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This work provides theoretical calculations of fluorescence angular distribution and polarization within an XUV pump–XUV probe scheme designed for determining ultra-short lifetimes of highly charged heavy ions. The initial pumping leads to a non-zero alignment in the excited levels. After the probing stage, the anisotropies in angular distribution and polarization of subsequent fluorescence are significantly enhanced due to the existence of a previous alignment. Furthermore, two-photon sequential excitation from a ground state with zero angular momentum to a level with angular momentum one by two aligned linearly polarized photon beams is strictly prohibited by the selection rules and may be used as a diagnostic tool to determine beam misalignment. The present approach is based on the density matrix and statistical tensor framework. We provide the analytical form for the alignment parameters caused by successive photoexcitation either with linearly polarized photon beams, or with unpolarized photons. The analytical results can generally be used to compute angular distribution asymmetry parameters and linear polarization of subsequent fluorescence for a large array of atomic systems used in pump–probe experiments. [ABSTRACT FROM AUTHOR]

The experiment on photodisintegration of tensor polarized deuteron is in progress. It is carried out at VEPP-3 storage ring using the internal polarized gas target technique. The component T20 of the tensor analyzing power is obtained by measuring the target polarization asymmetry in the photon energy range up to 1600MeV. The energy of photons is defined by the system that tags nearly real photons developed at the Budker Institute of Nuclear Physics (BINP). [ABSTRACT FROM AUTHOR]

The new version of the SANCphot integrator has been developed for fast and stable numerical calculations up to two loops for polarized light-by-light scattering. One-loop modules based on the helicity formalism with massive particles and two-loop modules with massless particles inside the loops are used. The presented study is driven by the potential of polarized photon beams to probe the high energy region. This study is a contribution to the research program of the CEPC project being under development in China. [ABSTRACT FROM AUTHOR]

We ask the question of how angular momentum is conserved in electroweak interaction processes. To introduce the problem with a minimum of mathematics, we first raise the same issue in elastic scattering of a circularly polarized photon by an atom, where the scattered photon has a different spin direction than the original photon, and note its presence in scattering of a fully relativistic spin-1/2 particle by a central potential. We then consider inverse beta decay in which an electron is emitted following the capture of a neutrino on a nucleus. While both the incident neutrino and final electron spins are antiparallel to their momenta, the final spin is in a different direction than that of the neutrino—an apparent change of angular momentum. However, prior to measurement of the final particle, in all these cases angular momentum is indeed conserved. The apparent nonconservation of angular momentum arises in the quantum measurement process in which the measuring apparatus does not have an initially welldefined angular momentum, but is localized in the outside world. We generalize the discussion to massive neutrinos and electrons, and examine nuclear beta decay and electron-positron annihilation processes through the same lens, enabling physically transparent derivations of angular and helicity distributions in these reactions. [ABSTRACT FROM AUTHOR]

Angle-resolved photoelectron spectrometers with microchannel plate detectors and fast digitizer electronics are versatile and powerful devices for providing non-invasive single-shot photon diagnostics at a MHz repetition rate X-ray free-electron lasers. In this contribution, we demonstrate and characterize the performance of our two operational photoelectron spectrometers for the application of hard X-rays and soft X-rays as well as new automation tools and online data analysis that enable continuous support for machine operators and instrument scientists. Customized software has been developed for the real-time monitoring of photon beam polarization and spectral distribution both in single-color and two-color operation. Hard X-ray operation imposes specific design challenges due to poor photoionization cross-sections and very high photoelectron velocities. Furthermore, recent advancements in machine learning enable resolution enhancement by training the photoelectron spectrometer together with an invasive high-resolution spectrometer, which generates a response function model. [ABSTRACT FROM AUTHOR]

A quantum mechanical approach to the psychoacoustic effect of Shepard tones has been explored. Melodic intervals are represented by qubits. The phenomenon of bistable perception of intervals and their acoustic collapse has been considered and described in the language of quantum mechanics. It is shown that the perception of intervals can be understood as a result of measuring the standard basis vector in different bases rotated in a plane of the chroma circle. For comparison, the Stern-Gerlach and photon polarization experiments have been cited to show an analogy. A quantum analog of the Shepard interval source, with a photonic random number generator, has been proposed. The topic of quantum entanglement transferred to the field of sound and psychoacoustics is also discussed. Based on quantum-like calculations, it has been shown how disturbances in time coherence between the playing of different music band members could affect the modification of the melody. [ABSTRACT FROM AUTHOR]

Research and curriculum development on quantum information science is a novel but technologically and socially significant challenge for physics education. While the debate is open on the core content, the approaches, and the strategies for addressing the need of effective instruction on the subject-matter, some indications have begun to emerge. Among them, the importance of an earlier start of education and of helping students develop not only a theoretical knowledge, but also high-level experimental skills including ideal design and conduction of experiments. Such skills are challenging to attain in existing traditional programs and may be considered inaccessible at introductory level because of the difficulties connected with qubit implementations. Here we present the design process, the structure, and a preliminary evaluation of a course for secondary school that is aimed to promote the building of a basic but integrated understanding of quantum information science, including experimental design and lab activities. The course was developed within the model of educational reconstruction, and embedded into a conceptual change framework in physics and computation. The encoding of polarization and which-path information of a photon is used to engage students in the development of a global model of logical encoding and processing, in ideal experimental design of gates and circuits, and in their implementation on the optical bench. Data show the effectiveness of the course in promoting student engagement in the modelling of gates in different encodings, in fostering an understanding of the computational role of physical setups, and a positive attitude and interest towards quantum computation and innovative teaching methods. [ABSTRACT FROM AUTHOR]

The first experimental observation of entangled visible light was achieved by optically exciting free atoms of calcium and detecting pairs of photons emitted in a two-stage cascade. The polarizations of the entangled photons were observed to be correlated, in agreement with quantum theory. This review describes the rationale, methodology, challenges, and results, including experimental details not previously published. [ABSTRACT FROM AUTHOR]

Spin-polarized light-emitting diodes (spin-LEDs) convert the electronic spin information to photon circular polarization, offering potential applications including spin amplification, optical communications, and advanced imaging. The conventional control of the emitted light's circular polarization requires a change in the external magnetic field, limiting the operation conditions of spin-LEDs. Here, we demonstrate an atomically thin spin-LED device based on a heterostructure of a monolayer WSe2 and a few-layer antiferromagnetic CrI3, separated by a thin hBN tunneling barrier. The CrI3 and hBN layers polarize the spin of the injected carriers into the WSe2. With the valley optical selection rule in the monolayer WSe2, the electroluminescence exhibits a high degree of circular polarization that follows the CrI3 magnetic states. Importantly, we show an efficient electrical tuning, including a sign reversal, of the electroluminescent circular polarization by applying an electrostatic field due to the electrical tunability of the few-layer CrI3 magnetization. Our results establish a platform to achieve on-demand operation of nanoscale spin-LED and electrical control of helicity for device applications. Spin-polarized light-emitting diodes (spin-LEDs) convert the electronic spin information to photon circular polarization, but they are usually controlled only by external magnetic fields. Here, the authors report the realization of spin-LEDs based on 2D CrI3/hBN/WSe2 heterostructures, showing electrical tunability of the electroluminescence helicity. [ABSTRACT FROM AUTHOR]

Motivated by recent advances in the development of single photon emitters for quantum information sciences, here we design and formulate a quantum cascade model that describes cascade emission by a quantum dot (QD) in a cavity structure while preserving entanglement that stores information needed for single photon emission. The theoretical approach is based on a photonic structure that consists of two orthogonal cavities in which resonance with either the first or second of the two emitted photons is possible, leading to amplification and rerouting of the entangled light. The cavity–QD scheme uses a four-level cascade emitter that involves three levels for each polarization, leading to two spatially entangled photons for each polarization. By solving the Schrodinger equation, we identify the characteristic properties of the system, which can be used in conjunction with optimization techniques to achieve the "best" design relative to a set of prioritized criteria or constraints in our optical system. The theoretical investigations include an analysis of emission spectra in addition to the joint spectral density profile, and the results demonstrate the ability of the cavities to act as frequency filters for the photons that make up the entanglements and to modify entanglement properties. The results provide new opportunities for the experimental design and engineering of on-demand single photon sources. [ABSTRACT FROM AUTHOR]

Ultracompact entangled photon sources are pivotal to miniaturized quantum photonic devices. Van der Waals (vdW) nonlinear crystals promise efficient photon-pair generation and on-chip monolithic integration with nanophotonic circuitry. However, it remains challenging to generate maximally entangled Bell states of photon pairs with high purity, generation rate, and fidelity required for practical applications. Here, we realize a polarization-entangled photon-pair source based on spontaneous parametric down conversion in an ultrathin rhombohedral tungsten disulfide (3R-WS2) crystal. This vdW entangled photonic source exhibits a high photon-pair purity with a coincidence-to-accidental ratio of above 800, a generation rate of 31 Hz, and two maximally polarization-entangled Bell states with fidelities exceeding 0.93 and entanglement degree over 0.97. These results stem from scalable optical nonlinearity, enhanced second-order susceptibility by electronic transitions, and a well-defined symmetry-enabled selection rule inherent in 3R-WS2. Our polarization entangled photon source can be integrated with photonic structures for generating more complex entangled states, thus paving an avenue for advanced quantum photonic systems toward computation and metrology. [ABSTRACT FROM AUTHOR]

Dichroic techniques are highly relevant in the field of topological materials, layered systems, and spin-polarized electronic states. Dichroism in angle-resolved photoemission is per se a matrix element effect, which depends on the initial and final states as well as on the perturbation by the light field. Although matrix element effects in ARPES such as dichroism are important for addressing properties of the initial state wave functions, the results can strongly depend on experimental geometry or final state effects. Combining experimental data on bulk WSe2 taken at soft x-ray photon energies with state-of-the-art photoemission calculations, we demonstrate that a dichroic observable called time-reversal dichroism remains unaffected against variation of photon energy, light polarization, and the angle of incidence. We demonstrate a direct link of TRDAD obtained with both linearly and circularly polarized photons to the initial state properties indicating its broad applicability. The robustness of this matrix element effect indicates a considerable benefit over other dichroic techniques and encourages further experimental and theoretical investigations. Matrix element effects in ARPES are important for addressing properties of the initial state wave functions, but the results can strongly vary with experimental configuration or final state. The authors show that an observable called time-reversal dichroism can filter out such effects, providing a direct link to orbital angular momentum and pseudospin. [ABSTRACT FROM AUTHOR]

In this review, we present a self-contained introduction to axion-like particles (ALPs) with a particular focus on their effects on photon polarization: both theoretical and phenomenological aspects are discussed. We derive the photon survival probability in the presence of photon–ALP interaction, the corresponding final photon degree of linear polarization, and the polarization angle in a wide energy interval. The presented results can be tested by current and planned missions such as IXPE (already operative), eXTP, XL-Calibur, NGXP, XPP in the X-ray band and like COSI (approved to launch), e-ASTROGAM, and AMEGO in the high-energy range. Specifically, we describe ALP-induced polarization effects on several astrophysical sources, such as galaxy clusters, blazars, and gamma-ray bursts, and we discuss their real detectability. In particular, galaxy clusters appear as very good observational targets in this respect. Moreover, in the very-high-energy (VHE) band, we discuss a peculiar ALP signature in photon polarization, in principle capable of proving the ALP existence. Unfortunately, present technologies cannot detect photon polarization up to such high energies, but the observational capability of the latter ALP signature in the VHE band could represent an interesting challenge for the future. As a matter of fact, the aim of this review is to show new ways to make progress in the physics of ALPs, thanks to their effects on photon polarization, a topic that has aroused less interest in the past, but which is now timely with the advent of many new polarimetric missions. [ABSTRACT FROM AUTHOR]

Circularly polarized luminescence (CPL)‐active materials are increasingly recognized for their potential applications such as 3D imaging, data storage, and optoelectronic devices. Typically, CPL materials have required high‐energy (HE) photons for excitation to emit low‐energy (LE) circularly polarized light, a process known as downshifting CPL (DSCPL). However, the emergence of upconverted CPL (UCCPL), where the absorption of multi LE photons results in the emission of a single HE photon with circular polarization, has recently attracted considerable attention. This minireview highlights the intricate relationship between upconversion and CPL phenomena. During upconversion, the dissymmetry factor (glum) value can be improved in certain systems. Additionally, the integration of both LE and HE photons in upconversion‐downshifting‐synergistic systems offers avenues for dual‐excitation or dual‐emission CPL functionalities. More in detail, the emerging UCCPL based on various photon upconversion mechanisms and their synergy with DSCPL are introduced. Additionally, several examples that demonstrate the applications of UCCPL are presented to highlight the future opportunities. [ABSTRACT FROM AUTHOR]

As a typical penta two-dimensional material and proposed to be potentially synthesized, in this paper we built a two-probe photodetector based on the penta-BP5 monolayer, and further studied linear and elliptical photogalvanic effects in this device. It was found that produced photocurrents in the BP5 photodetectors mainly show sine relation on double times of the polarized or elliptical angle for the incident light, and the relation can be modulated by the photon energy and polarized angle. Interestingly, due to high asymmetry of the BP5 monolayer, the pristine BP5 photodetector generates very high photocurrents, which are even larger than those including vacancy- and substitution-doping, and this result further proved that asymmetry plays a decisive role in the generation of robust photogalvanic effects, instead of introducing impurities to enhance this effect. Furthermore, the linear photogalvanic effect is stronger than the elliptical photogalvanic effect, and the BP5 photodetectors for the pristine, vacancy- and substitution-doping cases have relatively high extinction ratios showing these BP5 photodetectors are all polarization-sensitive. In conclude, these results manifest great potential applications of the penta-BP5 photodetectors on high performance optoelectronics and nanoelectronic devices. [ABSTRACT FROM AUTHOR]

A novel allotrope structure of carbon named twin irida graphene composed of 3‐16‐8 carbon rings is proposed. Its structural, mechanical, electronic, and optical characteristics are explored by density functional theory. It is shown that twin irida graphene has an energetically favorable structure. Its dynamical and thermal stabilities at room temperature are also examined and confirmed. The in‐plane stiffness of twin irida graphene is less than graphene. It is a metal and maintains this property even against the external strain and applied electric field. This sheet exhibits an anisotropy response to the incident photon with different polarizations. The potential of sheet for use in energy storage and absorption systems is indicated by its high dielectric constant and optical absorption. The reflection constants as well as the transmission constants of twin irida graphene indicate its transparency, mostly in the high‐energy region. Thus, twin irida graphene is a suitable material for use in optoelectronic applications due to its structural and physical characteristics. [ABSTRACT FROM AUTHOR]

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Room temperature quantum emitters have been reported in aluminum nitride grown on sapphire, but until now they have not been observed in epilayers grown on silicon. We report that epitaxial aluminum nitride grown on silicon by either plasma vapor deposition or metal-organic vapor phase epitaxy contains point-like emitters in the red to near-infrared part of the spectrum. We study the photon statistics and polarization of emission at a wavelength of 700–750 nm, showing signatures of quantized electronic states under pulsed and CW optical excitation. The discovery of quantum emitters in a material deposited directly on silicon can drive integration using industry standard 300 mm wafers, established complementary metal-oxide-semiconductor control electronics, and low marginal-cost mass-manufacturing. [ABSTRACT FROM AUTHOR]

The formation of e± plasmas within pulsar magnetospheres through quantum electrodynamics (QED) cascades in vacuum gaps is widely acknowledged. This paper aims to investigate the effect of photon polarization during the QED cascade occurring over the polar cap of a pulsar. We employ a Monte Carlo-based QED algorithm that accurately accounts for both spin and polarization effects during photon emission and pair production in both single-particle and particle-in-cell (PIC) simulations. Our findings reveal distinctive properties in the photon polarization of curvature radiation (CR) and synchrotron radiation (SR). CR photons exhibit high linear polarization parallel to the plane of the curved magnetic field lines, whereas SR photons, on average, demonstrate weak polarization. As the QED cascade progresses, SR photons gradually dominate over CR photons, thus reducing the average degree of photon polarization. Additionally, our study highlights an intriguing observation: the polarization of CR photons enhances e± pair production by approximately 5 per cent, in contrast to the inhibition observed in laser–plasma interactions. Our self-consistent QED-PIC simulations in the corotating frame reproduce the essential results obtained from single-particle simulations. [ABSTRACT FROM AUTHOR]

A theoretical study is performed for the single-photon creation of an electron–positron pair in an external magnetic field. We present general expressions for process rates that are valid for arbitrarily high field strengths. Simple analytical expressions are obtained in the limiting cases of weak and strong fields. The emphasis is placed on the investigation of the spin alignment of the created particles as a function of the incident photon polarization and magnetic field strength. The obtained results show that the maximum value of the polarization degree of electrons (positrons) decreases in supercritical magnetic field. [ABSTRACT FROM AUTHOR]

High-brilliance high-polarization γ rays based on Compton scattering are of great significance in broad areas, such as nuclear physics, high-energy physics, astrophysics, etc. However, the transfer mechanism of spin angular momentum in the transition from linear through weakly into strongly nonlinear processes is still unclear, which severely limits the simultaneous control of brilliance and polarization of high-energy γ rays. In this work, we clarify the transfer mechanism in the transition regions and put forward a clear way to efficiently manipulate the polarization of emitted photons. We find that to simultaneously generate high-energy, high-brilliance, and high-polarization γ rays, it is better to increase the laser intensity for the initially spin-polarized electron beam. However, for the case of employing the initially spin-nonpolarized electron beam, in addition to increasing laser intensity, it is also necessary to increase the energy of the electron beam. Because the γ photon polarization emitted through the single-photon absorption channel is mainly attributed to the spin transfer of laser photons, while in multi-photon absorption channels, the electron spin plays a major role. Moreover, we confirm that the signature of γ-ray polarization can be applied to observing the nonlinear effects (multi-photon absorption) of Compton scattering with moderate-intensity laser facilities. [ABSTRACT FROM AUTHOR]

Although water is almost transparent to visible light, we demonstrate that the air--water interface interacts strongly with visible light via what we hypothesize as the photomolecular effect. In this effect, transverse- magnetic polarized photons cleave off water clusters from the air--water interface. We use 14 different experiments to demonstrate the existence of this effect and its dependence on the wavelength, incident angle, and polarization of visible light. We further demonstrate that visible light heats up thin fogs, suggesting that this process can impact weather, climate, and the earth's water cycle and that it provides a mechanism to resolve the long- standing puzzle of larger measured clouds absorption to solar radiation than theory could predict based on bulk water optical constants. Our study suggests that the photomolecular effect should happen widely in nature, from clouds to fogs, ocean to soil surfaces, and plant transpiration and can also lead to applications in energy and clean water. [ABSTRACT FROM AUTHOR]

Single-layer transition-metal dichalcogenides provide an unique intrinsic entanglement between the spin/valley/orbital degrees of freedom and the polarization of scattered photons. This scenario gives rise to the well-assessed optical dichroism observed by using both steady and time-resolved probes. In this paper, we provide compact analytical modeling of the onset of a finite Faraday/Kerr optical rotation upon shining with circularly polarized light. We identify different optical features displaying optical rotation at different characteristic energies, and we describe in an analytical framework the time-dependence of their intensities as a consequence of the main spin-conserving and spin-flip processes. [ABSTRACT FROM AUTHOR]

The photogalvanic effect has been demonstrated to be an effective method to generate pure spin current. However, obtaining robust pure spin current remains a big challenge as most of the photo-induced pure spin current is dependent on the light polarization/phase angle, photon energies, or the spin alignment of electrodes. In this paper, we present a scheme for obtaining robust pure spin current in zigzag graphene–graphane superlattices (ZGSLs). Through systemic first-principles calculations, we demonstrate that robust generation of pure spin current can occur in ZGSLs with varying widths due to the centrosymmetry of the system's geometric structure and the antiferromagnetic magnetic features. Moreover, the generation of pure spin current does not depend on the photon energy or the polarization/phase angles for both linearly and elliptically polarized light, exhibiting very strong robustness. Our study suggests that ZGSLs could be highly promising candidates for practically realizing pure spin current in spintronics experiments, which presents an avenue for using graphene and its derivatives in advanced electronic devices. Furthermore, considering the experimental advancements in graphene and graphene-like materials, our investigation presents a universally applicable methodology for the generation of robust pure spin currents within low-dimensional graphene-like systems. [ABSTRACT FROM AUTHOR]

Entanglement purification is an important and useful tool in quantum communications that allows parties to enhance the entanglement of a set of less-entangled particles using local operations and classical communication. Utilizing photon polarization parity checks implemented through the coupling system between a single-sided cavity and a charged quantum dot, an entanglement purification scheme is proposed in this paper. The fidelity and the success probability of the scheme are calculated under bit-flip error channel and depolarizing channel, respectively. Furthermore, the impact of imperfect quantum-dot-cavity coupling system is investigated, and the feasibility is discussed. In the strong coupling and weak cavity side leakage regime, our scheme can approach the maximal fidelities and success probabilities in theory. So the scheme has potential applications in long-distance quantum communication with the development of relevant technologies. [ABSTRACT FROM AUTHOR]

This paper puts forward a novel quantum dialogue (QD) protocol without information leakage based on single photons in both polarization and spatial-mode degrees of freedom. In this protocol, the receiver sends his private message to the sender in the way of quantum secure direct communication; and the receiver decodes out the private message of the sender with the help of auxiliary single photons in two degrees of freedom, double controlled-not (CNOT) operations and an auxiliary classical bit sequence sent from the sender. As a result, no information leakage takes place. Moreover, this protocol is proven to defeat the intercept-resend attack, the measure-resend attack, the entangle-measure attack and the Trojan horse attack from an outside eavesdropper. This protocol only employs single photons in two degrees of freedom as quantum resource and needs single-photon measurements. The qubit efficiency of this protocol is as high as 66.7%. [ABSTRACT FROM AUTHOR]

2D materials have important fundamental properties allowing for their use in many potential applications, including quantum computing. Various Van der Waals materials, including Tungsten disulfide (WS2), have been employed to showcase attractive device applications such as light emitting diodes, lasers and optical modulators. To maximize the utility and value of integrated quantum photonics, the wavelength, polarization and intensity of the photons from a quantum emission (QE) must be stable. However, random variation of emission energy, caused by the inhomogeneity in the local environment, is a major challenge for all solid-state single photon emitters. In this work, we assess the random nature of the quantum fluctuations, and we present time series forecasting deep learning models to analyse and predict QE fluctuations for the first time. Our trained models can roughly follow the actual trend of the data and, under certain data processing conditions, can predict peaks and dips of the fluctuations. The ability to anticipate these fluctuations will allow physicists to harness quantum fluctuation characteristics to develop novel scientific advances in quantum computing that will greatly benefit quantum technologies. [ABSTRACT FROM AUTHOR]

The polarization of recoil photon ( γ ′ ) in the nonlinear Compton process e + L → → γ → ′ + e ′ in the interaction of a relativistic electron with a linearly polarized laser beam ( L → ) is studied within the Furry picture in the lowest order, tree-level S matrix element. In particular, we consider the asymmetry of differential cross sections A for two independent axes describing the Compton process equal to the intrinsic spin variable ξ 3 f that determines the polarization properties of γ ′ . The sign and absolute value of the asymmetry determine the direction and degree of γ ′ polarization. We have analyzed the process in a wide range of laser intensity that covers existing and future experiments. Our results provide additional knowledge for studying nonlinear multi-photon effects in quantum electrodynamics and can be used in planning experiments at envisaged laser facilities. [ABSTRACT FROM AUTHOR]

Birefringence, quantified as the maximum effective index difference of two orthogonally polarized modes, is one of the key characteristics of Lithium Niobate on Insulator (LNOI) waveguide devices. As LNOI optical properties strongly depend on the polarization of the propagating light beam, achieving the zero‐birefringence condition (ZBC) is highly desired. In this work, a rib LNOI waveguide is designed, and the influence of geometrical dimensions on the birefringence is characterized. From the result, the slab's height is found to be the dominant geometrical factor that significantly contributes to the birefringence, with an optimum slab's height found at 50 nm. For this optimized value, the influence of width and wavelength on birefringence are characterized. The analysis is extended to investigate the properties of group indices that can result in the temporal walk‐off phenomenon. This phenomenon can significantly impact the performance of single‐photon devices, as it can cause a polarization mismatch between the incident photon and the polarization properties of the medium, resulting in reduced efficiency of devices such as single‐photon detectors. In the analysis, the zero birefringence and walk‐off are achieved at narrow waveguide width, 푤 of 250 nm and wavelength, λ${\mathrm{\lambda }}$ = 1500 nm, which is within the telecommunication region band. [ABSTRACT FROM AUTHOR]

In the present work a computational approach is applied to model and predict the results of X‐ray resonant magnetic reflectometry – a non‐destructive synchrotron‐based technique to probe chemical composition, crystallographic environment and magnetization in multilayer epitaxial heterostructures with nanoscale depth resolution. The discussed 2D mapping approach is a step forward with respect to conventional resonant X‐ray reflectometry and consists of collecting a fine step array of reflected intensity as a function of grazing angle and photon energy across the absorption edge of a particular chemical element. With the use of circularly polarized photons the method can be extended to magnetic systems to produce a map of dichroic reflectance directly related to the magnetization profile of the heterostructure. Studying the magnetic field dependence of dichroic reflectance maps can provide valuable information on the magnetization reversal of individual sublayers of a multilayer heterostructure. In the present paper modeling is performed for a bilayer system mimicking the behavior of a 30 nm ϵ‐Fe2O3 thin film that is known to exhibit a pronounced two‐component magnetic hysteresis. A technique to find optimal energy/angle combinations in order to sense magnetization of individual sublayers is proposed. Also discussed is the advantage of heavy‐element capping, which leads to a substantial increase of the dichroic intensity oscillation contrast in the pre‐edge region where the sensitivity to the magnetic behavior of the deeply buried interfaces is most pronounced. [ABSTRACT FROM AUTHOR]

We report on IXPE, NICER, and XMM–Newton observations of the magnetar 1E 2259+586. We find that the source is significantly polarized at about or above 20  per cent for all phases except for the secondary peak where it is more weakly polarized. The polarization degree is strongest during the primary minimum which is also the phase where an absorption feature has been identified previously. The polarization angle of the photons are consistent with a rotating vector model with a mode switch between the primary minimum and the rest of the rotation of the neutron star. We propose a scenario in which the emission at the source is weakly polarized (as in a condensed surface) and, as the radiation passes through a plasma arch, resonant cyclotron scattering off of protons produces the observed polarized radiation. This confirms the magnetar nature of the source with a surface field greater than about 1015 G. [ABSTRACT FROM AUTHOR]

Integrated hierarchical microstructures composed of organic micro/nanocrystals with defined morphology have received great interest as candidates for advanced photonic circuits. Herein, the synthesis of highly ordered multilevel homogenous hyperbranched networks (HHNs) made of the individual organic compound 2, 3‐dicyanine naphthalene via a facile solution self‐assembly route is reported. The selective growth of branches on the sidewall of the backbone driven by the lattice match mechanism leads to the formation of higher‐level snowflake‐like configuration of the HHNs. These well‐organized HHNs perform excellent abilities of directional asymmetry photon transport and hierarchical polarization filtering. Combined with the doping strategy, the broad emission range of hyperbranched network heterostructures is expanded, and even the white light emission with Commission Internationale de L'Eclairage coordinates at (0.30, 0.33) is realized. This work provides deep insight into the rational creation of complex organic heterostructures for novel photoelectric devices with desired performances. [ABSTRACT FROM AUTHOR]

Unitarity and the optical theorem are used to derive the reduced density matrices of Compton scattering in the presence of a witness particle. Two photons are initially entangled wherein one photon participates in Compton scattering, while the other is a witness, i.e., does not interact with the electron. Unitarity is shown to require that the entanglement entropy of the witness photon does not change after its entangled partner undergoes scattering. The final mutual information of the electron's and witness particle's polarizations is shown to be nonzero for low-energy Compton scattering. This indicates that the two particles became correlated in spite of no direct interaction. Assuming an initial maximally entangled state, the change in entanglement entropy of the scattered photon's polarization is calculated in terms of Stokes parameters. A common ratio of areas occurs in the final reduced density matrix elements, von Neumann entropies, Stokes parameter, and mutual information. This common ratio consists of the Thomson scattering cross-section and an accessible regularized scattering area. [ABSTRACT FROM AUTHOR]

The defect of the angular momentum of an electron under cyclotron (synchrotron) radiation, including in terms of its spatial orientation, as well as the spatial orientation of the emitted photon, is considered. The possibility of the compatibility of the idea of the photon as a gauge boson, which can exist only in two spin states, ±1, with a linearly polarized photon, i.e., having no spin, has been studied. It is established that photons have no spin. The angular momentum defect can carry away a spinless photon. As applied to the angular momentum defect, the photon momentum arm is equal to its reduced wavelength. [ABSTRACT FROM AUTHOR]

We present here a model-independent theoretical discussion of differential cross-sections in photodisintegration of lithium with unpolarized and linearly polarized photons. In recent years, experimental measurements are being carried out on the photodisintegration of lithium in the reaction channel 7Li(γ, n)6Li to study the angular dependence of cross-section. In this regard, we have studied the spin structure of amplitudes in 7Li(γ, n)6Li by expressing the differential cross-section in terms of Legendre polynomials. [ABSTRACT FROM AUTHOR]

Structured photons are a crucial resource in both classical and quantum technologies, particularly in spin–orbit hybrid photons, enabling various practical applications ranging from ultra-sensitive metrology techniques to quantum-enhanced information processing tasks. However, the two-photon interference of spin–orbit hybrid photons, which combines polarization modes and complex transverse spatial structures across the beam profile, remains unexplored. Here, we present an experimental observation of Hong–Ou–Mandel (HOM) interference of spin–orbit hybrid photons. The tunable q-plates that work as spin–orbit coupler devices are used to prepare various forms of spin–orbit hybrid entangled photons. By harnessing the match degree in the temporal domain, the coalescence and anti-coalescence effects resulting from the symmetric and anti-symmetric properties of the incident quantum states are observed. Moreover, we demonstrated the feasibility of quantum-enhanced photon polarization gears through HOM interference and theoretically analyze the noise-resilient advantages based on coherent HOM measurements. These results provide an alternative route toward quantum experiments with structured photons that allows for controlling their quantum interference in a compact, stable, and efficient way. [ABSTRACT FROM AUTHOR]

Controlled activation of the polarization of single photon emitters is a challenge. We use CdSe/CdS dot-in-rods (DRs) confined and oriented in smectic topological grain boundaries to activate the fluorescence polarization through temperature variation. We show that temperature acts as a knob to switch on/off the polarization of DR emitted light between smectic and isotropic phase. This occurs through the orientational motion of the DR assemblies, which is induced in isotropic phase due to the disappearing of the defects. In addition, we evidence a significant improvement of DR emitted light polarization after cooling back from the isotropic phase. It is measured by the increase in polarization degree from 0.28 to 0.36 on average for DR assemblies. This improvement is managed by the smectic phase diagram near the smectic/nematic transition. Near the smectic/nematic transition, the smectic grain boundaries entirely cover the sample surface and allow for a reorientation of all DRs, even of those initially not confined in smectic grain boundaries. [ABSTRACT FROM AUTHOR]

We performed measurements of laser beam power polarized in different angles as 0 ∘ , 45 ∘ and 90 ∘ passing close to a symmetric shielded capacitor with parallel plates and through a polaroid filter configured with angles as 0 ∘ , 45 ∘ and 90 ∘ . An unusual light power variation was detected during the charging and discharging of the high voltage capacitor even considering the suppression of known electromagnetic interaction between laser beam and capacitor. The light power variation curves also indicated a typical pattern of charge and discharge of capacitors. The combination of the angles of the laser beam polarization and polaroid filter surprisingly indicated the measurement of correlations between the polarizations of photons and electric dipoles of the capacitor dielectric. These novel results can only be explained supposing the preexisting condition of quantum entanglements between discrete observables of electric dipoles and photons. [ABSTRACT FROM AUTHOR]

The Young's single- and double-slit experiments are explained using six-component quantum and one-component quasi-classical photon wave functions in the coordinate representation, which are modeled by different mechanisms of photon diffraction on slits or simultaneous emission of two photons by (two) independent sources. This explanation is compared with the well-known statement about the interference of a particle with itself when passing through both slits simultaneously in the Young's experiment on the basis of the postulated Feynman amplitudes. It is argued that these amplitudes cannot be wave functions, in the literal sense, describing some states of quantum particles. In all cases, under the assumption of the linear polarization of photons, a pronounced interference pattern has been obtained, which suggests that the coordinate wave function of a photon can explain the phenomena of the one- and two-photon interference. This conclusion, in turn, makes it possible to associate the coordinate wave function of a photon (two photons, in the entangled state) measured in some recent experiments with the quasi-classical wave function of a photon (two photons), although it does not take into account its (their) polarization properties. [ABSTRACT FROM AUTHOR]

A formalism for the experimental analysis of mesons produced by a beam of linearly polarized photons is presented. This formalism introduces a more general use of the reflectivity operator. The goal is to recognize resonances in cross-sections, their associated quantum numbers, and production mechanisms by performing partial wave analysis of multiple-meson final states. [ABSTRACT FROM AUTHOR]

We study the inclusive Hb→ Xsγ decay with Hb a beauty baryon, in particular Λb, employing an expansion in the heavy quark mass at O m b − 3 at leading order in αs, keeping the dependence on the hadron spin. For a polarized baryon we compute the distribution d 2 Γ dy d cos θ P , with y = 2Eγ/mb, Eγ the photon energy and θP the angle between the baryon spin vector and the photon momentum in the Hb rest-frame. We discuss the correlation between the baryon and photon polarization, and show that effects of physics beyond the Standard Model can modify the photon polarization asymmetry. We also discuss a method to treat the singular terms in the photon energy spectrum obtained by the OPE. [ABSTRACT FROM AUTHOR]

With the rapid development of high-power petawatt class lasers worldwide, exploring physics in the strong field QED regime will become one of the frontiers for laser–plasma interactions research. Particle-in-cell codes, including quantum emission processes, are powerful tools for predicting and analyzing future experiments where the physics of relativistic plasma is strongly affected by strong field QED processes. The spin/polarization dependence of these quantum processes has been of recent interest. In this article, we perform a parametric study of the interaction of two laser pulses with an ultrarelativistic electron beam. The first pulse is optimized to generate high-energy photons by nonlinear Compton scattering and efficiently decelerate electron beam through the quantum radiation reaction. The second pulse is optimized to generate electron–positron pairs by the nonlinear Breit–Wheeler decay of photons with the maximum polarization dependence. This may be experimentally realized as a verification of the strong field QED framework, including the spin/polarization rates. [ABSTRACT FROM AUTHOR]

We study the semi-metal/insulator quantum phase transition in three-dimensional Dirac semi-metals by solving a set of Schwinger–Dyson equations. We study the effect of an anisotropic fermion velocity on the critical coupling of the transition. We consider the influence of several different approximations that are commonly used in the literature and show that results for the critical coupling change considerably when some of these approximations are relaxed. Most importantly, the nature of the dependence of the critical coupling on the anisotropy depends strongly on the approximations that are used for the photon polarization tensor. On the one hand, this means that calculations that include full photon dynamics are necessary to answer even the basic question of whether the critical coupling increases or decreases with anisotropy. On the other hand, our results mean that it is possible that anisotropy could provide a mechanism to promote dynamical gap generation in realistic three-dimensional Dirac semi-metallic materials. [ABSTRACT FROM AUTHOR]

Chiral plasmonic nanostructures have attracted increasing attention because of their superchiral near‐fields as well as strong far‐field chiral optical response. Recently, the development of chemical synthesis methods enabled the large‐scale manufacturing of three‐dimensional colloidal chiral plasmonic nanocrystals. Further improving the chiral optical response of such nanostructures will greatly facilitate their practical applications. In this work, it is found both in calculations and experiments that chiral cavity plasmon resonances can be excited in film‐coupled chiral Au helicoid nanoparticles, enabling the significant enhancement of the nanostructure chiral optical response. In addition, it is demonstrated from simulation that the chiral cavity mode can modulate the emission polarization of a point electric dipole placed in the nanocavity formed by the nanoparticle and the Au film, allowing the emission of almost circularly polarized photons by the linear dipole with the emission circular polarization anisotropy factor reaching as high as 93%. The film‐coupled chiral plasmonic nanoparticles therefore provide a promising platform for the construction of advanced chiral optical devices such as on‐chip nonreciprocal nanoscale light sources, chiral plasmonic sensors, chiral metamaterials, plasmonically enabled valleytronic devices, and nanophotonic circuits for future on‐chip communication applications. [ABSTRACT FROM AUTHOR]

Many optically active systems possess spatially asymmetric electron orbitals. These generate permanent dipole moments, which can be stronger than the corresponding transition dipole moments, significantly affecting the system dynamics and creating polarized Fock states of light. We derive a master equation for these systems with an externally applied driving field by employing an optical polaron transformation that captures the photon mode polarization induced by the permanent dipoles. This provides an intuitive framework to explore their influence on the system dynamics and emission spectrum. We find that permanent dipoles introduce multiple-photon processes and a photon sideband, which causes substantial modifications to single-photon transition dipole processes. In the presence of an external drive, permanent dipoles lead to an additional process that we show can be exploited to control the decoherence and transition rates. We derive the emission spectrum of the system, highlighting experimentally detectable signatures of optical polarons, and measurements that can identify the parameters in the system Hamiltonian, the magnitude of the differences in the permanent dipoles, and the steady-state populations of the system. [ABSTRACT FROM AUTHOR]

The article focuses on the study of exceptional points (EPs) in non-Hermitian (NH) systems. It is reported that EPs are branch point singularities in the parameter space and are associated with the dispersion of interface states. It is further reported that these EPs has interesting topological properties and find applications in various areas, including sensing, wave propagation, laser emission, and more.

The article presents an innovative approach for on-chip generation of single photons with specific spin and orbital angular momenta (SAM and OAM) states using anisotropic nanodimers. This approach enables the production of circularly polarized single-mode vortex beams with different topological charges, high single-photon purity, and remarkable stability at room temperature, offering promising potential for advanced quantum photonic technologies.

Non-equilibrium spin-polarized transport properties of antiferromagnetic stanene nanoribbons are theoretically studied under the combining effect of a normal electric field and linearly polarized irradiation based on the tight-binding model at room temperature. Due to the existence of spin-orbit coupling in stanene lattice, applying normal electric field leads to splitting of band degeneracy of spin-resolved energy levels in conduction and valence bands. Furthermore, unequivalent absorption of the polarized photons at two valleys which is attributed to an antiferromagnetic exchange field results in unequal spin-polarized photocurrent for spin-up and spin-down components. Interestingly, in the presence of band bending which has been induced by edge potentials, an allowable quantum efficiency occurs over a wider wavelength region of the incident light. It is especially important that the variation of an exchange magnetic field generates spin semi-conducting behavior in the bended band structure. Moreover, it is shown that optical spin-filtering effect is obtained under the simultaneous effect of uniaxial strain and narrow edge potential. [ABSTRACT FROM AUTHOR]

In [1], we performed the first complete computation of the back-to-back inclusive dijet cross-section in Deeply Inelastic Scattering (DIS) at small xBj to next-to-leading order (NLO) in the Color Glass Condensate effective field theory (CGC EFT). We demonstrate here that for dijets with relative transverse momentum P⊥ and transverse momentum imbalance q⊥, to leading power in q⊥/P⊥, the cross-section for longitudinally polarized photons can be fully factorized into the product of a perturbative impact factor and the non-perturbative Weizsäcker-Williams (WW) transverse momentum dependent (TMD) gluon distribution to NLO accuracy. The impact factor can further be expressed as the product of a universal soft factor which resums Sudakov double and single logs in P⊥/q⊥ and a coefficient function given by a remarkably compact analytic expression. We show that in the CGC EFT the WW TMD satisfies a kinematically constrained JIMWLK renormalization group evolution in rapidity. This factorization formula is valid to all orders in Qs/q⊥ for q⊥, Qs ≪ P⊥, where Qs is the semi-hard saturation scale that grows with rapidity. [ABSTRACT FROM AUTHOR]