Showing papers on "Atomic coherence published in 2003"
TL;DR: In this paper, a quantum Carnot engine with quantum coherence was proposed, in which the atoms in the heat bath were given a small bit of quantum co-herence, which can be used to increase the temperature of the radiation field and to extract work from a single heat bath.
Abstract: We present here a quantum Carnot engine in which the atoms in the heat bath are given a small bit of quantum coherence. The induced quantum coherence becomes vanishingly small in the high-temperature limit at which we operate and the heat bath is essentially thermal. However, the phase φ, associated with the atomic coherence, provides a new control parameter that can be varied to increase the temperature of the radiation field and to extract work from a single heat bath. The deep physics behind the second law of thermodynamics is not violated; nevertheless, the quantum Carnot engine has certain features that are not possible in a classical engine.
606 citations
TL;DR: Optical multistability in an optical ring cavity filled with a collection of three-level Lambda-type rubidium atoms has been experimentally demonstrated and is very sensitive to the induced atomic coherence in the system.
Abstract: Optical multistability in an optical ring cavity filled with a collection of three-level Lambda-type rubidium atoms has been experimentally demonstrated. The observed multistability is very sensitive to the induced atomic coherence in the system and can evolve from a normal bistable behavior with the change of the coupling field as well as the atomic number density. The underlying mechanism for the formation of such multistability is also discussed.
209 citations
TL;DR: In this paper, the optical bistability of an optical ring cavity filled with a collection of three-level $\ensuremath{\Lambda}$-type rubidium atoms, interacting with two collinearly propagating laser beams, was investigated.
Abstract: We have experimentally studied the optical bistable behavior in an optical ring cavity filled with a collection of three-level $\ensuremath{\Lambda}$-type rubidium atoms, interacting with two collinearly propagating laser beams. The bistability so observed is very sensitive to the induced atomic coherence in this electromagnetically induced transparency system or consequently to the altered nonlinearity in the system and, thus, can easily be controlled by changing the intensity and the frequency detuning of the coupling field.
190 citations
TL;DR: Coherent quantum bit operations along with quantum state transport open the route towards a "quantum shift register" of individual neutral atoms, which preserves the atomic coherence with slight reduction of coherence time.
Abstract: We have prepared and detected quantum coherences of trapped cesium atoms with long dephasing times. Controlled transport by an "optical conveyor belt" over macroscopic distances preserves the atomic coherence with slight reduction of coherence time. The limiting dephasing effects are experimentally identified, and we present an analytical model of the reversible and irreversible dephasing mechanisms. Our experimental methods are applicable at the single-atom level. Coherent quantum bit operations along with quantum state transport open the route towards a "quantum shift register" of individual neutral atoms.
140 citations
TL;DR: It is shown that the effect results in a modification of the nonlinear Faraday rotation of light propagating in an 87Rb vapor cell by changing the ellipticity of the light.
Abstract: We propose a new method of resonant enhancement of optical Kerr nonlinearity that uses multilevel atomic coherence. The enhancement is accompanied by suppression of the other linear and nonlinear susceptibility terms of the medium. We show that the effect results in a modification of the nonlinear Faraday rotation of light propagating in an Rb87 vapor cell by changing the ellipticity of the light.
102 citations
TL;DR: Light carrying orbital angular momentum is generated via an electromagnetically induced Zeeman coherence grating in cold cesium atoms, which constitutes a first step towards the processing of quantum information encoded in a multidimensional state space.
Abstract: We report on the generation of light carrying orbital angular momentum through Bragg diffraction into an electromagnetically induced coherence grating in a degenerate two-level system of cold cesium atoms. The induced Zeeman coherence grating is shown to contain the spatial phase structure of the incident beams. The exchange of phase information between a light beam with orbital angular momentum and a long-lived atomic coherence opens up the way to process quantum information encoded in a multidimensional state space.
83 citations
TL;DR: In this paper, spontaneous emission can create coherence in a ladder-type three-level atom with equispaced levels, subject to the condition that the atomic dipole moments are nonorthogonal.
41 citations
TL;DR: In this article, an ellipticity-dependent nonlinear magneto-optic rotation of elliptically polarized light propagating in a medium with atomic coherence was shown to be associated with an enhancement of Kerr and higher-order nonlinearities accompanied by suppression of the other linear and nonlinear susceptibility terms.
Abstract: We predict theoretically and demonstrate experimentally an ellipticity-dependent nonlinear magneto-optic rotation of elliptically polarized light propagating in a medium with atomic coherence. We show that this effect results from hexadecapole and higher-order moments of the atomic coherence, and is associated with an enhancement of Kerr and higher-order nonlinearities accompanied by suppression of the other linear and nonlinear susceptibility terms of the medium. These nonlinearities might be useful for quantum signal processing. In particular, we report an observation of enhancement of the polarization rotation of elliptically polarized light resonant with the ${5S}_{1/2}F=\stackrel{\ensuremath{\rightarrow}}{2}{5P}_{1/2}F=1$ transition of ${}^{87}\mathrm{Rb}.$
41 citations
TL;DR: In this article, the influence of the local field correction (LFC) on the optical behavior of a closed V-type system was investigated, and it was shown that the system can switch between absorption and gain by controlling the near dipole-dipole parameter.
Abstract: In this paper we investigate the influence of the local field correction (LFC) on the optical behavior of a closed V-type system. We consider a V configuration such that quantum interference between the two decay channels to the ground atomic level is important. When the two optical transitions are coupled by one laser field we find that LFC does not destroy the non-absorption resonance that usually appears due to quantum interference. On the other hand, the absorption profile is deformed due to the presence of LFC. We have also studied the case of a driving laser field coupling one of the optical transitions, and a probe laser field coupling the other one. In this field configuration the local field modifies substantially the optical response. We have found that the system can switch between absorption and gain by controlling the near dipole-dipole parameter. On the other hand, the relative phase between the pump and probe fields allow us to change the system from absorption to gain.
35 citations
TL;DR: In this article, a four-level atomic system with two closely lying upper levels driven by two coherent fields is considered, and it is shown that, in the presence of a weak incoherent pump, steady-state gain can be achieved as a result of quantum interference from spontaneous emission.
Abstract: A four-level atomic system with two closely lying upper levels driven by two coherent fields is considered. We show that, in the presence of a weak incoherent pump, steady-state gain can be achieved as a result of quantum interference from spontaneous emission. The gain depends on the relative phase between the two fields, so it can be modulated by control of the relative phase. Also, by controlling the relative phase, one can always obtain a large index of refraction with zero absorption.
27 citations
TL;DR: In this paper, a two-level system with a strong standing wave was examined by the probe field resonant to the adjacent transition in the $\ensuremath{\Lambda}$ configuration of Ar II.
Abstract: The interaction of a two-level system with a strong standing wave is examined by the probe field resonant to the adjacent transition in the $\ensuremath{\Lambda}$ configuration of Ar II. The known peak of electromagnetically induced transparency is observed in the absorption spectrum at the detuning of the probe field proportional to the detuning of the strong field. Along with it, the different structure has been found at the line center, independently of the strong-field frequency. The calculations clarify that the central structure is induced by the higher-order spatial harmonics of the atomic coherence induced at the probe transition. The effect results in steep frequency dependence of the refractive index at the line center.
TL;DR: In this article, the effects of spontaneous coherence on the transient process in the presence of a weak probe and a strong coherent field were investigated, and it was shown that the transient gain can be greatly enhanced due to the spontaneous emission, and the transient absorption can be almost eliminated just by choosing the proper relative phase between the two fields.
TL;DR: In this article, an experiment on Ramsey interferometry of the 37S 1/2 → 37P 1 /2 microwave transition in sodium Rydberg atoms has been performed.
Abstract: An experiment on Ramsey interferometry of the 37S1/2 → 37P1/2 microwave transition in sodium Rydberg atoms has been performed. Interaction of Rydberg atoms with a cw microwave radiation was effectively controlled by a pulse of weak (<1 V cm−1) electric field, that manipulated the transition frequency near 70 050 MHz. The pulse detuned the microwave radiation from exact resonance, and induced additional phases to the wavefunctions of Rydberg states due to the quadratic Stark shifts. As a result, the Ramsey fringes were observable both on scanning the frequency of the microwave field and on scanning the strength of the electric field pulse. The experiment confirmed that this Stark-switching technique provides a fast and effective control of the atom–light interactions, and preserves the atomic coherence. Possible applications of this technique to experiments on quantum computers are discussed.
TL;DR: In this article, the authors present an evaluation of the frequency shifts in an optically pumped caesium-beam frequency standard caused by the neighbouring transitions and show that the relative contributions of the Rabi and Ramsey pulling effects crucially depend on the quality of optical pumping.
Abstract: We present an evaluation of the frequency shifts in an optically pumped caesium-beam frequency standard caused by the neighbouring transitions. We analyse the shifts caused by the Rabi and Ramsey pulling effects and find a well-known result for the Rabi pulling but a new result for the Ramsey pulling. The revised Ramsey shift is found to be proportional to not the imaginary but the real part of the ground-state atomic coherence. The value of the Ramsey shift is proportional to the first power of the Rabi frequency defined by a small orthogonal component of the microwave field and the inverse value of the Zeeman splitting. We compare the shifts caused by the neighbouring transitions and show that the relative contributions of the Rabi and Ramsey pulling effects crucially depend on the quality of optical pumping. We estimate that the Rabi shift for the KRISS-1 caesium-beam frequency standard is at a relative level of 10−14 while the Ramsey shift is at a relative level of 10−12.
TL;DR: In this paper, the absorption and dispersion properties of a weak probe field monitoring a two-level atom driven by a trichromatic field were investigated and it was shown that the system can produce a number of multilevel coherence effects for atoms composed of three and more energy levels.
TL;DR: In this paper, the authors showed that the linewidth of the sub-Doppler absorption peak becomes narrower while the frequency detuning of coupling laser increases, in agreement with the theoretical prediction by G. Vemuri et al.
Abstract: Thanks to the atomic coherence in coupling laser driven atomic system, sub-Doppler absorption has been observed in Doppler-broadened cesium vapor cell via the /Lambda-type three-level scheme. The linewidth of the sub-Doppler absorption peak become narrower while the frequency detuning of coupling laser increases. The results are in agreement with the theoretical prediction by G. Vemuri et al.[PRA,Vol.53(1996) p.2842].
TL;DR: In this article, a general formalism of a three-level atom single-mode system by including arbitrary forms of nonlinearities of both the field and the intensity-dependent atom-field coupling is proposed.
Abstract: A general formalism of a three-level atom single-mode system by including arbitrary forms of nonlinearities of both the field and the intensity-dependent atom–field coupling is proposed. With an arbitrary initial condition, an exact analytical time-dependent solution is presented. The work here extends previous studies in this context. Under the condition of an initial coherent field, the atomic-level occupation probability shows the collapse–revival phenomena, which have different features with different forms of the nonlinearities. We derive an expression for the Pancharatnam phase for the entangled state of the system. It is shown that the Pancharatnam phase explicitly contains information about the statistics of the field and atomic coherence. Also, the influences of the nonlinearities on the squeezing phenomenon and the correlation functions are examined.
TL;DR: In this article, the authors show the advantages of a coupling scheme involving maximum coherence and demonstrate how a large atomic coherence between a ground and an highly excited state can be prepared by SCRAP.
Abstract: Four-wave mixing in resonant atomic vapors based on maximum coherence induced by Stark-chirped rapid adiabatic passage (SCRAP) is investigated theoretically. We show the advantages of a coupling scheme involving maximum coherence and demonstrate how a large atomic coherence between a ground and an highly excited state can be prepared by SCRAP. Full analytic solutions of the field propagation problem taking into account pump field depletion are derived. The solutions are obtained with the help of an Hamiltonian approach which in the adiabatic limit permits to reduce the full set of Maxwell-Bloch equations to simple canonical equations of Hamiltonian mechanics for the field variables. It is found that the conversion efficiency reached is largely enhanced if the phase mismatch induced by linear refraction is compensated. A detailed analysis of the phase matching conditions shows, however, that the phase mismatch contribution from the Kerr effect cannot be compensated simultaneously with linear refraction contribution. Therefore, the conversion efficiency in a coupling scheme involving maximum coherence prepared by SCRAP is high, but not equal to unity.
TL;DR: In this paper, the authors investigated atomic coherence changes caused by optical pumping applied to electromagnetically induced absorption (EIA) occurring at the open system, which consists of the transition between the Fg = 2 ground state and the Fe = 3 excited state in the 85Rb D1-line.
Abstract: We have investigated atomic coherence changes caused by optical pumping applied to electromagnetically induced absorption (EIA) occurring at the open system, which consists of the transition between the Fg = 2 ground state and the Fe = 3 excited state in the 85Rb D1-line. For optical pumping, another laser resonantly tuned to the transition between the Fg = 3 ground state and the Fe = 2 excited state was used. We found that the atomic coherence for EIA can be changed not by increasing the pumping rate but by pumping differently populations into the Zeeman sublevels in the Fg = 2 ground state, which is realized by changing the polarization of the pumping laser. The experimental results were able to be analysed by density matrix equations in the simple model system.
TL;DR: In this paper, the role of singularity/smoothness of density of modes (DOM) has been analyzed and a high-Q defect mode can induce perfect coherent population trapping.
TL;DR: In this paper, a four-level atomic model for light amplification at a short wavelength was proposed, where direct incoherent pumping into the top level is avoided by the advantage of coherent pumping.
Abstract: We propose a new four-level atomic model for achieving light amplification at a short wavelength, where direct incoherent pumping into the top level is avoided by the advantage of coherent pumping. In this model, the lower level of the probe transition is an excited state but not the usual ground state. By analytical as well as numerical calculations, we find that the probe gain, either with or without population inversion, which depends on the relation between spontaneous decay rates γ42 and γ21, can be achieved with proper parameters. We note that the Raman scattering gain always plays an important role in achieving the probe amplification.
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TL;DR: In this paper, the effects of detuning, Stark shift and atomic coherence on atomic dipole squeezing (ADS) were investigated in a two-mode system that consists of a twolevel atom interacting with a twomode quantized electromagnetic field, which is initially prepared in an entangled twomode coherent state via a nondegenerate two-photon process in a lossless cavity.
Abstract: Two-mode quantized electromagnetic fields can be entangled and admit a large number of coherent states. In this paper, we consider a two-mode system that consists of a two-level atom interacting with a two-mode quantized electromagnetic field, which is initially prepared in an entangled two-mode coherent state, via a nondegenerate two-photon process in a lossless cavity. We study the quantum fluctuations in the two-mode system and investigate in detail the effects of detuning, Stark shift and atomic coherence on atomic dipole squeezing (ADS). We show that ADS strongly depends on the atomic coherence. It is found that the stronger the correlations between the two modes are involved, the more the ADS could be generated. The detuning or Stark shift has a destructive effect on ADS, but the combined effect of the detuning and Stark shift may lead to a regular, periodical and strong ADS pattern.
TL;DR: In this article, the effects of detuning, Stark shift and atomic coherence on atomic dipole squeezing (ADS) were investigated in a two-mode system that consists of a twolevel atom interacting with a twomode quantized electromagnetic field, which is initially prepared in an entangled twomode coherent state via a nondegenerate two-photon process in a lossless cavity.
Abstract: Two-mode quantized electromagnetic fields can be entangled and admit a large number of coherent states. In this paper, we consider a two-mode system that consists of a two-level atom interacting with a two-mode quantized electromagnetic field, which is initially prepared in an entangled two-mode coherent state, via a nondegenerate two-photon process in a lossless cavity. We study the quantum fluctuations in the two-mode system and investigate in detail the effects of detuning, Stark shift and atomic coherence on atomic dipole squeezing (ADS). We show that ADS strongly depends on the atomic coherence. It is found that the stronger the correlations between the two modes are involved, the more the ADS could be generated. The detuning or Stark shift has a destructive effect on ADS, but the combined effect of the detuning and Stark shift may lead to a regular, periodical and strong ADS pattern.
TL;DR: In this paper, the authors investigated whether the laser-induced atomic coherence effect of electromagnetically induced transparency (EIT) could enhance the intensity of the EUV light generated.
Abstract: The generation of tunable, nanosecond-pulsed extreme-ultraviolet (EUV) light $(84.92\mathrm{nm}$ to $84.97\mathrm{nm}$ $\ensuremath{\sim}14.6\mathrm{eV})$ using four-wave mixing in optically deep krypton gas was investigated experimentally and theoretically. The sum-frequency mixing scheme generated light from two overlapping autoionizing resonances, ${17s}^{\ensuremath{'}}$ and ${15d}^{\ensuremath{'}}$. We investigated whether the laser-induced atomic coherence effect of electromagnetically induced transparency (EIT) could enhance the intensity of the EUV light generated. The maximum EUV output was seen from the region where the ${15d}^{\ensuremath{'}}$ autoionizing resonance has a transparency window due to Fano-type quantum interference. An analytical model using appropriate atomic parameters explains how background absorption can prevent EIT enhancement of EUV generation; and shows how a background Raman-like coupling term in the nonlinear susceptibility can well describe the measured EUV generation spectrum.
TL;DR: In this paper, the authors investigated HOADS in a high-Q micromaser cavity, where the atom interacts with the optical field via a multi-photon transition process and the initial atom is arbitrarily prepared.
Abstract: In our preceding serial works, we have investigated the generation of higher-order atomic dipole squeezing (HOADS) in a high-Q micromaser cavity, discussing the effects of dynamic Stark shift, atomic damping, atomic coherence and nonlinear one-photon processes and different initial states (for example, correlated and uncorrelated states, superposition states, squeezed vacuum). In this paper, we continue to study HOADS in a high-Q micromaser cavity, but consider that the atom interacts with the optical field via a multi-photon transition process and that the initial atom is arbitrarily prepared. For a vacuum initial field, we demonstrate that HOADS cannot occur if the atom is initially prepared in a chaotic state and that a coherent atomic state generates less efficient and stable HOADS than an arbitrary one. It is found that large detuning may lead to enhanced and strong HOADS.
TL;DR: In this article, the authors studied resonance fluorescence in a four-level ladder system and illustrate some novel features due to quantum interference and atomic coherence effects, and they found that under three photon resonant conditions, in some region of the parameter space of the rabi frequencies Ω 1, Ω 2, Ω 3, emission is dominantly by the level 4 at the line center even though there is an almost equal distribution of populations in all the levels.
TL;DR: In this article, a four-level system where a metastable state is included in an $Er −3＋}$ Doped Yttrium aluminum garnet (YAG) crystal was constructed.
Abstract: We construct a four-level system where a metastable state is included in an $Er^{3＋}$ Doped Yttrium aluminum garnet (YAG) crystal. Because of the action of the coherent field, the traditional light amplification with inversion can be exhibited with remarkable variation. As a result, we propose a method to achieve the gain equalization by atomic coherence. At the same time, we find that the high index of refraction accompanied by vanishing absorption can also be reached in this model. We also find that a higher index of refraction with zero absorption can be easily obtained when the coherent field is off resonance.
TL;DR: In this paper, the authors investigated the quantum dynamics and statistics of a double-well Bose-Einstein condensate with photo-association via left-well atoms tunnelling from initial right-well atomic condensates, which holds the promise to be observed in the present laboratory.
Abstract: We investigate the quantum dynamics and statistics of an interesting system of the double-well Bose–Einstein condensates in the presence of a coherent photo-association process occurring in one of the two wells. Through the analytical solutions of a simplified model of the atom–molecule condensate, our results show the important impact of initial state preparations on the atomic coherence, especially the different squeezing behaviour for the case of photo-association via left-well atoms tunnelling from initial right-well atomic condensate, which holds the promise to be observed in the present laboratory.
01 Oct 2003
TL;DR: In this paper, the phase dependence of quantum interference in atomic coherence system driven by microwaves is investigated and it is shown that both phase dependence interference mechanism may be destructive simultaneously and lead to spontaneous emission cancellation in different parts of the spectrum.
Abstract: Spontaneous emission in atomic system arises due to the interaction of atoms with environmental modes. Atomic coherence and quantum interference are the most important mechanisms for controlling the spontaneous emission. We show that under certain conditions complete quenching of spontaneous emission is possible. By using V type three level system driven by two fields, the phase dependence of quantum interference is investigated. The Fano type and P type interference mechanism in atomic coherence system driven by microwaves are investigated. In particular we find that both phase dependence interference mechanism may be destructive simultaneously and thus lead to spontaneous emission cancellation in different parts of the spectrum. One of the most important applications of this system is the refractive index enhancement.© (2003) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
01 Jan 2003
TL;DR: In this article, it was shown that signal and generated beams have topological charge with the same magnitude and sign, and that since they propagate in opposite directions, they should carry opposite OAM, thus demonstrating the conservation of OAM within the light modes involved in this process.
Abstract: respectively. These observed results show that signal and generated beams have topological charge with the same magnitude and sign. Therefore, since they propagate in opposite directions, they should carry opposite OAM, thus demonstrating the conservation of OAM within the light modes involved in this process. Similar results were obtained for a single charge signal beam. Our results present a first step towards the storage of a multidimensional quantum state in a long-lived atomic coherence, a subject that presents a considerable actual interest.