Photon Bunching Effect Research Articles

Photon discerner: adaptive quantum optical sensing near the shot noise limit

Photon statistics of an optical field can be used for quantum optical sensing in low light level scenarios free of bulky optical components. However, photon-number-resolving detection to unravel the photon statistics is challenging. Here, we propose a novel detection approach, that we call ‘photon discerning’, which uses adaptive photon thresholding for photon statistical estimation without recording exact photon numbers. Our photon discerner is motivated by the field of neural networks where tunable thresholds have proven efficient for information extraction in machine learning tasks. The photon discerner maximizes Fisher information per photon by iteratively choosing the optimal threshold in real-time to approach the shot noise limit. Our proposed scheme of adaptive photon thresholding leads to unique remote-sensing applications of quantum degree of linear polarization camera and quantum LiDAR. We investigate optimal thresholds and show that the optimal photon threshold can be counter-intuitive (not equal to 1) even for weak signals (mean photon number much less than 1), due to the photon bunching effect. We also put forth a superconducting nanowire realization of the photon discerner which can be experimentally implemented in the near-term. We show that the adaptivity of our photon discerner enables it to beat realistic photon-number-resolving detectors with limited photon-number resolution in certain applications. Our work suggests a new class of detectors for information-theory driven, compact, and learning-based quantum optical sensing.

Properties of new even and odd nonlinear coherent states with different parameters

We construct a class of nonlinear coherent states (NLCSs) by introducing a more general nonlinear function and study their nonclassical properties, specifically the second-order correlation function [Formula: see text], Mandel parameter Q, squeezing, amplitude-squared squeezing and Wigner function of the optical field. The results indicate that the nonclassical properties of the new types of even and odd NLCSs crucially depend on the nonlinear functions. More concretely, we find that the new even NLCSs could exhibit the photon-bunching effect, whereas the new odd NLCSs could show the photon-antibunching effect. The degree of squeezing is also significantly affected by the parameter selection of these NLCSs. By employing various forms of nonlinear functions, it becomes possible to construct the NLCSs with diverse properties, thereby providing a theoretical foundation for the corresponding experimental investigations.

Investigation of the generalised Wigner–Dunkl harmonic oscillator and its coherent states

This study investigates the quantum mechanics of the harmonic oscillator in the presence of the Generalised-Wigner–Dunkl formalism based on creation and annihilation operators, which include also the reflection operator. We provide explicit results on the spectral properties of the Hamiltonian and an explicit form of the quantum propagator. Deformed coherent states are introduced and their non-classical properties such as photon statistics, Mandel parameter, and bunching or anti-bunching effect are studied.

Antibunching and superbunching photon correlations in pseudo-natural light

Since Hanbury Brown and Twiss revealed the photon bunching effect of a thermal light source in 1956, almost all studies in correlation optics have been based on light’s intensity fluctuation, regardless of fact that the polarization fluctuation is a basic attribute of natural light. In this work, we uncover the veil of the polarization fluctuation and corresponding photon correlations by proposing a new light source model, termed pseudo-natural light, embodying both intensity and polarization fluctuations. Unexpectedly, the strong antibunching and superbunching effects can be simultaneously realized in such a new source, whose second-order correlation coefficient g ( 2 ) can be continuously modulated across 1. For the symmetric Bernoulli distribution of the polarization fluctuation, particularly, g ( 2 ) can be in principle from 0 to unlimitedly large. In pseudo-natural light, while the bunching effects of both intensity and polarization fluctuations enhance the bunching to superbunching photon correlation, the antibunching correlation of the polarization fluctuation can also be extracted through the procedure of division operation in the experiment. The antibunching effect and the combination with the bunching one will arouse new applications in quantum imaging. As heuristic examples, we carry out high-quality positive or negative ghost imaging, and devise high-efficiency polarization-sensitive and edge-enhanced imaging. This work, therefore, sheds light on the development of multiple and broad correlation functions for natural light.

Coupled Colloidal Quantum Dot Molecules.

ConspectusElectronic coupling and hence hybridization of atoms serves as the basis for the rich properties for the endless library of naturally occurring molecules. Colloidal quantum dots (CQDs) manifesting quantum strong confinement possess atomic-like characteristics with s and p electronic levels, which popularized the notion of CQDs as artificial atoms. Continuing this analogy, when two atoms are close enough to form a molecule so that their orbitals start overlapping, the orbitals energies start to split into bonding and antibonding states made out of hybridized orbitals. The same concept is also applicable for two fused core–shell nanocrystals in close proximity. Their band edge states, which dictate the emitted photon energy, start to hybridize, changing their electronic and optical properties. Thus, an exciting direction of “artificial molecules” emerges, leading to a multitude of possibilities for creating a library of new hybrid nanostructures with novel optoelectronic properties with relevance toward diverse applications including quantum technologies.The controlled separation and the barrier height between two adjacent quantum dots are key variables for dictating the magnitude of the coupling energy of the confined wave functions. In the past, coupled double quantum dot architectures prepared by molecular beam epitaxy revealed a coupling energy of few millielectron volts, which limits the applications to mostly cryogenic operation. The realization of artificial quantum molecules with sufficient coupling energy detectable at room temperature calls for the use of colloidal semiconductor nanocrystal building blocks. Moreover, the tunable surface chemistry widely opens the predesigned attachment strategies as well as the solution processing ability of the prepared artificial molecules, making the colloidal nanocrystals as an ideal candidate for this purpose. Despite several approaches that demonstrated enabling of the coupled structures, a general and reproducible method applicable to a broad range of colloidal quantum materials is needed for systematic tailoring of the coupling strength based on a dictated barrierThis Account addresses the development of nanocrystal chemistry to create coupled colloidal quantum dot molecules and to study the controlled electronic coupling and their emergent properties. The simplest nanocrystal molecule, a homodimer formed from two core/shell nanocrystal monomers, in analogy to homonuclear diatomic molecules, serves as a model system. The shell material of the two CQDs is structurally fused, resulting in a continuous crystal. This lowers the potential energy barrier, enabling the hybridization of the electronic wave functions. The direct manifestation of the hybridization reflects on the band edge transition shifting toward lower energy and is clearly resolved at room temperature. The hybridization energy within the single homodimer molecule is strongly correlated with the extent of structural continuity, the delocalization of the exciton wave function, and the barrier thickness as calculated numerically. The hybridization impacts the emitted photon statistics manifesting faster radiative decay rate, photon bunching effect, and modified Auger recombination pathway compared to the monomer artificial atoms. Future perspectives for the nanocrystals chemistry paradigm are also highlighted.

Quantum Properties of Two-mode Squeezed Thermalized States

We have studied the statistical and squeezing properties of the Two-mode squeezed thermal light. We have calculated the mean of the photon number sum and difference, the variance of the photon number sum and difference, second order correlation function, the quadrature variance and quadrature squeezing, employing the Q function. We have found that the mean of the photon number sum for the two-mode squeezed thermal light is the sum of the means of the photon number sum of the separate modes and the photon statistic is super Poissonian. And the photon number of a two-mode squeezed thermal light is correlated and we have seen that the two-mode squeezed thermal light exhibiting the photon bunching effect. Moreover, the quadrature variance of the two-mode squeezed thermal light turns out to be the product of the quadrature variances of the two-mode thermal and two-mode squeezed vacuum states. The squeezing increase with increasing the squeeze parameter and with decreasing the mean photon number of thermal light. DOI: 10.7176/JNSR/11-23-01 Publication date: December 31 st 2020

Second-order correlation function of fluorescence from a few atoms near plasmonic surface

We have used a full quantum mechanical approach to study the second-order correlation function of a system of a few two-level atoms coupled via plasmons. By the usage of quantum regression theory we have developed a new model that allows us to fully investigate the dependence of photon bunching and anti-bunching effects to the interaction between atoms, fields and surrounding medium. Using Dicke basis for several atomic systems, we show that Dicke states can be coupled via various relaxation processes near plasmonic and metamaterial surfaces, and as a result, the second-order correlation function has various characteristic time scales related to the supperadiant and subradiant transitions and these prediction can be observed experimentally.

Multi-order quantum beating effect of three-photon temporal interference with nondegenerate fluorescence sources

The multi-order quantum beating effect of three-photon temporal interference generated by three nondegenerate fluorescence sources is studied. The third-order temporal correlation function of three nondegenerate photons results from the superposition of two-photon and three-photon bunching, multi-order quantum beating and temporal interference of three-photon. The simulate results show strong quantum beating and photon bunching behavior. The visibility of interference pattern, and the switching between photon bunching and beating effect can be modulated by the frequency difference, bandwidth of photons and the relative time delay of detectors. Such controllable coherent signal has potential applications as router and logic gate in quantum communication and information processing.

Observation of two-photon interference with continuous variables by homodyne detection

We experimentally observed a two-photon interference between a squeezed vacuum state from an optical parametric amplifier and a weak coherent state on a beam splitter with continuous variables. The photon statistics properties of the mixed field were investigated by calculating the correlations among four permutations of measured quadratures components, which were obtained by two homodyne detection systems. This also means that the two-photon interference occurred at analysis frequency differing from the previous two-photon interference reports. The nonclassical effect of photon anti-bunching occurred when an amplitude squeezed vacuum state acted as one of interference sources. On the other hand, the photon bunching effect appeared when a phase squeezed vacuum state was employed.

Direct observation of phase-sensitive Hong-Ou-Mandel interference

Quality of individual photons and their ability to interfere is traditionally tested by measuring the Hong-Ou-Mandel photon bunching effect. However, this phase insensitive measurement only tests the particle aspect of the quantum interference. Motivated by these limitations, we formulate a witness capable of recognizing both the quality and the coherence of two photons from a single set of measurements. We exploit the conditional nonclassical squeezing which is sensitive to both the quality of the single photons and their indistinguishability and we show that it can be used to irectly reveal both the particle and the wave aspects of the quantum interference. Finally, we experimentally test the witness by applying it to a pair of independent single photons generated on demand.

Bunching effect and quantum statistics of partially indistinguishable photons

The quantum statistics of particles is determined by both the spins and the indistinguishability of quantum states. Here we studied the quantum statistics of partially distinguishable photons by defining the multi-photon indistinguishability. The photon bunching co-efficient was formulated based on the properties of permutation symmetry, and a modified Bose--Einstein statistics was presented with an indistinguishability induced photon bunching effect. Moreover, the statistical transition of the photon state was studied for partially distinguishable photons, and the results shows the that indistinguishability exhibits the same role as that observed in the generation of laser. The results will fill the gap between Bose--Einstein and Poisson statistics for photons, and a formula is presented for the study of multi-photon quantum information processes.

Enhanced visibility of ghost imaging and interference using squeezed thermal light

Ghost imaging and interference using squeezed thermal light are investigated. We show that squeezed thermal light can have a very strong photon-bunching effect in the region of very weak squeezing and thermal excitation. As a result, the visibility of the image and interference pattern can be greatly enhanced and raised to be much higher than the limitation $1/3$ to thermal light. In the squeezed vacuum case, especially, the visibility can approach to the level of entangled photon pairs from spontaneous parametric down-conversion. The present investigation may open a new potential application of squeezed light.

Modal approach of photon correlations in lattices of coupled waveguides

Quantum propagation of indistinguishable photons in coupled waveguide lattices is analyzed in the asymptotic limit. Such an approach reveals the existence of two main relevant families of modes supported by the photonic lattice: localized side modes and Floquet-Bloch eigenmodes delocalized over the array. Under two-photon injection, the modal framework unravels the photon bunching and antibunching effects occurring in coupled waveguide lattices. In particular, photon correlations in the Floquet-Bloch modes are exhibited. Engineering of the propagation in such delocalized eigenmodes through patterning of the array coupling constant may open the way to discrete photonics platforms implementing efficient modal manipulation of quantum light involving large photon-number states.

Electromagnetically induced transparency in a Y system with single Rydberg state

We study the transmitted intensity and correlation properties of a probe field propagating through a sample of cold interacting 87Rb atoms driven into the Y level configuration with single Rydberg state. We find two electromagnetically induced transparency (EIT) windows in the transmission spectrum. One window is linear since it is immune to the incident probe field. The other window depth is sensitive to the incident probe intensity, exhibiting cooperative nonlinearity. Meanwhile, the linear window is low but the transmissivity at the nonlinear window can reach nearly 100% in case of the weak probe intensity. When two EIT windows overlap, the cooperative optical nonlinearity plays a leading role in the degenerate window. In addition, the probe propagation is affected by its two-photon correlation which is suppressed at the center of nonlinear window and is enhanced near the boundaries of two windows. The two-photon correlation is also sensitive to the probe field, and that means we can attain the strongest photon bunching (anti-bunching) effect by controlling the probe and coupling fields.

Generalized binomial distribution in photon statistics

Abstract The photon-number distribution between two parts of a given volume is found for an arbitrary photon statistics. This problem is related to the interaction of a light beam with a macroscopic device, for example a diaphragm, that separates the photon flux into two parts with known probabilities. To solve this problem, a Generalized Binomial Distribution (GBD) is derived that is applicable to an arbitrary photon statistics satisfying probability convolution equations. It is shown that if photons obey Poisson statistics then the GBD is reduced to the ordinary binomial distribution, whereas in the case of Bose- Einstein statistics the GBD is reduced to the Polya distribution. In this case, the photon spatial distribution depends on the phase-space volume occupied by the photons. This result involves a photon bunching effect, or collective behavior of photons that sharply differs from the behavior of classical particles. It is shown that the photon bunching effect looks similar to the quantum interference effect.

Electromagnetically induced transparency with cold Rydberg atoms: Superatom model beyond the weak-probe approximation

We present an improved superatom model for examining nonlinear optical responses of cold Rydberg atoms in the regime of electromagnetically induced transparency (EIT). By going beyond the weak-probe approximation, we find that several higher-order collective states should be included to correctly describe the coherent Rydberg excitation of superatoms. Otherwise, numerical results based on the simple ladder system of superatoms will contribute wrong predictions on light intensity and photon correlation of the transmitted probe field. In particular, a great photon-bunching effect will be improperly expected somewhere out of the EIT window in one dilute atomic sample. The essence of this improved superatom model lies in that it can provide reliable predictions on the nonlinear Rydberg-EIT phenomena even in dense atomic samples and may be extended to realize lossless conditional light interactions in appropriate multilevel systems exhibiting dipole blockade.

Photon emission statistics and photon tracking in single-molecule spectroscopy of molecular aggregates: Dimers and trimers

Based on the generating function formalism, we investigate broadband photon statistics of emission for single dimers and trimers driven by a continuous monochromatic laser field. In particular, we study the first and second moments of the emission statistics, which are the fluorescence excitation line shape and Mandel's Q parameter. Numerical results for this line shape and the Q parameter versus laser frequency in the limit of long measurement times are obtained. We show that in the limit of small Rabi frequencies and laser frequencies close to resonance with one of the one-exciton states, the results for the line shape and Q parameter reduce to those of a two-level monomer. For laser frequencies halfway the transition frequency of a two-exciton state, the photon bunching effect associated with two-photon absorption processes is observed. This super-Poissonian peak is characterized in terms of the ratio between the two-photon absorption line shape and the underlying two-level monomer line shapes. Upon increasing the Rabi frequency, the Q parameter shows a transition from super- to sub- to super-Poissonian statistics. Results of broadband photon statistics are also discussed in the context of a transition (frequency) resolved photon detection scheme, photon tracking, which provides a greater insight in the different physical processes that occur in the multi-level systems.

Highly efficient scheme for the implementation of optical controlled-Z gate via two-qubit polarization parity detector

A new scheme is proposed to direct implement the optical two-qubit controlled-Z gate with the two-qubit polarization parity detector [Lin, et al., Phys. Rev. A. 80 (2009) 042311] based on weak cross-Kerr nonlinearity. The distinct advantage of the present scheme in contrast with the existing schemes is that the two-qubit polarization parity detector with classical information feed-forward allows the efficiency of our optical controlled-Z gate to be enormously enhanced due to avoiding effectively the photon bunching effects. Therefore, the present scheme is more efficient and more convenient than others in the applications of quantum communication.

Photon statistics of squeezed vacuum field from optical parametric oscillator far below the threshold

Photon statistics of the weak squeezed vacuum field from an optical parametric oscillatior (OPO) is investigated both in theory and by experiment . The strong photon bunching effect of weak squeezed vacuum field, which can be used as an important source in quantum optics and quantum measurement, was demonstrated. We have experimentally produced the weak squeezed vacuum at the center wavelength of D2 line of the cesium atom by the OPO operating far below the threshold . The second-order correlation function was measured based on the Hanbury-Brown-Twiss scheme, and the result is consistent with theoretical analysis.

Two mode photon bunching effect as witness of quantum criticality in circuit QED

We suggest a scheme to probe critical phenomena at a quantum phase transition (QPT) using the quantum correlation of two photonic modes simultaneously coupled to a critical system. As an experimentally accessible physical implementation, a circuit QED system is formed by a capacitively coupled Josephson junction qubit array interacting with one superconducting transmission line resonator (TLR). It realizes an Ising chain in the transverse field (ICTF) which interacts with the two magnetic modes propagating in the TLR. We demonstrate that in the vicinity of criticality the originally independent fields tend to display photon bunching effects due to their interaction with the ICTF. Thus, the occurrence of the QPT is reflected by the quantum characteristics of the photonic fields.