Nonresonant Photon Research Articles

Study of the Method of Photon Neutralization of Powerful Beams of Negative Ions at the Budker Institute of Nuclear Physics

A short review of the studies carried out at the Budker Institute of Nuclear Physics, Siberian Branch, Russian Academy of Sciences (BINP SB RAS) on the photon neutralization of the beams of negative ions is presented. The principal distinctive feature of the presented approach consists in the nonresonant accumulation of photons in a limited space. Their confinement is based on the adiabatic motion of photons in a system of concave mirrors, which is insensitive to the quality of the injected radiation. An analysis is carried out of the possibility of using the neutralizer based on such a nonresonant photon trap in large-scale installations such as ITER and TRT, and a future experiment is described on the photon neutralization using a beam of negative hydrogen ions with energy up to 130 keV and a current of about 10 mA.

Frequency tunable single photon diode based on giant atom coupling to a waveguide.

The single photon scattering properties in a waveguide coupling to a giant atom with a three-level system are investigated theoretically. One of the transitions of the giant atom couples to the waveguide at two points while the other one is driven by a classical field. Using the analytical expressions of the single photon scattering amplitudes, the conditions for realizing perfect single photon nonreciprocal scattering are discussed in both Markovian regime and non-Markovian regime. In the Markovian regime, the perfect non-reciprocity can be realized by adjusting the external classical field, the energy dissipation of the giant atom, the phase difference between the two coupling strengths and the accumulated phase resulting from the photon propagating between the two coupling points. In the non-Markovian regime, the non-reciprocal scattering phenomenon becomes more abundant due to the time delay. However, the analytical results show that the perfect non-reciprocity can still be achieved. When the incident photon is resonant with the giant atom, the nonreciprocity can be switched by controlling the classical field. For the non-resonant single photon, one can adjust the Rabi frequency of the classical field to obtain the perfect non-reciprocal single photon transmission. Our work provides a manner to realize a frequency tunable single photon diode.

Distant Magnon-Magnon Coupling Mediated by Nonresonant Photon

In this paper, we theoretically and experimentally study the distant magnon-magnon coupling mediated by nonresonant photons. We establish a magnon-photon-magnon coupling model for two CrCl3 crystals spacial separated on a microstrip line. By changing the phase difference of the samples from 0 to π in order to manipulate the distant magnons from coherent coupling to dissipative coupling, our coupling model predicts that the dispersion is tunable from a level repulsion to a level attraction. In addition, we experimentally demonstrate that two spacial separated CrCl3 crystals over a distance of 1.2 cm couple each other indirectly via the microwave photons on the microstrip line. Our works for the distant magnon-magnon coupling mediated by nonresonant photons might provide new sight into long-distant information transmission.

Signature of electromagnetic quantum fluctuations in exciton physics

Quantum fluctuations of the electromagnetic field are known to produce the atomic Lamb shift. We here reveal their iconic signature in semiconductor physics, through the blue-shift they produce to optically bright excitons, thus lifting the energy of these excitons above their dark counterparts. The electromagnetic field here acts in its full complexity: in addition to its longitudinal part via interband virtual Coulomb processes, the transverse part —which has been missed up to now— also acts via resonant and nonresonant virtual photons. These two parts beautifully combine to produce a bright exciton blue-shift independent of the exciton wave vector direction. Our work readily leads to a striking prediction: long-lived excitons must have a small bright-dark splitting. Although the analogy between exciton and hydrogen atom could lead us to see the bright exciton shift as a Lamb shift, this is not fully so: the Lamb shift comes entirely from virtual photons, whereas the Coulomb interaction also contributes to the exciton shift through the so-called “electron-hole exchange”.

Quantum dynamics of disordered arrays of interacting superconducting qubits: Signatures of quantum collective states

We study theoretically the collective quantum dynamics occurring in various interacting superconducting qubits arrays (SQAs) in the presence of a spread of individual qubit frequencies. The interaction is provided by mutual inductive coupling between adjacent qubits (short-range Ising interaction) or inductive coupling to a low-dissipative resonator (long-range exchange interaction). In the absence of interaction the Fourier transform of temporal correlation function of the total polarization ($z$-projection of the total spin), i.e. the dynamic susceptibility $C(\omega)$, demonstrates a set of sharp small magnitude resonances corresponding to the transitions of individual superconducting qubits. We show that even a weak interaction between qubits can overcome the disorder with a simultaneous formation of the collective excited states. This collective behavior manifests itself by a single large resonance in $C(\omega)$. In the presence of a weak non-resonant microwave photon field in the low-dissipative resonator, the positions of dominant resonances depend on the number of photons, i.e. the collective ac Stark effect. Coupling of an SQA to the transmission line allows a straightforward experimental access of the collective states in microwave transmission experiments and, at the same time, to employ SQAs as sensitive single-photon detectors.

Controllable photon extraction based on a single-photon Raman interaction

A target whispering-gallery-mode microresonator (WGMM) directly coupled to a waveguide with an auxiliary side-coupled WGMM is proposed to deterministically extract both the resonant and non-resonant single incident photons from a waveguide. Based on the single-photon Raman interaction (SPRINT) between an Λ-type three-level atom and the target WGMM, a full quantum theory in real space is adopted to calculate the extraction efficiencies at the single-photon level. The results show that the extraction efficiencies can be significantly improved by appropriately tuning the frequencies of the auxiliary WGMM and the coupling strength between the two WGMMs, even when the atom and WGMMs have dissipations. Since mode redistribution is only externally imposed on the auxiliary WGMM, the population and phase of the atom are not directly affected. The nonlocal control, which ensures that the SPRINT takes place, results in high extraction efficiencies. We also find that the transmission probabilities of both the resonant and non-resonant incident photons can be controlled in a range from 0 to 100%, so that the proposed double-WGMM system has the potential to be used as a single-photon switch.

Photon catalysis of deuterium iodide photodissociation.

A catalyst enhances a reaction pathway without itself being consumed or changed. Recently, there has been growing interest in the concept of "photon catalysis" in which nonresonant photons, which are neither absorbed nor scattered, promote reactions. The driving force behind this effect is the interaction between the strong electric field associated with a pulsed, focused laser and the polarizability of the reacting system. In this study, the effect of near-infrared, nonresonant radiation on the photodissociation of deuterium iodide is demonstrated. We use nanosecond pulses rather than time-resolved spectroscopy to investigate the average effect of the electric field on the branching ratio for forming D + I(2P3/2) and D + I(2P1/2). Changes in the measured D-atom speeds between field-free and strong-field conditions confirm substantial differences in dissociation dynamics. Both the magnitude and direction of change in the branching ratios are dependent upon the photodissociation wavelength. Experiments and theoretical calculations confirm that the mechanism for photon catalysis under these conditions is dynamic Stark shifting of potential energy surfaces rather than electric-field-induced alignment of reagent molecules.

Nonresonant Photons Catalyze Photodissociation of Phenol.

Phenol represents an ideal polyatomic system for demonstrating photon catalysis because of its large polarizability, well-characterized excited-state potential energy surfaces, and nonadiabatic dissociation dynamics. A nonresonant IR pulse (1064 nm) supplies a strong electric field (4 × 107 V/cm) during the photolysis of isolated phenol (C6H5OH) molecules to yield C6H5O + H near two known energetic thresholds: the S1/S2 conical intersection and the S1 - S0 origin. H-atom speed distributions show marked changes in the relative contributions of dissociative pathways in both cases, compared to the absence of the nonresonant IR pulse. Results indicate that nonresonant photons lower the activation barrier for some pathways relative to others by dynamically Stark shifting the excited-state potential energy surfaces rather than aligning molecules in the strong electric field. Theoretical calculations offer support for the experimental interpretation.

Neutralization of negative hydrogen and deuterium ion beams using non-resonance adiabatic photon trap

Experimental results on neutralization of negative ion beams in a photon stripping target are presented. For the energy of beams used in these studies (6–10 keV), the maximum neutralization efficiency is 95%. In contrast with gas or plasma neutralizers, the generation of positive ions from the negative ion beam was negligible. A non-resonance photon trap with highly reflecting mirrors of special shape was used as a stripping target. Due to a special mirror shape, in the process of photons reflections and propagation inside the trap there are some adiabatically conserved invariants that limits the volume accessible for photon motion even if the mirror surface is not closed. This approach makes it possible to overcome limitations typical for the Fabry–Perot cells, which require high radiation quality, high quality of the optical elements, and very high mechanical stability of the cell. The trap was pumped by commercially available fiber laser (λ = 1070 nm, Δλ = 7 nm, P = 2.1 kW) through a small hole in the mirror. The experiments were carried out with H- and D-beams. The observed neutralization efficiency depended mainly on the reflectivity of the mirrors, on defects on their surface, and on the laser pumping power.

Targeted photonic routers with chiral photon-atom interactions

The photonic router is a key device in optical quantum networks. Conventional routers, however, can only transfer a photon from the input port to the desired port probabilistically. Here, we propose to use chiral photon-atom interactions for targeted routing that can transfer a single photon from the input port to an arbitrarily selected output port deterministically, i.e., with $100%$ probability. The configuration of the proposed router consists of a driven three-level atom which is chirally coupled to two photonic waveguides simultaneously. It is shown that, by properly adjusting the driving field on the atom, a single photon inputting from one port of the first waveguide can be deterministically transferred to one of the selected output ports of the second waveguide. Both resonant and nonresonant photons can be deterministically routed to the desired ports. We also examine how the routing fidelity is influenced by dissipations and imperfections, and investigate the transmission characters of two resonant photons.

Controllable single-photon nonreciprocal propagation between two waveguides chirally coupled to a quantum emitter.

We investigate coherent controlling single-photon nonreciprocal propagation in a pair of waveguides chirally coupled to an atom by using a classical optical field. The results show that for a nonresonant photon, the perfect single-photon nonreciprocal propagation can be realized by adjusting the Rabi frequency and detuning. Furthermore, the nonreciprocal propagation is switchable by using the classic field. The calculated results also show that the system can be used as a frequency filter to filter out some special frequencies for single-photon nonreciprocal propagation. The influences of nonperfect chiral coupling and dissipations on the nonreciprocal propagation are also shown.

An experimental investigation of nonresonance photon accumulation in a system of spherical mirrors

A new, nonresonant approach to photon accumulation in a system of two spherical mirrors is demonstrated experimentally. A high accumulation coefficient is obtained experimentally, and sufficient efficiency of this technique for application in such areas as spectroscopy, photochemistry, and photon neutralization of negative-ion beams is demonstrated. The photon accumulation efficiency is determined mainly by mirror reflectivity. It is nearly independent of the quality of the coupled-in radiation and does not require very high precision in aligning optical elements. The experimentally obtained data agree with theoretical calculations.

Molecular photoelectron angular distribution rotations in multi-photon resonant ionization of H2(+) by circularly polarized ultraviolet laser pulses.

We study effects of pulse durations on molecular photoelectron angular distributions (MPADs) in ultrafast circular polarization ultraviolet resonant ionization processes. Simulations performed on aligned H2 (+) by numerically solving time dependent Schrödinger equations show rotations of MPADs with respect to the molecular symmetry axes. It is found that in multi-photon resonant ionization processes, rotation angles are sensitive to pulse durations, which we attribute to the coherent resonant excitation between the ground state and the intermediate excited electronic state induced by Rabi oscillations. Multi-photon nonresonant and single photon ionization processes are simulated and compared which exhibit a constant rotation angle. An asymmetry parameter is introduced to describe the pulse duration sensitivity by perturbation theory models. Influence of pulse frequency detunings on MPADs is also investigated where oscillations of rotations are absent at long pulse durations due to nonresonance excitation.

Non-resonant elastic scattering of low-energy photons by atomic sodium confined in quantum plasmas

The non-resonant elastic scattering of low-energy photons by the bound valence electron in the ground state 3s of atomic sodium confined in quantum plasmas is investigated theoretically. The incident photon energy is assumed to be much smaller than the 3s-3p excitation energy. The alkali atom sodium is first formulated as an effective one-electron problem in which the attractive interaction between the valence electron and the atomic ion core is simulated by a spherically symmetric model potential. The Shukla-Eliasson oscillatory exponential cosine screened-Coulomb potential model is then used to mimic the effective two-body (valence-core) interaction within quantum plasmas. Non-relativistic calculations performed within the electric dipole approximation indicate that the non-resonant elastic photon scattering cross-section undergoes a dramatic growth by several orders of magnitude as the quantum wave number increases. A qualitative explanation of this phenomenon is presented. In the absence of the oscillatory cosine screening term, a similar growth is observed at larger values of the quantum wave number. Our computed relevant atomic data are in very good agreement with the experimental as well as the previous theoretical data for the zero-screening (free atom) case, and with the very limited, accurate theoretical results available for the case of exponential screened-Coulomb two-body interaction, without the cosine screening term.

New results in high-resolution X-ray fluorescence spectroscopy

We present some recent results dealing with resonant inelastic X-ray scattering (RIXS) on atomic targets in the 3-5 keV enegy region. In this so-called tender spectral region, the K-shell fluorescence branching ratios become reasonably large, but a full vacuum enclosure is still preferable to avoid detection efficiency loss due to the sizeable arms of high resolution crystal spectrometers. By squeezing energy resolution in the fluorescence decay channel, one may improve the spectral resolution of photoabsorption, enable separation of multielectron excitation and relaxation channels, and completely eliminate the need to scan across the selected energy range of the photon probe in order to acquire the photoabsorption spectrum. On the other hand, the spectra may be untrivially modified by effects such as interference of absorption-emission paths or structured relaxation modes, and a more elaborated modelling is needed to understand the emitted signal. We illustrate these aspects by presenting four cases: the reconstruction of Ar KM and Ar KL absorption edges from a series of highly resolved emission spectra recorded at different probe energies, the reconstruction of the Xe L3 edge from a single X-ray emission spectrum, and the analysis of the radiative Ar K-MM Auger decay preceeded by the resonant or nonresonant photon absorption.

Possibility of giant enhancement of low-frequency non-resonant Rayleigh scattering by atomic systems within dense plasmas

In this paper, we demonstrate the possibility of electron density-induced giant growth of non-resonant Rayleigh scattering of electromagnetic radiation (in the low-frequency limit) by atomic systems within dense plasmas. Non-relativistic quantum mechanical calculation is performed under electric dipole approximation, for elastic scattering of radiation by the ground states 1s of plasma-embedded hydrogen-like atomic ions treated within the framework of the ion-sphere model. The results indicate giant enhancement of the non-resonant (photon frequency ω being much smaller than the lowest resonance frequency ω1s−2p) Rayleigh cross-section by an order of magnitude, at (atomic system-specific) high enough plasma electron densities under present consideration. The Z−8-scaling of the non-resonant Rayleigh cross-section in free and isolated H-isoelectronic sequence of ions is shown to be broken in dense plasma environments.

Accurate non-relativistic photoionization cross section for He at non-resonant photon energies

The total single-photon ionization cross section was calculated for helium atoms in their ground state. Using a full configuration-interaction approach the photoionization cross section was extracted from the complex-scaled resolvent. Our results agree with an earlier B-spline-based calculation in which the continuum is box discretized within a relative deviation of less than 0.06% in the energy range from 28 to 59 eV. On the other hand, above the He++ threshold our results agree very well to a recent Floquet calculation. Thus, our calculation confirms the previously reported deviations from the experimental reference data outside the claimed error estimate. In order to extend the calculated spectrum to very high energies, an analytical hydrogenic-type model tail is introduced that should become asymptotically exact for infinite photon energies. Its universality is investigated considering also H−, Li+ and HeH+. With the aid of the tail corrections to the dipole approximation are estimated.

Greatly enhanced absorption of nonresonant microwave fields by ultracold molecules near a Feshbach resonance

We show that the probability of the collision-induced absorption of nonresonant microwave photons by a gas of ultracold molecules is dramatically enhanced near a Feshbach scattering resonance. This can be used for detecting Feshbach resonances of ultracold molecules by measuring the microwave field absorption and for tuning the elastic scattering cross sections of ultracold molecules by varying the frequency and intensity of the microwave field in a wide range of the field parameters.

Time-dependent analysis of few-photon coherent control schemes

We investigate the coherent control of nonresonant two-photon excitation and ($2+1$) photon ionization processes from the time-dependent perspective. To this end, we have solved the time-dependent Schr\"odinger equation for a hydrogen atom interacting with an ultraviolet laser field. Results are obtained for symmetric and antisymmetric phase distributions leading to dark and bright pulses, for which the temporal field distributions consist of many subpulses. For the two-photon excitation process, it is found that at intermediate time between the subpulses, the population in the excited state can exceed the final state population and, in particular, is nonzero for dark pulses. The results for the ($2+1$) photon ionization closely follow those for the excitation process, which shows that the ionization of the electron proceeds as a resonant process via the excited state in all cases considered.

Statistical analysis and digital processing of the Mössbauer spectra

This work is focused on using the statistical methods and development of the filtration procedures for signal processing in Mössbauer spectroscopy. Statistical tools for noise filtering in the measured spectra are used in many scientific areas. The use of a pure statistical approach in accumulated Mössbauer spectra filtration is described. In Mössbauer spectroscopy, the noise can be considered as a Poisson statistical process with a Gaussian distribution for high numbers of observations. This noise is a superposition of the non-resonant photons counting with electronic noise (from γ-ray detection and discrimination units), and the velocity system quality that can be characterized by the velocity nonlinearities. The possibility of a noise-reducing process using a new design of statistical filter procedure is described. This mathematical procedure improves the signal-to-noise ratio and thus makes it easier to determine the hyperfine parameters of the given Mössbauer spectra. The filter procedure is based on a periodogram method that makes it possible to assign the statistically important components in the spectral domain. The significance level for these components is then feedback-controlled using the correlation coefficient test results. The estimation of the theoretical correlation coefficient level which corresponds to the spectrum resolution is performed. Correlation coefficient test is based on comparison of the theoretical and the experimental correlation coefficients given by the Spearman method. The correctness of this solution was analyzed by a series of statistical tests and confirmed by many spectra measured with increasing statistical quality for a given sample (absorber). The effect of this filter procedure depends on the signal-to-noise ratio and the applicability of this method has binding conditions.