Radiative Properties of Rydberg States in Resonant Cavities

Microwave Emissions and the Problem of Modern Viral Diseases

The results of a study on the mechanisms of the influence of an increased level of microwave radiation on the growth of infectious, primarily viral, diseases in the environment are presented. This is the radiation of the earth's ionosphere, which reached its maximum in the late 1980s-early 2000s, following an increase in the level of solar activity since the 17th century. Over the past 30 years, the anthropogenic electromagnetic background has increased 100 times due to the development of cellular mobile communications and computerization. The predicted interaction of natural and anthropogenic sources of microwaves sharply increases their negative impact on the ecological situation. Of particular concern is the active spread in recent years of the new 5G communication standard; in the future, it is the development of the most dangerous millimeter range in our country. Energy from the environment in the microwave range can cause "unexpected behavior" in the DNA of viruses. Clarifications to the recommendations of experts on the protection of the population with the help of electromagnetic shielding, obtained in the framework of supramolecular physics of the environment, are proposed.

Underlying SUSY in a generalized Jaynes-Cummings model

We present a general qubit-boson interaction Hamiltonian that describes the Jaynes–Cummings model and its extensions as a single Hamiltonian class. Our model includes non-linear processes for both the free qubit and boson field as well as non-linear, multi-boson excitation exchange between them. It shows an underlying algebra with supersymmetric quantum mechanics features allowing an operator based diagonalization that simplifies the calculations of observables. As a practical example, we show the evolution of the population inversion and the boson quadratures for an initial state consisting of the qubit in the ground state interacting with a coherent field for a selection of cases covering the standard Jaynes–Cummings model and some of its extensions including Stark shift, Kerr-like, intensity dependent coupling, multi-boson exchange and algebraic deformations.

Bench-Top Cooling of a Microwave Mode Using an Optically Pumped Spin Refrigerator

We experimentally demonstrate the temporary removal of thermal photons from a microwave mode at 1.45 GHz through its interaction with the spin-polarized triplet states of photo-excited pentacene molecules doped within a p-terphenyl crystal at room temperature. The crystal functions electromagnetically as a narrowband cryogenic load, removing photons from the otherwise room-temperature mode via stimulated absorption. The noise temperature of the microwave mode dropped to 50_{-32}^{+18}  K (as directly inferred by noise-power measurements), while the metal walls of the cavity enclosing the mode remained at room temperature. Simulations based on the same system's behavior as a maser (which could be characterized more accurately) indicate the possibility of the mode's temperature sinking to ∼10  K (corresponding to ∼140 microwave photons). These observations, when combined with engineering improvements to deepen the cooling, identify the system as a narrowband yet extremely convenient platform-free of cryogenics, vacuum chambers, and strong magnets-for realizing low-noise detectors, quantum memory, and quantum-enhanced machines (such as heat engines) based on strong spin-photon coupling and entanglement at microwave frequencies.

Tavis-Cummings Model with Moving Atoms

In this work, we examine a nonlinear version of the Tavis–Cummings model for two two-level atoms interacting with a single-mode field within a cavity in the context of power-law potentials. We consider the effect of the particle position that depends on the velocity and acceleration, and the coupling parameter is supposed to be time-dependent. We examine the effect of velocity and acceleration on the dynamical behavior of some quantumness measures, namely as von Neumann entropy, concurrence and Mandel parameter. We have found that the entanglement of subsystem states and the photon statistics are largely dependent on the choice of the qubit motion and power-law exponent. The obtained results present potential applications for quantum information and optics with optimal conditions.

Entropy production and thermalization in the one-atom maser

In the configuration in which two-level atoms with an initial thermal distribution of their states are sent in succession to a cavity sustaining a single mode of electromagnetic radiation, one atom leaving the cavity as the next one enters it (as in the one-atom maser), Jaynes and Cummings showed that the steady state of the field, when many atoms have traversed the cavity, is thermal with a temperature different than that of the atoms in the off-resonant situation. Having an interaction between two subsystems which maintains them at different temperatures was then understood as leading to an apparent violation of energy conservation. Here we show, by calculating the quantum entropy production in the system, that this difference of temperatures is consistent with having the subsystems adiabatically insulated from each other as the steady state is approached. At resonance the insulation is removed and equilibration of the temperatures is achieved.

Nonclassical effects of a two-level spin system interacting with a two-mode cavity field via two-photon transition

The interaction of a two-level cyclic XY n-spin model with a two-mode cavity field involving two-photon transitions is investigated through a generalized Jaynes-Cummings model in the rotating-wave approximation. The two-photon interacting Hamiltonian becomes from the replacement of each single-mode field in the one-photon interacting Hamiltonian with the second-harmonic generation. It was assumed that initially the correlated field modes are in disentangled coherent states having the same photon distribution and that the spin system is in an excited state. At any time t > 0, the spin system and the field are in an entangled state, in this case, via a unitary time evolution operator. Thus, the spontaneous decay of a spin level was treated by considering the interaction of the two-level spin system with the modes of the universe in the vacuum state. The different cases of interest, characterized in terms of a detuning parameter for each mode, which emerge from nonvanishing commutation relations, were analytically implemented and numerically discussed for various values of the initial mean photon number and spin-photon coupling constants. Photon distribution, time evolution of the spin population inversion, as well as the statistical properties of the field leading to the possible production of nonclassical states, such as antibunched light, violations of the Cauchy-Schwartz inequality, and second- and fourth-order squeezing, are examined. The case of zero detuning of both modes was treated in terms of a linearization of the expansion of the time evolution operator, while in other three cases, the computations were conducted via second- and third-order Dyson perturbation expansion of the time evolution operator matrix elements for the excited and ground states of the spin system, respectively.

Laser control of collective spontaneous emission

The collective spontaneous emission of a pair of two coupled three-level radiators in vacuum is investigated in the presence of a possibly intense laser field. The parameters describing the collective interaction along with the population and decay rates of all involved dressed states are shown to be controllable by the applied laser field. In particular, all populations of the collective system may be transferred at will in a reversible way into a subradiant state, allowing effective storage and manipulation of the quantum system.

Robust long-distance entanglement and a loophole-free bell test with ions and photons

Two trapped ions that are kilometers apart can be entangled by the joint detection of two photons, each coming from one of the ions, in a basis of entangled states. Such a detection is possible with linear optical elements. The use of two-photon interference allows entanglement distribution free of interferometric sensitivity to the path length of the photons. The present method of creating entangled ions also opens up the possibility of a loophole-free test of Bell's inequalities.

Subsystem purity as an enforcer of entanglement

We show that entanglement can always arise in the interaction of an arbitrarily large system in any mixed state with a single qubit in a pure state. This small initial purity is enough to enforce entanglement even when the total entropy is close to maximum. We demonstrate this feature using the Jaynes-Cummings interaction of a two-level atom in a pure state with a field in a thermal state at an arbitrarily high temperature. We find the time and temperature variation of a lower bound on the amount of entanglement produced and study the classical correlations quantified by the mutual information.