Three-level V-type Atomic System Research Articles

Goos–Hänchen shifts in a V-type three-level atomic system interacting with squeezed vacuum

This study explores the Goos–Hänchen (GH) shift phenomenon within a cavity hosting a V-type three-level atomic system, engaged with two independent broadband squeezed baths. Our exploration encompasses a thorough analysis of the lateral shifts in both reflected and transmitted light beams, with a focus on the impact of critical factors, i.e, coupling field strength, incoherent pumping field strength, and squeezed vacuum intensity. Our results reveal an interplay of these parameters, resulting in distinctive negative and positive GH shifts in both reflected and transmitted light. In addition, a remarkable enhancement of GH shifts at specific angles of incidence is observed, presenting a wide-ranging modulation across diverse system parameters. This study not only enriches the understanding of the GH shift in complex atomic systems but also highlights the potential for the manipulation of these lateral shifts by fine-tuning key variables of the system, and contributes valuable insights to the broader field of optical phenomena in quantum systems.

Controllable optical bistability and multistability in a V-type three-level atomic system interacting with two broadband independent squeezed baths

In this study, we investigate the optical bistability (OB) and optical multistability (OM) phenomena within a V-type three-level atomic system interacting with two independent broadband squeezed baths confined in a unidirectional cavity. Our analysis reveals that the transition between OB and OM is influenced by the strength of the control field and the intensity of the squeezed vacuum. Notably, the impact of each of these factors on the transition exhibits distinct characteristics. Furthermore, we explore the effects of additional system parameters, such as the incoherent pumping rate and cooperation parameter. Our findings emphasize the crucial roles played by these parameters in shaping the observed results. Specifically, we observe that variations in the incoherent pumping rate and cooperation parameter contribute significantly to the system’s OB and OM behavior, further underscoring the multifaceted nature of the studied atomic system. This comprehensive investigation not only elucidates the intricate interplay between key parameters but also unveils the sensitivity of the system to variations in control field strength, intensity of the squeezed vacuum, incoherent pumping rate, and cooperation parameter.

Analytical solutions for susceptibility in electromagnetically induced transparency in a Doppler-broadened V-type three-level atomic system

Herein, we present accurate analytical solutions for susceptibility in electromagnetically induced transparency in a Doppler-broadened V-type three-level atomic system, up to the first (arbitrary) order of the Rabi frequency in a probe (coupling) beam. The directions of the coupling and probe beams are either parallel or anti-parallel. The susceptibility is averaged over a Maxwell–Boltzmann velocity distribution, and decomposed into three terms: background, hole-burning, and coherence. Furthermore, the effects of the openness of the system, propagation direction of the laser beams, and ratio of the wavelengths on the coherence contribution of the susceptibility are presented.

Observation of Vacuum-Induced Collective Quantum Beats.

We demonstrate collectively enhanced vacuum-induced quantum beat dynamics from a three-level V-type atomic system. Exciting a dilute atomic gas of magneto-optically trapped ^{85}Rb atoms with a weak drive resonant on one of the transitions, we observe the forward-scattered field after a sudden shut-off of the laser. The subsequent radiative dynamics, measured for various optical depths of the atomic cloud, exhibits superradiant decay rates, as well as collectively enhanced quantum beats. Our work is also the first experimental illustration of quantum beats arising from atoms initially prepared in a single excited level as a result of the vacuum-induced coupling between excited levels.

Effective control and switching of optical multistability in a three-level V-type atomic system

We theoretically analyze the behavior of single optical bistability (OB), double OB, and tristability (OT) in a three-level V-type atomic system confined in a unidirectional optical ring cavity. The physics behind the emergence of various bistable and tristable states, and switching from the absorptive to the dispersive characteristics, are explored. The role of probe- and control-field detunings on the input-output characteristics is probed. Further, it is found that the switching between various bistable phenomena is defined by the ratio between the absolute peak values of the parameters describing dispersion and absorption, respectively. This ratio sets a criterion for obtaining absorptive OB, OT, double OB, and dispersive OB. The role of control-field intensity and detuning as well as the cooperation parameter on the input-output characteristics are explored. Finally, a scheme is discussed to control the width of the middle branch of double OB and OT as well as single OB.

Orbital angular momentum transfer via spontaneously generated coherence

We study the orbital angular momentum (OAM) transfer from a weak Laguerre–Gaussian (LG) field to a weak plane wave in two closed-loop three-level V-type atomic systems. In the first scheme, the atomic system has two non-degenerate upper levels where the corresponding transition is excited by a microwave plane wave. It is analytically shown that the microwave field induces an OAM transfer from an LG field to a generated third field. It is demonstrated that the efficiency of the OAM transfer decreases when the thermal velocity distribution of atoms is considered. In the second scheme, we consider a three-level V-type atomic system with two near-degenerate excited states and study the effect of the quantum interference due to the spontaneous emission on the OAM transfer. It is found that spontaneously generated coherence (SGC) induces the OAM transfer from the LG field to the weak planar field, and the OAM transfer does not occur in the absence of the SGC. The suggested models offer a rather simple method for the OAM transfer that can be used in quantum information processing and data storage.

All-optical switching and flip-flop based on dynamically controlled bistability in a V-type atomic system

We have proposed a scheme for all-optical switching and flip-flop based on controllable optical bistability in a simple three-level V-type atomic system assisted by an incoherent pump field. Due to the auxiliary incoherent pump, the atomic population is redistributed in the three levels, and then the absorption-dispersion property and the Kerr nonlinearity of the medium are different from those of the conventional V-type electromagnetically induced transparency system. The results show that both the thresholds and the area (or shape) of the hysteresis loop can be controlled efficiently via the adjustment of either the incoherent pump field or the coupling field. As a result, with a constant cavity input, the output of the optical cavity can be switched between the low- and high-power states of different bistable curves by tuning the optical fields. Based on this effect, we realize all-optical steady-state switching and set-reset flip-flop operation by adding a pulse sequence (positive pulse or set-reset pulse) onto either the incoherent pump field or the coupling field. Such a simple and effective technique of optical switching and flip-flop can find application in all-optical signal processing systems.

Measurement of quantum defect of cesium nP<sub>3/2</sub> (n = 70—94) Rydberg states by using ultraviolet single-photon Rydberg excitation

A narrow-linewidth continuous-wave single-frequency tunable 318.6-nm ultraviolet laser system with watt-level output power is developed in our experiment based on well-developed fiber lasers, fiber amplifiers, and efficient laser frequency conversion technique. Cesium 6S<sub>1/2</sub>—<i>n</i>P<sub>3/2</sub> (<i>n</i> = 70—94) single-photon Rydberg excitation in a room-temperature cesium atomic vapor cell is realized by using our ultraviolet laser system. The single-photon Rydberg excitation signal is obtained via the V-type three-level atomic system which contains 6S<sub>1/2</sub> (<i>F</i> = 4) ground state, 6P<sub>3/2</sub> (<i>F</i> = 5) excited state and one of <i>n</i>P<sub>3/2</sub> (<i>n</i> = 70—94) Rydberg states. When cesium atoms populated on the ground state are partially excited to Rydberg state by the ultraviolet laser, absorption of 852.3-nm probe beam which is locked to 6S<sub>1/2</sub> (<i>F</i> = 4)—6P<sub>3/2</sub> (<i>F</i> ′ = 5) hyperfine transition will decrease. In this way, the cesium Rydberg states are detected. The quantum defects for cesium <i>n</i>P<sub>3/2</sub> (<i>n</i> = 70—94) Rydberg states are experimentally measured with a high-precision wavemeter. The variation trend of experimentally measured data deviates from that of calculated values. Due to the fact that the cesium vapor cell is positioned in a magnetic shielding tank, the Zeeman effect can be ignored. Considering that the polarizability of Rydberg atoms is proportional to (<i>n</i>*)<sup>7</sup>, in which <i>n</i>* is the effective principal quantum number, the Rydberg screen effect of cesium atomic vapor cell cannot completely protect cesium atoms from being perturbed by an external DC electric field. Therefore the residual DC electric field existing inside the cesium vapor cell will have a significant influence on quantum defect measurement of Rydberg atoms. Using the theoretical model of Stark effect and the relationship between polarizability of Rydberg atoms and the effective principal quantum number <i>n</i>*, the corrected experimental value of quantum defect for cesium <i>n</i>P<sub>3/2</sub> (<i>n</i> = 70—94) Rydberg states is found to be ~(3.5591 ± 0.0007). The corrected experimental value of quantum defect is consistent with the calculation.

Coherence effects in electromagnetically induced transparency in V-type systems of 87Rb.

We present a theoretical and experimental study of electromagnetically induced transparency (EIT) in V-type systems of 87Rb atoms. We calculate accurate lineshapes of V-type EIT spectra by solving density matrix equations considering all the magnetic sublevels involved. The calculated spectra demonstrate consistency with the experimental results. We identify the coherence effect in the calculated EIT spectra, and determine that the coherence effect exists only in the cycling transition. We explain the reason for the suppression of the coherence effect in open transitions using an analytical calculation of the spectra for a simple V-type three-level atomic system.

Effect of two-qutrit entanglement on quantum speed limit time of a bipartite V-type open system

In the present paper, quantum speed limit (QSL) time of a bipartite V-type three-level atomic system under the effect of two-qutrit entanglement is investigated. Each party interacts with own independent reservoir. By considering two local unitarily equivalent Werner states and the Horodecki PPT state, as initial states, the QSL time is evaluated for each of them in the respective entangled regions. It is counterintuitively observed that the effect of entanglement on the QSL time driven from each of the initial Werner states are completely different when the degree of non-Markovianity is considerable. In addition, it is interesting that the effect of entanglement of the non-equivalent Horodecki state on the calculated QSL time displays an intermediate behavior relative to the cases obtained for the Werner states.

All-optical switching in an open V-type atomic system

In this paper, the optical bistability (OB) and absorption properties of a weak probe field in an open V-type three-level atomic system have been investigated. We found that the OB threshold could be reduced via spontaneously generated coherence (SGC), coherent and incoherent pump fields, atomic injection, and exit rates. We also found that the threshold intensity of OB in an open system was less than that in the closed system. The all-optical switching due to the OB has also been discussed.

Atom–photon entanglement beyond the multi-photon resonance condition

Atom---photon entanglement between the dressed atom and its spontaneous emission is studied in a near-degenerate three-level V-type atomic system in multi-photon resonance condition and beyond it. Taking into account the quantum interference due to the spontaneous emission, the density matrix equations of motion are numerically calculated in two-photon resonance condition and beyond it. The dynamical behavior of these two subsystems is investigated by using the von Neumann entropy. We apply the Floquet decomposition to the equations of motion to solve this time-dependent problem and identify the contribution of the different scattering processes to the atom---photon entanglement. In addition, the impact of the various nonlinear effects on the atom---photon entanglement is introduced in two-photon resonance condition. It is shown that the degree of entanglement (DEM) can be controlled via the intensity and the detuning of the coupling field as well as the quantum interference induced by spontaneous emission. We find that vacuum-induced interference has a major role in phase sensitivity of the DEM; however, beyond the two-photon resonance condition the DEM does not depend on the relative phase of the applied fields. Our results can be used for quantum information processing via entanglement.

V型三能级原子系统中电磁诱导各向同性的二维左手效应

V型三能级原子系统中电磁诱导各向同性的二维左手效应

Effect of Spontaneously Generated Coherence and Detuning on 2D Atom Localization in Two Orthogonal Standing-Wave Fields

Two-dimensional (2D) atom localization via the spontaneously generated coherence (SGC) and detunings associated with the probe and standing-wave driving fields in a three-level V-type atomic system are investigated. In the gain process, two equal and tunable peak maxima of position distribution in the x—y plane via the detunings are observed. However, one decreasing and the other increasing peak maxima in the absorption process via the SGC are achieved in the quadrants I and III of the x—y plane. A better resolution and more novelty for the 2D atom localization in our scheme are obtained.

Microwave-induced coherence effects in refractive index of a V-type three-level atom

A V-type three-level atomic system driven by a coherent field and a microwave field is considered. In this kind of model, the creation of upper level coherence does not require non-orthogonal dipoles. It is found that due to the microwave-induced coherence, refraction–absorption properties can be controlled by the relative phase of applied fields, and high refractive index without absorption can be always achieved just by choosing proper values of the relative phase.

Role of strongly modulated coherence in transient evolution dynamics of probe absorption in a three-level atomic system

We investigate the dynamical behaviour of atomic response in a closed three-level V-type atomic system with the variation of different relevant parameters to exhibit transient evolution of absorption, gain and transparency in the probe response. The oscillations in probe absorption and gain can be efficiently modulated by changing the values of the Rabi frequency, detuning and the collective phase involved in the system. The interesting outcome of the work is the generation of coherence controlled loop-structure with varying amplitudes in the oscillatory probe response of the probe field at various parameter conditions. The prominence of these structures is observed when the coherence induced in a one-photon excitation path is strongly modified by two-step excitations driven by the coherent fields operating in closed interaction contour. In contrast to purely resonant case, the time interval between two successive loops gets significantly reduced with the application of non-zero detuning in the coherent fields.

Self-calibrating tomography for multidimensional systems

We present a formalism for self-calibrating tomography of arbitrary dimensional systems. Self-calibrating quantum state tomography was first introduced in the context of qubits, and allows the reconstruction of the density matrix of an unknown quantum state despite incomplete knowledge of the unitary operations used to change the measurement basis. We show how this can be generalized to qudits, i.e. d-level systems, and provide a specific example for a V-type three-level atomic system whose transition dipole moments are not known. We show that it is always possible to retrieve the unknown state and process parameters, except for a set of zero measure in the state-parameter space.

Birefringence enhancement via quantum interference in the presence of a static magnetic field

We investigate the effect of quantum interference due to the spontaneous emission on the linear magneto-optical rotation (MOR) in the V-type three-level atomic system. It is shown that, in the presence of a static magnetic field, the vacuum induced coherence can enhance birefringence via the Macaluso–Corbino effect. Moreover, it is demonstrated that the Doppler effect due to the motion of atoms plays a destructive role in the linear MOR. Our results show that birefringence enhancement due to spontaneously generated coherence (SGC) does not appear in the Λ-type three-level atomic system.

Amplitude and phase control of transient absorption and dispersion in a microwave-driven atomic system

In a V-type three-level atomic system driven by a coherent field and a microwave field, we exploit the fact that the transient absorption and dispersion properties of the probe laser can be dramatically modified by controlling the relative phase of the applied fields. With proper values of the relative phase, the transient absorption can be eliminated, and the high refractive index without absorption can be achieved. It is shown that amplitude of the microwave field is also important factor that can result in different gain and dispersion behaviors of the probe.

Plasmonic effects in excitonic population transfer in a driven semiconductor–metal nanoparticle hybrid system

We have investigated the coherent transfer of excitonic populations in a semiconductor quantum dot (SQD) modulated by the surface plasmon of a metallic nanoparticle (MNP). The SQD is considered as a three-level V-type atomic system. We applied a transform-limited laser pulse field resonant with the upper atomic levels of the SQD. When the SQD is close enough to the MNP, the otherwise equally populated atomic levels can be selectively excited. Selectivity population can be achieved by two physical mechanisms: an enhancement of the Rabi frequencies that drive the optical transitions, which depends on the polarization arrangement, and a frequency shift of the optical transitions that leads to a dynamical detuning.