Thermal Photons Research Articles

Dynamics of Entropy Production Rate in Two Coupled Bosonic Modes Interacting with a Thermal Reservoir.

The Markovian time evolution of the entropy production rate is studied as a measure of irreversibility generated in a bipartite quantum system consisting of two coupled bosonic modes immersed in a common thermal environment. The dynamics of the system is described in the framework of the formalism of the theory of open quantum systems based on completely positive quantum dynamical semigroups, for initial two-mode squeezed thermal states, squeezed vacuum states, thermal states and coherent states. We show that the rate of the entropy production of the initial state and nonequilibrium stationary state, and the time evolution of the rate of entropy production, strongly depend on the parameters of the initial Gaussian state (squeezing parameter and average thermal photon numbers), frequencies of modes, parameters characterising the thermal environment (temperature and dissipation coefficient), and the strength of coupling between the two modes. We also provide a comparison of the behaviour of entropy production rate and Rényi-2 mutual information present in the considered system.

Coherence and Anticoherence Induced by Thermal Fields.

Interesting coherence and correlations appear between superpositions of two bosonic modes when the modes are parametrically coupled to a third intermediate mode and are also coupled to external modes which are in thermal states of unequal mean photon numbers. Under such conditions, it is found that one of linear superpositions of the modes, which is effectively decoupled from the other modes, can be perfectly coherent with the other orthogonal superposition of the modes and can simultaneously exhibit anticoherence with the intermediate mode, which can give rise to entanglement between the modes. It is shown that the coherence effects have a substantial effect on the population distribution between the modes, which may result in lowering the population of the intermediate mode. This shows that the system can be employed to cool modes to lower temperatures. Furthermore, for appropriate thermal photon numbers and coupling strengths between the modes, it is found that entanglement between the directly coupled superposition and the intermediate modes may occur in a less restricted range of the number of the thermal photons such that the modes could be strongly entangled, even at large numbers of the thermal photons.

Probing the properties of dense nuclear matter with photon conversions at NICA

Photons serve as valuable probes of the properties of the hot and dense nuclear matter created in collisions of heavy ions. Thermal photon spectra at RHIC and LHC energies indicate that the temperature of the produced medium far exceeds the temperature of the phase transition to the quark-gluon plasma in lattice QCD calculations. Measurements of thermal photon spectra in heavy ion collisions at lower energies at the future NICA collider may help to trace the transition from partonic to hadronic degrees of freedom. In this contribution, feasibility studies on thermal photon measurements using the photon conversion method in the future MPD experiment at NICA will be reviewed. In this work, a possibility to increase photon reconstruction efficiency with a dedicated conversion layer is presented and feasibility to probe the material budget of the experiment with converted photons is discussed.

Development of the capability for multi-group shielding library generation in the nuclear data processing code NECP-Atlas

The capability to generate multi-group shielding library is developed in the nuclear data processing code NECP-Atlas. To make the code suitable for the applications in different types of reactors, several improvements are made in the code, such as the resonance self-shielding method and energy-group structure optimization. The hyperfine group method is applied to perform resonance self-shielding calculations for different configurations. The energy-group structure optimization method is developed based on the contributon theory to enhance the calculation accuracy of the thermal neutron flux and photon flux. The accuracy of the newly developed capability is verified with the reference results calculated using BUGLE-B7 libraries. Two libraries with optimized neutron energy-group structures of 47 groups and 60 groups are obtained based on the contributon theory. Numerical results show that the thermal neutron flux and photon flux calculated based on the two libraries are greatly improved.

On the Use of Pixelated Plastic Scintillator and Silicon Photomultipliers Array for Coded Aperture Gamma-Neutron Imaging

We report the investigations made on the use of pixelated plastic scintillator (PS) and silicon photomultipliers (SiPMs) array applied to coded aperture gamma-neutron imaging. Specifically, verification of the ability of a multiplexing readout to discriminate and localize neutron interactions was studied. In its intended configuration, the gamma-neutron imager design consists of a coded aperture aligned with a matrix of <inline-formula> <tex-math notation="LaTeX">$12\times12$ </tex-math></inline-formula> PS each coupled to a SiPM. The coded aperture is a rank 7 modified uniformly redundant array (MURA), composed of 1.2 cm of tungsten, with a surface area of 100.4 mm <inline-formula> <tex-math notation="LaTeX">$\times100.4$ </tex-math></inline-formula> mm and placed at 5 cm from the detector. The pixelated PS is composed of polystyrene and standard fluorophores (20 wt&#x0025; PPO, 0.03 wt&#x0025; POPOP) loaded with a lithium carboxylate (Li <inline-formula> <tex-math notation="LaTeX">$\alpha $ </tex-math></inline-formula>-valerate), which allows the triple discrimination between thermal neutrons, fast neutrons, and photons. Each pixel of PS has a dimension of 3.6 mm <inline-formula> <tex-math notation="LaTeX">$\times3.6$ </tex-math></inline-formula> mm <inline-formula> <tex-math notation="LaTeX">$\times3.6$ </tex-math></inline-formula> mm and they are separated from each other by 0.6 mm of polytetrafluoroethylene (PTFE). The photonic and electronic readout consists of the ArrayC-30035-144P SiPM from SensL, Cork, Ireland, connected to the diode coupled charge division readout from AiT. First, this neutron imager design was modeled and simulated using the MCNP6 Monte Carlo code. The encoding capability, field of view, and spatial resolution of the neutron imager were therefore evaluated by simulation. Then, we detailed the experimental setups implemented to demonstrate the feasibility of coupling pixelated PS to SiPM to localize radioactive sources and showed the results obtained. Finally, based on this position-sensitive gamma-neutron detector, a gamma-neutron imager was prototyped and tested.

Feasibility of Measurements of the Properties of Thermal Photons in Heavy-Ion Collisions at the NICA Accelerator

Feasibility of Measurements of the Properties of Thermal Photons in Heavy-Ion Collisions at the NICA Accelerator

Detection of a Prompt Fast-variable Thermal Component in the Multipulse Short Gamma-Ray Burst 170206A

We report the detection of a strong thermal component in the short gamma-ray burst 170206A with three intense pulses in its light curves, throughout which the fluxes of this thermal component exhibit fast temporal variability the same as that of the accompanying nonthermal component. The values of the time-resolved low-energy photon index in the nonthermal component are between about −0.79 and −0.16, most of which are harder than the −2/3 expected in the synchrotron emission process. In addition, we found a common evolution between the thermal component and the nonthermal component, and , where E p,CPL and F CPL are the peak photon energy and corresponding flux of the nonthermal component, and kT BB and F BB are the temperature and corresponding flux of the thermal component, respectively. Finally, we proposed that the photospheric thermal emission and the Comptonization of thermal photons may be responsible for the observational features of GRB 170206A.

Indistinguishability of temporally separated pairwise two-photon state of thermal photons in Franson-type interferometry

The phenomenon of Franson interference with time–energy entangled photon pairs beyond the single-photon coherence length observed upon nonlocal measurement at two space-like separated locations is of particular research interest. Herein, we determine the coherence length of temporally separated pairwise two-photon (TSPT) states of thermal photons emitted from a warm atomic ensemble in Franson-type interferometry, with the setup consisting of two spatially separated unbalanced Michelson interferometers beyond the coherence length of a thermal photon. Using a novel method of square-modulated thermal photons, we show that the sinusoidal Franson-type interference fringe of thermal photons is determined by the presence or absence of TSPT states (corresponding to the time delay between the long and short paths in Franson-type interferometry). We find that the indistinguishability of the TSPT state in the Franson-type interference is independent of the temporal separation of the thermal photons in the TSPT states.

Robustness of quantum correlations in driven cavity optomechanical system interacted with squeezed light

In this paper, we investigate the robustness of quantum correlations in a typical optomechanical quantum source. In particular, we consider two spatially separable optomechanical systems composed of Fabry–Perot cavities. We provide analytic expressions for the covariance matrix of the whole system involving two mechanical modes and two optical modes. We used the logarithmic negativity to quantify the degree of entanglement and the Gaussian quantum discord which is considered to be a witness of the quantumness of correlations in a pairwise system. The behavior of the degrees of the Gaussian quantum discord and entanglement have been analyzed according to the thermal mean photon number, squeezing parameter, and optomechanical cooperativity. With the proper choice of these parameters, it is possible to enhance the quantum correlations in the system. Henceforth, we obtained that the Gaussian quantum discord captured more non-classical properties in comparison with entanglement in various partitions of the optomechanical system under consideration.

Singlet Dioxygen ¹O₂, its Generation, Physico-Chemical Properties and its Possible Hormetic Behavior in Cancer Therapy

Singlet dioxygen 1O2 is one excited state among the three other possible spectroscopic states of molecular oxygen. Here, we first describe the use of published spectroscopic data and thermodynamic modeling based on irreversible entropy production. Such concepts are further applied to the synthesis of singlet dioxygen and its reactions with crucial biological molecules. In a last section, we suggest that singlet dioxygen and ozone may be responsible for the success of radiation therapy, that has been used to treat cancer successfully for over 120 years. Its precise mechanism of action remains controversial. We thus aim to clarify the role of singlet oxygen in radiotherapy and chemotherapy. A partial conversion of ionizing radiation in the body into thermal photons could be assumed. The antitumor effect may involve these thermal photons, such as the one delivered by red/infrared sources. Thermal photons (wavelengths of 635 nm and 1270 nm) convert triplet dioxygen into singlet dioxygen by changing the spin of its outer electrons. Despite its short half-life, Singlet dioxygen is responsible for the activation of multiple free radicals (such as hydrogen peroxide), which may target proteins and DNA, induce either apoptosis or oxidative phosphorylation. At moderate concentrations, thermodynamic data suggests that singlet dioxygen may readily react with water to form a potent pro-apoptotic molecule (ozone), thus decreasing cancer growth. However, at high concentration cytotoxic effects against all kind of cells occurs. This strongly suggests a non-linear hormetic behavior of singlet dioxygen. It is also proposed that cytotoxic chemotherapy induces the same free radicals that singlet dioxygen does. There are also other ways to enhance the production of singlet dioxygen, such as phototherapy using Methylene Blue for instance. As a source of reactive oxygen species (ROS), singlet oxygen could thus be a common agent active both in radiotherapy and chemotherapy. It is probable that the activity of radiation therapy and chemotherapy may be mediated by the conversion of triplet to singlet oxygen. This may explain the oxygen effect such as described in radiotherapy and chemotherapy.

Is the Second Law of Thermodynamics Able to Classify Drugs?

Specialization characterizes pharmacology, with the consequence of classifying the various treatments into unrelated categories. Treating a specific disease usually requires the design of a specific drug. The second law of thermodynamics is the driving force both for chemical reactions and for life. It applies to diseases and treatment. In most common diseases, there is a metabolic shift toward anabolism and anaerobic glycolysis, resulting in the release of entropy in the form of biomass. In accordance with the second principle of thermodynamics, treatment should aim at decreasing the entropy flux, which stays inside the body in the form of biomass. Most treatments aim at increasing the amount of entropy that is released by the cell in the form of thermal photons. As clinically different diseases often requires similar drugs, this calls for reinforcement in a quest for a single unified framework. For example, treatment of aggressive autoimmune diseases requires the same cytotoxic chemotherapy than for cancer. This strongly suggests that despite their apparent disparity, there is an underlying unity in the diseases and the treatments. The shift toward increased entropy release in the form of heat offers sound guidelines for the repurposing of drugs.

Real time thermal photon–photon interactions in the mixed space

Using the effective Lagrangian for the low energy/temperature of photon–photon interaction and the lowest-order photon self-energy is calculated in the Real-Time Formalism (RTF) for an arbitrary path specified by the [Formula: see text]-parameter within the new basis. The causal Green’s functions (without chemical potential) for the scalar field are evaluated to derive the usual thermal propagators in the mixed space. It is shown that the symmetric propagator does not depend on [Formula: see text]-parameter. Furthermore, the photon self-energy is used to calculate some electromagnetic properties, such as dielectric tensor and velocity of light from photon self-energy in the mixed space that greatly simplifies calculations in RTF. Their time dependence is investigated, and a comparison between our results and those obtained by other models is discussed.

Drifting Electrons: Nonreciprocal Plasmonics and Thermal Photonics

Light propagates symmetrically in opposite directions in most materials and structures. This fact -- a consequence of the Lorentz reciprocity principle -- has tremendous implications for science and technology across the electromagnetic spectrum. Here, we investigate an emerging approach to break reciprocity that does not rely on magneto-optical effects or spacetime modulations, but is instead based on biasing a plasmonic material with a direct electric current. Using a 3D Green function formalism and microscopic considerations, we elucidate the propagation properties of surface plasmon-polaritons (SPPs) supported by a generic nonreciprocal platform of this type, revealing some previously overlooked, anomalous, wave-propagation effects. We show that SPPs can propagate in the form of steerable, slow-light, unidirectional beams associated with inflexion points in the modal dispersion. We also clarify the impact of dissipation (due to collisions and Landau damping) on nonreciprocal effects and shed light on the connections between inflexion points, exceptional points at band edges, and modal transitions in leaky-wave structures. We then apply these concepts to the important area of thermal photonics, and provide the first theoretical demonstration of drift-induced nonreciprocal radiative heat transfer between two planar bodies. Our findings may open new opportunities toward the development of nonreciprocal magnet-free devices that combine the benefits of plasmonics and nonreciprocal photonics for wave-guiding and energy applications.

Thermal photonics boosts radiative cooling

Thermal photonics boosts radiative cooling

Observation of Gaussian quantum correlations existence of photons under linear beam splitter

In this paper, we investigate the creation of quantum correlations such as entanglement, the Gaussian quantum discord and quantum steering in a quantum system under consideration via the linear beam splitter with squeezed thermal and a single-mode Gaussian states at the inputs. This quantum system generates bright entangled output two-mode light. Specifically, the quantum entanglement can be enhanced through increasing the purity of the Gaussian state and the squeezing parameter at the input states. The quantum correlations reveal similar characteristics for each case. That means when we increase the non-classicality, purity and squeezing parameter, the quantum correlations show enhanced profile. On the other hand, upon increasing the mean thermal photon number at the input, the quantum correlations indicate inverse relation.

Tunable Near-Field Radiative Effect in a Td – WTe2 Single Layer

In contrast to artificial metamaterials, natural two-dimensional (2D) hyperbolic materials are able to support higher electromagnetic confinement and stronger photonic density of states. This means natural 2D hyperbolic materials have fascinating potential for applications in thermal photonics. In this work, we investigate mechanisms of near-field thermal radiation (NFTR) in a ${\mathrm{T}}_{d}$--${\mathrm{WTe}}_{2}$ single layer at the nanoscale using the fluctuation-dissipation theorem and density-functional theory. The results show that NFTR of ${\mathrm{T}}_{d}$--${\mathrm{WTe}}_{2}$ can be 3 orders of magnitude larger than the blackbody limit. By using the photonic tunneling coefficient and the plasmon dispersion, we present a comprehensive study of plasmonic properties of ${\mathrm{T}}_{d}$--${\mathrm{WTe}}_{2}$. Moreover, our first-principles calculations predict that application of a certain amount of mechanical stress can trigger topological transition between the elliptic and the hyperbolic surface states by regulating the Fermi surface and interband excitation threshold. Lastly, we systematically exhibit the evolution of surface plasmon polaritons in ${\mathrm{T}}_{d}$--${\mathrm{WTe}}_{2}$ under mechanical stress and analyze the performance of using mechanical stress to modulate the corresponding NFTR. Our work explores the great potential of tunable radiative heat flux in ${\mathrm{T}}_{d}$--${\mathrm{WTe}}_{2}$, which is explained here through the peculiar nature of hyperbolic surface plasmons.

Molecular Dynamics Investigation on Thermal Conductivity and Photon Behaviors of Graphene With Sierpinski Carpet Fractal Defects

The thermal conductivity (TC) of graphene with Sierpinski carpet fractal (SCF) and regular carpet (RC) defects is numerically studied by the non-equilibrium molecular dynamics (NEMD) method. The influences of porosity, fractal levels, and types of defects on the TC of graphene are clarified, and the underlying mechanisms of phonon behaviors are uncovered. The numerical results indicate that the defects in graphene induce the atoms that have the heat transfer blockage effect, and thus, the TC of defective graphene decreases with increasing porosity. With the increase in fractal levels, more atoms have the heat transfer blockage effect, which induces the TC of graphene with SCF defects to sharply decrease. Moreover, compared with the graphene with RC defects, more atoms participate in the heat transfer blockage under the graphene with SCF defects, which leads to the lower TC of graphene with SCF defects.

Shedding light on thermal photon and dilepton production

Electromagnetic radiation from the quark-gluon plasma (QGP) is an important observable to be considered in heavy ion collision experiments. I will provide an update on recent advancements from perturbation theory and quenched lattice simulations. The resummed next-to-leading order (NLO) emission rate has recently been decomposed into transverse and longitudinal components, and extended to non-zero baryon chemical potential. The associated spectral function has also been tested against the Euclidean correlator, for continuum-extrapolated lattice data (at μB = 0).

High-fidelity storage and on-demand retrieval of quantum states via a microwave waveguide

On-demand quantum memory is an important step towards practical applications in various quantum information tasks such as long-distance entanglement distribution, quantum computation, and quantum networks. In this work, based on stimulated Raman adiabatic passage (STIRAP) protocol, we introduce a controllable delay between the reading pulse and writing pulse so that the quantum state can be stored in the superconducting waveguide and finally retrieved on demand with high fidelity. Through systematic numerical simulations, we find that if the duration of the writing pulse is set to be in a certain range, the readout unit is capable of retrieving the quantum state stored in the waveguide with high fidelity at any moment after a critical time. Moreover, we also investigate the robustness of our protocol, and find that the fidelity is robust against both the average number of thermal photons in the waveguide and the duration of the reading pulse. The numerical results also show that the pulse area in our protocol is only about one third of that in the original STIRAP protocol. Our protocol provides a practical way to combine the advantages of both on-demand quantum memory and the STIRAP protocol.

High-Fidelity Qubit Readout Using Interferometric Directional Josephson Devices

Nonreciprocal microwave devices, such as circulators and isolators, are needed in high-fidelity qubit readout schemes to unidirectionally route the readout signals and protect the qubits against noise coming from the output chain. However, cryogenic circulators and isolators are prohibitive in scalable superconducting architectures because they rely on magnetic materials. Here, we perform a fast (750 ns) high-fidelity (95%) quantum nondemolition readout of a coherent superconducting qubit ($T_{1}=52$ $\mu s$, $T_{\rm{2E}}=35$ $\mu s$) without any nonreciprocal magnetic devices. We employ in our readout chain a microwave-controlled qubit-Readout Multi-Chip Module (qRMCM) that integrates interferometric directional Josephson devices consisting of an isolator and a reconfigurable isolator/amplifier device and an off-chip low-pass filter. Using the qRMCM, we demonstrate isolation up to 45 dB within 13 MHz, when both directional devices are operated as isolators, and low-noise amplification in excess of 10 dB within a dynamical bandwidth of $10$ MHz, when the reconfigurable device is operated as an amplifier. We also demonstrate using the variable isolation of the qRMCM an in-situ enhancement of the qubit coherence times $T_{\rm{\varphi}}$ and $T_{\rm{2E}}$ by two orders of magnitude (i.e., from $T_{\rm{\varphi}}=T_{\rm{2E}}=0.5$ $\mu s$ to $T_{\rm{\varphi}}=90$ $\mu s$ and $T_{\rm{2E}}=50$ $\mu s$). Furthermore, by directly comparing the qRMCM performance to a state-of-art configuration (with $T_{\rm{2E}}\approx 2T_{1}$) that employs a pair of wideband magnetic isolators, we find that the excess pure dephasing measured with the qRMCM (for which $T_{\rm{2E}}\approx T_{1}$) is likely limited by residual thermal photon population in the readout resonator. Improved versions of the qRMCM could replace magnetic circulators and isolators in large superconducting quantum processors.