Photon Wave Research Articles

Momentum spectrum of nonlinear Breit-Wheeler pair production in spacetime fields

We show how to use a worldline-instanton formalism to calculate, to leading order in the weak-field expansion, the momentum spectrum of nonlinear Breit-Wheeler pair production in fields that depend on time and one spatial coordinate. We find a nontrivial dependence on the width, λ, of the photon wave packet, and the existence of a critical point λc. For λ<λc and a field with one peak, the spectrum has one peak where the electron and positron have the same energy. For λ>λc this splits into two peaks. We calculate a high-energy (Ω≫1) expansion, which to leading order agrees with the results obtained by replacing the spacetime field with a plane wave and using the well-known Volkov solutions. We also calculate an expansion for Ω∼a0≫1, where the field is strong enough to significantly bend the trajectories of the fermions despite Ω≫1. Published by the American Physical Society 2024

Efficient, high-fidelity single-photon switch based on waveguide-coupled cavities

We demonstrate theoretically that waveguide-coupled cavities with embedded two-level emitters can act as a highly efficient, high-fidelity single-photon switch. The photon switch is an optical router triggered by a classical signal—the propagation direction of single input photons in the waveguide is controlled by changing the emitter-cavity coupling parameters , for example, using applied fields. The switch reflects photons in the weak emitter-cavity coupling regime and transmits photons in the strong coupling regime. By calculating transmission and reflection spectra using the input-output formalism of quantum optics and the transfer matrix approach, we obtain the fidelity and efficiency of the switch with a single-photon input in both regimes. We find that a single waveguide-coupled cavity can route input photon wave packets with near-unity efficiency and fidelity if the wave packet width is smaller than the cavity mode linewidth. We also find that using multiple waveguide-coupled cavities increases the switching bandwidth, allowing wider wave packets to be routed with high efficiency and fidelity. For example, an array of three waveguide-coupled cavities can reflect an input Gaussian wave packet with a full width at half-maximum of 1 nm (corresponding to a few-picosecond pulse) with an efficiency Er=96.4% and a fidelity Fr=97.7%, or transmit the wave packet with an efficiency Et=99.7% and a fidelity Ft=99.8%. Such efficient, high-fidelity single-photon routing is essential for scalable photonic quantum technologies. Published by the American Physical Society 2024

Three decades riding the photonic crystal fiber wave: an interview with Prof. Philip Russell

Three decades riding the photonic crystal fiber wave: an interview with Prof. Philip Russell

A Rydberg-Bohr-de Broglie Algebraic Model of Hydrogen Atoms

Bohr ignored the electromagnetic interaction of moving charges in atoms and only considered Coulomb forces, thus encountering half frequency difficulties. This article considers the Lorentz force to make the classical Bohr model consistent with modern quantum theory, uses de Broglie's standing wave principle instead of Bohr's quantization assumption, derives the energy level formula for hydrogen atoms, and explains the radiation mechanism of hydrogen atomic spectra. The hydrogen atom in a spectral tube emits a photon wave train during one free path, and the wavelength of the photon is the eigen wavelength of its wave train. The head wavelength of the wave train is four thirds of its eigen wavelength, and the tail wavelength of the wave train is two-thirds of its eigen wavelength.

Rydberg-atom-based system for benchmarking millimeter-wave automotive radar chips

Rydberg atomic sensors and receivers have enabled sensitive and traceable measurements of rf fields at a wide range of frequencies. Here, we demonstrate the detection of electric field amplitude in the extremely-high-frequency (EHF) band, at 131GHz. In our approach, we propagate the EHF field in a beam, with control over its direction and polarization at the detector using photonic wave plates. This way, we take advantage of the highest detection sensitivity, registered for collinear propagation and circular polarization. To exhibit the potential for applications in this kind of Rydberg-atom-based detection, we perform test measurements on the EHF field emitted from an on-chip radar, which is designed to be used in the automotive industry as a vital sign detector. Our work elucidates practical applications of Rydberg-atom media and photonic metamaterial elements. Published by the American Physical Society 2024

Probing gluon GTMDs of the proton in deep inelastic diffractive dijet production at HERA

We calculate several differential distributions for diffractive dijets production in ep→e′jet jetp in the perturbative QCD dipole approach using off diagonal unintegrated gluon distributions (generalized transverse momentum dependent distributions, GTMDs). Different models from the literature are used. We concentrate on the contribution from exclusive qq¯ dijets. Results of our calculations are compared to H1 and ZEUS data, including specific experimental cuts in our calculations. In general, except for one GTMD, our results are below the HERA data. The considered mechanism is expected to gives a sizeable contribution to the ZEUS data, while it is negligible in the kinematics of the H1 measurement. This is in contrast to recent results from the literature where the normalization was adjusted to some selected distributions of the H1 collaboration and no agreement with other observables was checked. The ZEUS data provide stricter limitations on the GTMDs than the H1 data. We conclude, based on comparison to different observables, that the calculated cross sections are only a small fraction of the measured ones which contain probably also processes with pomeron remnant. Alternatively one could try to explain the experimental data by inclusion of qq¯g component of the photon wave function. We present also azimuthal correlations between the sum and the difference of dijet transverse momenta. The cuts on transverse momenta of jets generate corresponding azimuthal correlations that can be misidentified as due to elliptic gluon distributions. Published by the American Physical Society 2024

Consciousness: a quantum optical effect in fluorescent protein pathways

This paper presents a physical mechanism of embodied consciousness based on the dynamic organicity theory. We use the entropic pilot wave theory to describe the quantum dipole oscillations from dipole-bound delocalized (quasi-free) electrons in nonpolar nanocavities of aromatic amino acid residues (benzene moiety /cyclic hydrocarbons that contain resonance structures) and their fluorescent pathways. These pathways contain cavity quasipolariton condensates composed of quantized polarization waves of entangled photons. The behavior of oscillating molecular dipoles is influenced by the quantum nature of dynamic organicity, which causes energy fluctuations necessary to move delocalized electrons and create bare polaritons (quantized polarization waves). These waves correspond to photon quasiparticles interacting with water molecules to form quasipolaritons, softened by interacting with hydroxide ions (OH-) within crystal lattices of interfacial water H30. When [H3O+]=[OH−], the solution is neutral in hydrophobic nanocavities. In such nonpolar cavities, evanescent photons (non-radiative transitions in the absence of any source) are emitted while protons (H+) diffuse due to recombination with hydroxide (OH-) ions, acting as protonic analogs of ‘holes’ or excitons. In protein pores, proton motion strongly coupled with π-electron delocalization is a conduit for exciton-photon (polariton) and its polarization wave component. Internal energy fluctuations comprise both quantum potential energy and negative quantum kinetic energy. We explore how quantum potential energy influences the negentropic effect of a 'repulsive force' guided by entropic pilot waves through pilot wave force (negentropic force), functioning as an information-based action of the polarization wave as a conduit of the cavity quasipolariton. When the rate of change of quantum entropy is zero, and momentum of the polarization wave is zero the internal energy transduction between quantum potential energy to quantum kinetic energy manifests as the negentropic force and facilitates the movement of information-based action for information encoding when negative quantum kinetic energy happens at certain times. Experiments have shown that biphoton entanglement interferes with anaesthetics. We postulate that the disruption of cavity polaritonic condensate through its polarization wave component disrupts the decoding of information, suggesting consciousness is attributed to a quantum optical effect. Therefore, we further theorize that consciousness is attributed to the negative quantum kinetic energy of the polarization wave, which provides an informational structure of multiscale redundancy when negentropic action reduces information redundancy. This has profound implications for understanding consciousness as nonmechanical action channeled through negentropic force when the rate of change of quantum entropy is zero.

Clarification of the transverse orbital angular momentum of spatiotemporal optical vortices

Advances in the generation and the application of spatiotemporal optical vortices (STOV) are proceeding fast, but fundamental aspects of their nature remain obscure. Bliokh (2023 Phys. Rev. A 107 L031501) (PRA) and Porras (2023 Prog. Electromagn. Res. 177 95) (PIER) provide contradictory results on the transverse orbital angular momentum (OAM) carried by STOVs. We show that the results by Porras in PIER and by Bliokh in PRA refer to different STOVs and are all correct. In PIER, STOVs are elliptical at given cross section and time, or in space-time, but not in three-dimensional space. In PRA, STOVs are elliptical in space but not in space-time. This is evidenced from two dual, equivalent theories on the transverse OAM where a wave packet is seen in space-time evolving with propagation distance or in space evolving in time, that account for all values of the total, intrinsic and extrinsic OAM in PIERS and PRA. However, the intrinsic OAM with respect to the photon wave function center in PRA is not generally conserved, which advocates for the energy center in PIER as the STOV center. We argue that STOVs are generated in experiments to purportedly have elliptical symmetry in space-time. The values provided in PIER should then be taken as the reference for elliptical STOVs, and the theory therein to evaluate the transverse OAM of other wave packets. Hancock et al (2021 Phys. Rev. Lett. 127 193901; 2024 Phys. Rev. X 14 011031) erroneously attribute the transverse OAM of elliptical STOVs in space to the elliptical STOVs in space-time that they consider theoretically and can generate in their experiments.

Quantum-dot spin-VCSELs subject to optical injection and feedback for flexible photonic millimeter wave generation

A novel microwave and millimeter wave signal generation system is proposed and numerically demonstrated using an optically pumped quantum dot (QD) spin-polarized vertical-cavity surface-emitting laser (spin-VCSEL) with optical injection. Different from previous optical injection systems, the signal frequency in our proposed system is dominated by both the birefringence-splitting and injection detuning frequencies. By flexibly tailoring the frequency detuning and birefringence rate, the frequency ranges from a few gigahertz to nearly 150 GHz can be obtained. To evaluate the signal quality, the dynamical behaviors of the proposed system and the characteristics of the generated millimeter wave signal are evaluated including the center frequency, power, linewidth, and phase variance. We further adopt the optical feedback structure to improve the microwave and millimeter wave signal performance. Results show that the signal linewidth and phase variance can be optimized by three to four orders of magnitude. Compared to the case of a solitary QD spin-VCSEL, this work shows more stable performance, particularly in the frequency range above 90 GHz. This scheme offers an approach for high-purity microwave and millimeter sources in wireless communication and radar systems.

Nuclear quantum memory for hard x-ray photon wave packets.

Optical quantum memories are key elements in modern quantum technologies to reliably store and retrieve quantum information. At present, they are conceptually limited to the optical wavelength regime. Recent advancements in x-ray quantum optics render an extension of optical quantum memory protocols to ultrashort wavelengths possible, thereby establishing quantum photonics at x-ray energies. Here, we introduce an x-ray quantum memory protocol that utilizes mechanically driven nuclear resonant 57Fe absorbers to form a comb structure in the nuclear absorption spectrum by using the Doppler effect. This room-temperature nuclear frequency comb enables us to control the waveform of x-ray photon wave packets to a high level of accuracy and fidelity using solely mechanical motions. This tunable, robust, and highly flexible system offers a versatile platform for a compact solid-state quantum memory at room temperature for hard x-rays.

Inverse design of ultrawideband one-dimensional metamaterial photonic filters using Riccati equation constrained gradient descent.

One-dimensional photonic wave devices exhibit a pivotal role in wave engineering. Despite their relative simplicity, designing 1D wave devices that implement complex functionalities over a broad frequency range is challenging and requires careful sculpting and multiple optimizations. This paper theoretically and experimentally demonstrates a new inverse design paradigm to achieve a desired broadband frequency response efficiently. Specifically, we calculate the required dielectric profile along the device using constrained gradient descent optimization to minimize the L 2 norm between the desired and actual responses. In each optimization step, we avoid the need to solve the complete set of Maxwell equations by using Riccati's equation or its discrete ancestor as the optimization constraint for calculating the local reflection coefficient. Using this approach, we design several unorthodox filters, such as dual-band narrowband bandpass filters located within a wideband bandstop and ultrawideband first and second-order differentiators. The technique produces excellent results for ultrawideband frequency ranges, with very low computational complexity and, remarkably, with a single trivial guess for the optimization starting point. We experimentally implemented the two differentiator designs in radio frequencies using electronic circuit elements that comprise a metamaterial transmission line structure.

Centralized full-duplex seamless photonic mmW fronthaul link based on phase modulation

We experimentally demonstrate a photonic full-duplex seamless millimeter wave fronthaul link, based on phase modulation, to address the challenges arising from the increased demands on the mobile fronthaul capacity and network densification toward 5G and beyond. The proposed system relies on phase modulation techniques, implemented at both the central office (CO) and remote radio head (RRH), to achieve optical frequency up-conversion of the downlink (DL) signal and optical modulation of the down-converted uplink (UL) signal. Furthermore, our approach includes the frequency down-conversion of the 40 GHz UL signal through an optically generated local oscillator (LO) signal in the RRH, while the laser employed for UL data transmission is situated at the CO, simplifying the remote site’s equipment. An optical waveshaper serves here as a programmable optical filter to provide signals for DL frequency up-conversion, LO generation, and also the optical carrier for UL transmission. In our experimental validation, we have tested our proposed system using 64-quadrature amplitude modulation (64-QAM) for the DL at a frequency of 41 GHz and quadrature phase shift keying (QPSK) for the UL at a frequency of 40 GHz. Notably, our results demonstrate the successful transmission of up to 200 MHz bandwidth for both digital modulation schemes, all while maintaining the error vector magnitude (EVM) well below the specified threshold. Additionally, when employing 5G new radio (NR) orthogonal frequency-division multiplexing (OFDM) signals with the same modulation formats for both links in full-duplex communication, we achieved EVM values as low as 5.2% for the DL and 6.9% for the UL, further highlighting the efficacy and robustness of our proposed solution.

Estimation with Ultimate Quantum Precision of the Transverse Displacement between Two Photons via Two-Photon Interference Sampling Measurements.

We present a quantum sensing scheme achieving the ultimate quantum sensitivity in the estimation of the transverse displacement between two photons interfering at a balanced beam splitter, based on transverse-momentum sampling measurements at the output. This scheme can possibly lead to enhanced high-precision nanoscopic techniques, such as superresolved single-molecule localization microscopy with quantum dots, by circumventing the requirements in standard direct imaging of camera resolution at the diffraction limit, and of highly magnifying objectives. Interestingly, we show that our interferometric technique achieves the ultimate spatial precision in nature irrespectively of the overlap of the two displaced photonic wave packets, while its precision is only reduced of a constant factor for photons differing in any nonspatial degrees of freedom. This opens a new research paradigm based on the interface between spatially resolved quantum interference and quantum-enhanced spatial sensitivity.

Sensing of volatile organic compounds using one-dimensional photonic crystal Bloch surface waves and internal optical modes

Bloch surface wave (BSW) and internal optical modes (IOMs) of one-dimensional photonic crystals (1DPhCs) have been explored for sensing purposes in the photonic crystal coupled reflectance (PCCR) geometry using the Kretschmann-Raether (KR) prism-coupling configuration. 1DPhCs coated with polyvinyl alcohol (PVA) thin films of two distinct thicknesses: 18 nm (referred to as PhC18) and 24 nm (referred to as PhC24) were fabricated. The response of the PCCR to the changes occurring in the PVA coated 1DPhC structures were studied by spraying volatile organic compounds, 1-propanol and 2-propanol onto the surface of the 1DPhCs. The BSWs excited under TE polarization are found to be very sensitive to perturbations at the 1DPhC interface. 1-propanol displays larger wavelength shifts and longer recovery times of the 1DPhC modes than 2-propanol because of its lower vapor pressure and higher reactivity to PVA.

On-Demand Generation of Indistinguishable Photons in the Telecom C-Band Using Quantum Dot Devices.

Semiconductor quantum dots (QDs) enable the generation of single and entangled photons, which are useful for various applications in photonic quantum technologies. Specifically for quantum communication via fiber-optical networks, operation in the telecom C-band centered around 1550 nm is ideal. The direct generation of QD-photons in this spectral range with high quantum-optical quality, however, remained challenging. Here, we demonstrate the coherent on-demand generation of indistinguishable photons in the telecom C-band from single QD devices consisting of InAs/InP QD-mesa structures heterogeneously integrated with a metallic reflector on a silicon wafer. Using pulsed two-photon resonant excitation of the biexciton-exciton radiative cascade, we observe Rabi rotations up to pulse areas of 4π and a high single-photon purity in terms of g(2)(0) = 0.005(1) and 0.015(1) for exciton and biexciton photons, respectively. Applying two independent experimental methods, based on fitting Rabi rotations in the emission intensity and performing photon cross-correlation measurements, we consistently obtain preparation fidelities at the π-pulse exceeding 80%. Finally, performing Hong-Ou-Mandel-type two-photon interference experiments, we obtain a photon-indistinguishability of the full photon wave packet of up to 35(3)%, representing a significant advancement in the photon-indistinguishability of single photons emitted directly in the telecom C-band.

Quantum analysis of a Mach–Zehnder interferometer with propagating a single photon Gaussian wave packet

In this paper, a Mach–Zehnder interferometer is analyzed with a single photon Gaussian wave packet at one of its input ports and vacuum state at the other input port. Various noises arising in the Mach–Zehnder interferometer such as photon flux noise and quadrature noise are mathematically analyzed. The effect of variation in device parameters on the power spectral density at the output ports of the Mach–Zehnder interferometer is studied. It is observed that the power spectral density of photon flux noise autocorrelation at the output ports of a Mach–Zehnder interferometer is a function of phase shift, whereas the power spectral density of quadrature noise autocorrelation at the output ports of a Mach–Zehnder interferometer is a function of frequency of a single photon wave packet and the phase shift. The analysis carried out in this paper will be helpful in understanding the quantum fluctuations in the design of quantum logic devices and circuits where the Mach–Zehnder interferometer is a core building block.

Topological elastic interface states in hyperuniform pillared metabeams

Topological states have been receiving a great deal of interest in various wave problems, such as photonic, acoustic, and elastic waves. However, few studies of topological elastic waves in non-periodic systems have been reported. Recently, hyperuniform systems suppressing long-range order while partly maintaining short-range order have provided new opportunities to control waves. In this work, we study the elastic topological interface states appearing between two Su–Schrieffer–Heeger (SSH)-like pillared metabeams where each metabeam, is constituted by a mirror symmetric hyperuniform structure. The SSH-like model is constructed by combining two hyperuniform metabeams with inverted configurations. We demonstrate that this structure could open new bandgaps at low frequencies, of which some are nontrivial and can support topological interface modes. We further show that the number of low-frequency bandgaps supporting the topological modes increases with the level of randomness, hence providing a high number of interface modes in the same structure. The robustness of the topological interface states against random perturbations in the pillars’ positions is further verified. Our work offers a reliable platform for studying topological properties and hyperuniform metamaterials and designing wave control devices for low-frequency wave attenuation and robust energy localization.

Electromagnetic Waves, Light and Information

In this paper electromagnetic waves and visible light were examined. Information and communication technology were studied. Electromagnetic radiation, quantum energy, photon and electromagnetic waves were considered. The methodology of macroscopic and microscopic approach were used. Discrete energy quantity, photon, and information were employed. In this paper the light spread law was derived, first time in literature. The sun light changeable velocity was defined. Also, equation for information transfer functionalities were developed. These results can be applied in communication.

On numerical and approximate analytical modeling of single- and two-photon Young's experiment using the photon coordinate wave function

In modern areas of photonics, the physical description of the interaction of photons with matter in the control, transmission and registration of single-photon and two-photon states implemented in practice is of great importance. An appropriate acceptable description may be faced with the need to take into account various kinds of interference effects associated with these states. Meanwhile, even the most “simple” case of single-photon interference in Young's experiment requires the use of a rather complex apparatus of quantum electrodynamics. This article explains one- and two-photon interference in Young's thought experiment based on the photon wave function (PWF) in coordinate representation. This explanation is illustrated by two examples of wavelengths: 10.6 μm and 1.5 cm. For both examples, two approaches to PWF modeling are used: “purely quantum-mechanical” and “quasi-classical”. In the first approach, a 6-component coordinate PWF is constructed using a spherically symmetric momentum distribution in a wave packet, followed by numerical and approximate analytical calculations. In the second approach, a one-component “quasi-classical” PWF is constructed, which corresponds to either electric dipole radiation or simulated spherically symmetric radiation. In all cases, the same pronounced interference pattern was obtained, which allows us to conclude that not only the quantum-mechanical coordinate PWF is able to explain the phenomena of one- and two-photon interference, but also a much simpler “quasi-classical” PWF. This conclusion sheds light on the theoretical interpretation of the measurement of the coordinate PWF in some recent experiments.

The refractive index of a single atom experienced by a single photon

The refractive index of a system is often viewed as the collective response of a medium to an electromagnetic field. Nevertheless, even if targeted at a single atom, the incoming light undergoes the dispersion. By studying the propagation of a single photon interacting with a two-level atom, we examine the dispersion behavior, calculate the phase and group velocity of the photon wave packet, and further analyze the dispersion experienced by the photon. These findings are critical for advancing long-distance quantum communications.