Photon Bunching Research Articles

Quantum Borrmann effect for dissipation-immune photon-photon correlations

We study theoretically the second-order correlation function $g^{(2)}(t)$ for photons transmitted through a periodic Bragg-spaced array of superconducting qubits, coupled to a waveguide. We demonstrate that photon bunching and anti-bunching persist much longer than both radiative and non-radiative lifetimes of a single qubit. The photon-photon correlations become immune to non-radiative dissipation due to the Borrmann effect, that is a strongly non-Markovian collective feature of light-qubit coupling inherent to the Bragg regime. This persistence of quantum correlations opens new avenues for enhancing the performance of setups of waveguide quantum electrodynamics.

Time- and frequency-domain two-particle correlations of a driven dissipative Bose-Hubbard model

We investigate theoretically the time- and frequency-domain two-particle correlations of a driven-dissipative Bose-Hubbard model at and near a dissipative phase transition (DPT). We compute the Hanbury Brown--Twiss (HBT)-type two-particle temporal correlation function ${g}^{2}(\ensuremath{\tau})$ which, as a function of time delay $\ensuremath{\tau}$, exhibits oscillations with frequencies determined by the imaginary part of the Liouvillian gap. As the gap closes near a transition point, the oscillations at that point die down. For parameters slightly away from the transition point, the HBT correlations show oscillations from superbunching to antibunching regimes. We show that the Fourier transform of HBT correlations into the frequency domain provide information about DPT and Liouvillian dynamics. We numerically solve the many-body Lindblad master equation and calculate the Wigner distribution of the system in the steady state to ascertain the DPT. Below a certain drive strength, the Fourier transform shows a two-peak structure, while above that strength it exhibits either a Lorentzian-like single-peak structure or a structure with two dips. The width of the single-peak structure is minimal at the phase-transition point and the peak of this structure always lies at zero frequency. The positions of the two symmetrical peaks in case of a two-peak structure are given by the imaginary parts of the Liouvillian gap while their half width at half maximum is given by the real part of the gap. The positions and widths of the two dips are also related to low-lying eigenvalues of the Liouvillian operator. We discuss quantum statistical properties of the model in terms of the HBT correlation function and its Fourier transform.

Detection of photon statistics and multimode field correlations by Raman processes.

Glauber's g(2)-function provides a common measure of quantum field statistics through two-photon coincidence counting in Hanbury Brown-Twiss measurements. Here, we propose to use nonlinear optical signals as a tool for the characterization of quantum light. In particular, we show that Raman measurements provide an alternative direct probe for a different component of the four-point correlation function underlying the g(2)-function. We illustrate this capacity for a specific quantum state obtained from a frequency conversion process. Our work points out how the analysis of controlled optical nonlinear processes can provide an alternative window toward the analysis of quantum light sources.

Microwave Communication Under Weak Intensity to Quantumized Level: Recent Progress and Future Challenges

We provide an overview of the recent progresses on the system architecture design and performance prediction for microwave signal detection under weak signal intensity regime, up to quantumized level. The technique roadmap includes two perspectives, the opto-electro-mechanical (OEM) and superconducting devices. For the former one, we first overview the concept of OEM, and then introduce the signal detection based on capacitive-opto-electro-mechanical systems and piezo- opto-electro-mechanical systems. For the latter one, we first overview the concept and architecture of Josephson junction, and then introduce the signal detection based on superconducting Hanbury Brown-Twiss (HBT) experiments and Λ energy-level splitting system. Besides, we review the microwave detection based on Rydberg atom system. We believe that this overview can provide a guidance for future transmission limit, signal processing, detection device fabrication and real experiments.

Photon Statistics of Incoherent Cathodoluminescence with Continuous and Pulsed Electron Beams

Photon bunching in incoherent cathodoluminescence (CL) spectroscopy originates from the fact that a single high-energy electron can generate multiple photons when interacting with a material, thus, revealing key properties of electron–matter excitation. Contrary to previous works based on Monte Carlo modeling, here we present a fully analytical model describing the amplitude and shape of the second order autocorrelation function (g(2)(τ)) for continuous and pulsed electron beams. Moreover, we extend the analysis of photon bunching to ultrashort electron pulses, in which up to 500 electrons per pulse excite the sample within a few picoseconds. We obtain a simple equation relating the bunching strength (g(2)(0)) to the electron beam current, emitter decay lifetime, pulse duration, in the case of pulsed electron beams, and electron excitation efficiency (γ), defined as the probability that an electron creates at least one interaction with the emitter. The analytical model shows good agreement with the experimental data obtained on InGaN/GaN quantum wells using continuous, ns-pulsed (using beam blanker) and ultrashort ps-pulsed (using photoemission) electron beams. We extract excitation efficiencies of 0.13 and 0.05 for 10 and 8 keV electron beams, respectively, and we observe that nonlinear effects play no compelling role, even after excitation with ultrashort and dense electron cascades in the quantum wells.

Photon bunching of the nonlinear photoluminescence emitted by plasmonics metals

In this report, we investigate the statistical temporal distribution of nonlinear upconverted photoluminescence emitted by gold and silver nanostructures excited by focused near-infrared laser pulses. We systematically observe a clear signature of photon bunching regardless of the nano-object’s geometry, material’s crystalline arrangement, and electronic band structure. The similarity of the data obtained across very different plasmonic objects confirms that these types of nonlinear radiation share a common chaotic origin and result from a collection of emitters. The correlation of photons at a picosecond time scale released by nanoscale nonlinear sources of broadband radiation may be used in plasmonic devices to develop new data temporal and spatial processing functionalities.

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.

CSHINE for studies of HBT correlation in heavy ion reactions

The compact spectrometer for heavy ion experiment (CSHINE) is under construction for the study of isospin chronology via the Hanbury Brown–Twiss (HBT) particle correlation function and the nuclear equation of state of asymmetrical nuclear matter. The CSHINE consists of silicon strip detector (SSD) telescopes and large-area parallel-plate avalanche counters, which measure the light charged particles and fission fragments, respectively. In phase I, two SSD telescopes were used to observe 30 MeV/u $$^{40}$$ Ar + $$^{197}$$ Au reactions. The results presented here demonstrate that hydrogen and helium were observed with high isotopic resolution, and the HBT correlation functions of light charged particles could be constructed from the obtained data.

Coulomb and strong interactions in the final state of Hanbury-Brown–Twiss correlations for Lévy-type source functions

We present detailed calculations about the expected shape of two-pion Bose-Einstein [or Hanbury-Brown--Twiss (HBT)] correlations in high energy heavy ion collisions that include a realistic treatment of final state Coulomb interaction as well as strong interactions (dominated by $s$-wave scattering). We assume L\'evy type source functions, a generalization that goes beyond the Gaussian approximation. Various recent experimental results found the use of such source types necessary to properly describe the shape of the measured correlation functions. We find that strong interaction effects for like-sign pions are small, but their consideration may become important in future precision measurements, especially if one considers source parameters beyond the Gaussian HBT radii. Precise experimental determination of these source parameters (such as L\'evy stability exponent, correlation strength, etc.) may then benefit from the inclusion of the treatment of strong interaction not just for heavier particles (e.g., protons, $\mathrm{\ensuremath{\Lambda}}\mathrm{s}$) but also in case of two-pion measurements.

Pion interferometry at 200 GeV using anisotropic hydrodynamics

In this paper, we continue our phenomenological studies of heavy-ion collisions using 3+1d anisotropic hydrodynamics (aHydro). In previous works, we compared quasiparticle aHydro (aHydroQP) with ALICE 2.76 TeV Pb-Pb and RHIC 200 GeV Au-Au collision results. At both energies, the agreement was quite good between aHydroQP and the experimental data for many observables. In this work, we present comparisons of the Hanbury Brown--Twiss (HBT) radii and their ratios determined using pi+ pi+ pairs produced in 200 GeV Au-Au collisions. We first present comparisons with STAR results for the HBT radii and their ratios. We then present comparisons with PHENIX results for the HBT radii and their ratios. In both cases, we find reasonable agreement between aHydroQP predictions and available experimental results for the ratios of HBT radii. At the level of the radii themselves, in some cases quantitative differences on the order of 10-20% remain, which deserve further study.

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

Stellar Speckle and Correlation Derived From Classical Wave Expansions for Spherical Antennas

Michelson phase and Hanbury Brown-Twiss intensity stellar interferometry require expressions for the first-and second-order correlation functions, respectively, of the fields radiated by stars in terms of their diameters and measured quasi-monochromatic wavelengths. Although our sun and most other stars are spherical in shape at optical wavelengths, previous determinations of speckle and correlation functions have modeled stars as circular disks rather than spheres because of the mathematical tools available for partially coherent fields on planar surfaces. However, with the incentive that most stars are indeed shaped like spheres and not disks, this article models a star as a spherical antenna composed of a random distribution of uncorrelated volume sources within a thin surface layer (photosphere). Working directly with the time-domain fields, a self-contained, straightforward, detailed derivation of speckle patterns and correlation functions is given based on a novel, angularly symmetric, spherical mode expansion with coefficients determined by the assumed Lambertian nature of the star's radiation and the uniform asymptotic behavior of the spherical Hankel functions. First-order spatially averaged and temporally averaged correlation functions are proven to be identical, and the normalized second-order correlation function is shown to equal one plus the square of the first-order correlation function. The direct time-domain approach reveals explicit expressions for the quasi-monochromatic wave-packet fields of stellar radiation as well as new criteria for the validity of the far-field approximation for the fields of incoherent sources that are much less restrictive than the Rayleigh-distance criterion for coherent sources.

Features of non-classical light during its interaction with atoms and semiconductor nano-systems

The interactions of a three-level atomic system with a single mode of quantized field is investigated analytically. The effect of coherent population trapping is demonstrated for an arbitrary initial quantum field state and the peculiarities of this regime in squeezed vacuum light are found. Mutual influence between atomic and field subsystems and their entanglement arising during the interaction is demonstrated. A significant change of the field state during the interaction is shown. The possibility of photon bunching and anti-bunching and the formation of a quantum field with non-Gaussian properties is found.

Hanbury Brown and Twiss effect in spatiotemporal domain.

Hanbury Brown and Twiss (HBT) effect has broad applications in optics and other branches of physics, and traditionally this effect is considered in pure spatial or temporal domain. Here we investigate the spatiotemporal HBT effect, extending this phenomenon from spatial or temporal to spatiotemporal domain. By assuming the Gaussian statistics of partially coherent spatiotemporal pulsed sources, we find the generalized analytical results for spatiotemporal HBT effect in the compact form, with the help of the matrix-optics method, which can consider the HBT effect in spatial and temporal domain simultaneously. Furthermore, for Gaussian Schell-model pulsed beams (GSMPBs) used as a spatiotemporal correlated source, we have obtained the generalized expression to calculate spatiotemporal HBT effect, which is useful for up to three-dimensional cases in any second-order linear dispersive medium. By taking a simple two-dimensional case and using air as an example of a linear dispersive medium, we numerically illustrate the properties of the spatiotemporal HBT effect by adjusting the spatial and temporal parameters of the GSMPB source, and reveal the influence of both the spatial and temporal parameters on the spatiotemporal HBT effect. This work paves the path towards the detailed study of HBT effect for a source containing spatiotemporal information with Gaussian statistics.

Strongly correlated photons with quantum feedback in a cascaded nanoscale double-cavity system

We characterize via the second-order correlation function the quantum correlations in the transmitted light in a two-cascaded-cavities system side-coupled to a common waveguide via bidirectional propagation. Adopting a full quantum master equation and standard input-output theory, we calculate the zero-time-delay second-order correlation function and identify clearly distinguished parameter regimes with the photon bunching and antibunching. Our numerical results clearly show that strong photon antibunching can be achieved in the cascaded double-cavity system without the need for extra modal-overlap-based coupling between the two cavities. Remarkably, this strong photon antibunching appears in the weak-coupling regime of cavity quantum electrodynamics. The photon antibunching properties can be manipulated by adjusting the propagation phase. In addition, we discuss the influences of the emitter-to-cavity coupling strength and the waveguide-to-cavity coupling rate on the photon antibunching. Also, the experimental feasibility of our proposal with the current photonic crystal technique is analyzed. This study offers an alternative way to generate the strongly antibunched photons, which may have applications in on-chip quantum information processing.

Effective Control of Photon Statistics from Electroluminescence by Fano-like Interference Effect.

The photon blockade induced by optical nonlinearity has been widely used to generate single-photon emission under optical driving in quantum optics. However, the same approach is difficult to achieve in electrically driven molecular junctions. Here we propose a scheme for tuning photon statistics via Fano-like interference effect in a system consisting of two molecules within one optical cavity. Under electrical pumping, a transition from photon bunching to antibunching takes place as a manifestation of the Fano-like interference. This effect persists even in the presence of the dipole-dipole interaction between molecules based on the parameters extracted from the experiments. Our proposal can be realized in current-carrying scanning tunneling microscope junctions.

Coherence time of a cold-atom laser below threshold.

We experimentally study the coherence time of a below-threshold Raman laser in which the gain medium is a gas of magneto-optically trapped atoms. The second-order optical coherence exhibits photon bunching with a correlation time that is varied by two orders of magnitude by controlling the gain. Results are in good agreement with a simple analytic model that suggests the effect is dominated by gain, rather than dispersion, in this system. Cavity ring-down measurements show the photon lifetime, related to the first-order coherence time, is also increased.

Correlating photons using the collective nonlinear response of atoms weakly coupled to an optical mode

Photons in a nonlinear medium can repel or attract each other, resulting in a strongly correlated quantum many-body system. Typically, such strongly correlated states of light arise from the extreme nonlinearity granted by quantum emitters that are strongly coupled to a photonic mode. However, in these approaches, unavoidable dissipation, like photon loss, blurs nonlinear quantum effects. Here, we generate strongly correlated photon states using only weak coupling and taking advantage of dissipation. We launch light through an ensemble of non-interacting waveguide-coupled atoms, which induce correlations between simultaneously arriving photons through collectively enhanced nonlinear interactions. These correlated photons then experience less dissipation than the uncorrelated ones. Depending on the number of atoms, we experimentally observe strong photon bunching or anti-bunching of the transmitted light. This realization of a collectively enhanced nonlinearity may turn out transformational for quantum information science and opens new avenues for generating nonclassical light, covering frequencies from the microwave to the X-ray regime.

Probing the evolution of heavy-ion collisions using direct photon interferometry

We investigate the measurement of Hanbury Brown-Twiss (HBT) photon correlations as an experimental tool to discriminate different sources of photon enhancement, which are proposed to simultaneously reproduce the direct photon yield and the azimuthal anisotropy measured in nuclear collisions at RHIC and the LHC. To showcase this, we consider two different scenarios in which we enhance the yields from standard hydrodynamical simulations. In the first, additional photons are produced from the early pre-equilibrium stage computed from the \textit{bottom-up} thermalization scenario. In the second, the thermal rates are enhanced close to the pseudo-critical temperature $T_c\approx 155\,\text{MeV}$ using a phenomenological ansatz. We compute the correlators for relative momenta $q_o, \,q_s$ and $q_l$ for different transverse pair momenta, $K_\perp$, and find that the longitudinal correlation is the most sensitive to different photon sources. Our results also demonstrate that including anisotropic pre-equilibrium rates enhances non-Gaussianities in the correlators, which can be quantified using the kurtosis of the correlators. Finally, we study the feasibility of measuring a direct photon HBT signal in the upcoming high-luminosity LHC runs. Considering only statistical uncertainties, we find that with the projected $\sim 10^{10}$ heavy ion events a measurement of the HBT correlations for $K_\perp<1\, \text{GeV}$ is statistically significant.

Pairing superbunching with compounded nonlinearity in a resonant transition

Through a quantitative analysis of an atomic transition driven strongly by quantized electromagnetic fields of various quantum states, we explore the role of quantum fluctuations on the behavior of the system. The emphasis is on fields with super-Poissonian statistics manifested in photon bunching, with the case of squeezed vacuum radiation serving as a prototype of superbuching. When combined with non-linearly coupling of the resonant states, bunching and superbunching lead to counter-intuitive behavior. The connection to recent progress in squeezed vacuum sources and the opportunity for experimental investigation, as well as challenging open theoretical problems are also outlined.