on one-time quantum tomographic calibration of the detector. Faithful, high-fidelity reconstruction of single- and two-mode statistics of multiphoton states is demonstrated for coherent states and their statistical mixtures. The results consistently exhibit classical values of the Mandel parameter and the noise reduction factor in contrast to raw statistics of camera photo-events. Detector operation is reliable for illumination levels up to the average of one detected photon per an event area-substantially higher than in previous approaches to characterize quantum statistical properties of light with spatial resolution.

Pulse-resolved multi-photon X-ray detection at 31 MHz based on a quadrant avalanche photodiode.

The technical realisation and the commissioning experiments of a high-speed X-ray detector based on a quadrant avalanche silicon photodiode and high-speed digitizers are described. The development is driven by the need for X-ray detectors dedicated to time-resolved diffraction and imaging experiments, ideally requiring pulse-resolved data processing at the synchrotron bunch repetition rate. By a novel multi-photon detection scheme, the exact number of X-ray photons within each X-ray pulse can be recorded. Commissioning experiments at beamlines P08 and P10 of the storage ring PETRA III, at DESY, Hamburg, Germany, have been used to validate the pulse-wise multi-photon counting scheme at bunch frequencies ≥ 31 MHz, enabling pulse-by-pulse readout during the PETRA III 240-bunch mode with single-photon detection capability. An X-ray flux of ≥ 3.7 × 10(9) photons s(-1) can be detected while still resolving individual photons at low count rates.

Development of techniques for characterisation of scintillation materials for cryogenic application

Abstract The multi-photon counting (MPC) technique was designed to record photon emission of scintillators and, as a very powerful method of material characterisation, is enjoying increasing popularity. The technique is especially advantageous for the analysis of slow scintillation processes and the investigation of temperature-dependent scintillator properties. The paper describes the latest development of the technique aiming to improve performance and widen the scope of applications. The results from characterising MgF 2 are presented to illustrate the capabilities of the MPC technique.

Scintillation studies of Bi 4Ge 3O 12 (BGO) down to a temperature of 6 K

The scintillation light response and the decay time constant of Bi 4Ge 3O 12 (BGO) were measured down to a temperature of 6 K using a multi-photon counting technique. The light response of BGO was confirmed to be temperature independent below 100 K and an estimate of the light yield was made, giving a value of 23,700±2600 ph/MeV. The temperature dependence of the scintillation decay time constant is interpreted using a simple three-level model for the emission centre which agrees well with the experimental data over the temperature range investigated.

Scintillation studies ofCaWO4in the millikelvin temperature range

We extended the multiphoton counting technique to investigate the scintillation characteristics of crystals at millikelvin temperatures using $^{3}\mathrm{He}∕^{4}\mathrm{He}$ dilution refrigerator. The temperature dependence of the scintillation time constant and the light response of $\mathrm{Ca}\mathrm{W}{\mathrm{O}}_{4}$ were measured down to $20\phantom{\rule{0.3em}{0ex}}\mathrm{mK}$. The scintillation light response is found to be independent of temperature below $10\phantom{\rule{0.3em}{0ex}}\mathrm{K}$---so far taken as an assumption in many cryogenic scintillator experiments, but yet previously unproved. The decay kinetics of $\mathrm{Ca}\mathrm{W}{\mathrm{O}}_{4}$ and its temperature dependence are analyzed in terms of a simple three-level model of the emission center. The model agrees well with the data over the temperature range $(0.02--350\phantom{\rule{0.3em}{0ex}}\mathrm{K})$ investigated, and is used to determine the parameters of the relaxed excited state.

Direct measurement of photon number statistics at telecom wavelengths using a charge integration photon detector

In optical quantum information technology, a photon number resolving detector (PNRD) is the basic device for developing photonic quantum computers. The demands for the PNRD are high quantum efficiency and wide dynamic range. We have developed a charge integration photon detector (CIPD) with a quantum efficiency of 80% at telecom wavelengths. The repetition rate of the CIPD is as low as 40 Hz at present, but it can be applied for measurement of short pulses. We report the capability of the CIPD for multiphoton counting over 10 photons, its responsivity to the short pulses, and its high linearity using a binary intensity modulated short pulse (2 ns) train and simultaneous irradiation of two kinds of pulses.

Multiple photon counting technique for detection and analysis of slow scintillation processes

The development of the multi-photon counting (MPC) technique for the investigation of scintillation properties of materials is presented. The technique is based on the recording and analysis of a sequence of individual photon pulses resulting from a scintillation event. The technique is especially advantageous for the analysis of slow scintillation processes and the investigation of temperature-dependent scintillator properties. The results on the temperature variation of scintillation characteristics of ZnSe and ZnSe–Te are presented to illustrate the performance of the MPC technique.

Optimization of multi-photon event discrimination levels using Poisson statistics

In applications where random multi-photon events must be distinguishable from the background, detection of the signals must be based on either analog current measurement or photon counting and multi-level discrimination of single and multi-photon events. In this paper a novel method for optimizing photomultiplier (PMT) pulse discrimination levels in single- and multi-photon counting is demonstrated. This calibration method is based on detection of photon events in coincidence to short laser pulses. The procedure takes advantage of Poisson statistics of single- and mult-iphoton signals and it is applicable to automatic calibration of photon counting devices on production line. Results obtained with a channel photomultiplier (CPM) are shown. By use of three parallel discriminators and setting the discriminator levels according to the described method resulted in a linear response over wide range of random single- and multi-photon signals.

Detailed analysis of the fidelity of quantum teleportation using photons: Considering real experimental parameters

In this paper we analyze the fidelity of the output states in the experimental quantum teleportation of photons, while taking into account the main experimental parameters. In particular, we consider the detector's ability to distinguish photon numbers, the quantum efficiency of the detectors, and the purity of entangled photon pairs. As a result, it is found that high-fidelity quantum teleportation, without the receiver feedback check, is realizable with multiphoton counters and conventional entangled pairs (visibility=90%) within a day.

Quantum key distribution using quantum-correlated photon sources

Quantum key exchanges using weak coherent (Poissonian) single-photon sources are open to attack by a variety of eavesdropping techniques. Quantum-correlated photon sources provide a means of flagging potentially insecure multiple-photon emissions and thus extending the secure quantum key channel capacity and the secure key distribution range. We present indicative photon-counting statistics for a fully correlated Poissonian multibeam photon source in which the transmitted beam is conditioned by photon number measurements on the remaining beams with non-ideal multiphoton counters. We show that significant rejection of insecure photon pulses from a twin-beam source cannot be obtained with a detector having a realistic quantum efficiency. However quantum-correlated (quadruplet or octuplet) multiplet photon sources conditioned by high efficiency multiphoton counters could provide large improvements in the secure channel capacity and the secure distribution range of high loss systems such as those using the low earth orbit satellite links proposed for global quantum key distribution.

Time-resolved multiphoton counting

A method for time-resolved detection of multiple fluorescence photons excited by low repetition laser pulses was developed and applied to radiophotoluminescent metaphosphate glass dosimeters.

On the multiphoton counting statistics of partially polarized chaotic light

We derive exact formulae and propose approximate formulae having good accuracy for the multiphoton counting statistics of partially polarized chaotic light of arbitrary spectrum.