Showing papers on "Atomic coherence published in 2005"
TL;DR: In this paper, the authors consider the atomic dynamics and the optical response of the medium to a continuous-wave laser and show how coherently prepared media can be used to improve frequency conversion in nonlinear optical mixing experiments.
Abstract: Coherent preparation by laser light of quantum states of atoms and molecules can lead to quantum interference in the amplitudes of optical transitions. In this way the optical properties of a medium can be dramatically modified, leading to electromagnetically induced transparency and related effects, which have placed gas-phase systems at the center of recent advances in the development of media with radically new optical properties. This article reviews these advances and the new possibilities they offer for nonlinear optics and quantum information science. As a basis for the theory of electromagnetically induced transparency the authors consider the atomic dynamics and the optical response of the medium to a continuous-wave laser. They then discuss pulse propagation and the adiabatic evolution of field-coupled states and show how coherently prepared media can be used to improve frequency conversion in nonlinear optical mixing experiments. The extension of these concepts to very weak optical fields in the few-photon limit is then examined. The review concludes with a discussion of future prospects and potential new applications.
4,218 citations
TL;DR: This work considers a two-photon correlated emission laser as a source of an entangled radiation with a large number of photons in each mode, and concludes that the creation of entangled states with photon numbers up to tens of thousands seems achievable.
Abstract: We consider a two-photon correlated emission laser as a source of an entangled radiation with a large number of photons in each mode. The system consists of three-level atomic schemes inside a doubly resonant cavity. We study the dynamics of this system in the presence of cavity losses, concluding that the creation of entangled states with photon numbers up to tens of thousands seems achievable.
195 citations
TL;DR: A new experimental approach to probabilistic atom-photon (signal) entanglement is described and Polarization states of both the signal and the idler are recorded and are found to be in violation of the Bell inequality.
Abstract: We describe a new experimental approach to probabilistic atom-photon (signal) entanglement. Two qubit states are encoded as orthogonal collective spin excitations of an unpolarized atomic ensemble. After a programmable delay, the atomic excitation is converted into a photon (idler). Polarization states of both the signal and the idler are recorded and are found to be in violation of the Bell inequality. Atomic coherence times exceeding several microseconds are achieved by switching off all the trapping fields--including the quadrupole magnetic field of the magneto-optical trap--and zeroing out the residual ambient magnetic field.
176 citations
TL;DR: In this paper, the dispersion and absorption spectra of a weak probe in a three-level atomic system with closely ground sublevels driven by a strong field and damped by a broadband squeezed vacuum were analyzed.
Abstract: We study the dispersion and absorption spectra of a weak probe in a $\ensuremath{\Lambda}$-type three-level atomic system with closely ground sublevels driven by a strong field and damped by a broadband squeezed vacuum. We analyze the interplay between the spontaneous generated coherence and the squeezed field on the susceptibility of the atomic system. We find that by varying the intensity of the squeezed field the group velocity of a weak pulse can change from subluminal to superluminal. In addition we exploit the fact that the properties of the atomic medium can be dramatically modified by controlling the relative phase between the driving field and the squeezed field, allowing us to manipulate the group velocity at which light propagates. The physical origin of this phenomenon corresponds to a transfer of the atomic coherence from electromagnetically induced transparency to electromagnetically induced absorption. Besides, this phenomenon is achieved under nearly transparency conditions and with negligible distortion of the propagation pulse.
38 citations
TL;DR: In this paper, the authors investigate the coherent driving of atomic systems by complex Hyperbolic Secant (CHS) pulses in optical domain and demonstrate efficient adiabatic transfer over a few hundreds of kHz-wide spectral interval within the inhomogeneous linewidth.
Abstract: We investigate the coherent driving of atomic systems by Complex Hyperbolic Secant (CHS) pulses in optical domain. First, with the help of a Rapid Adiabatic Passage approach we get physical insight into the process. We discuss the limiting factors on spectral selectivity and transfer efficiency, such as finite coherence lifetime and excitation finite duration. Then, with a highly-stabilized cw laser and fast electronic equipment, we experimentally explore the CHS process at μs-timescale in a Tm3+:YAG crystal. We demonstrate efficient adiabatic transfer over a few hundreds of kHz-wide spectral interval within the inhomogeneous linewidth. We calculate and detect the Free Induction Decay signal as the signature of the atomic coherences during the process.
34 citations
TL;DR: In this article, the effect of diffusion of Rb atoms on electromagnetically induced transparency (EIT) in a buffer gas vapour cell was investigated, and it was shown that diffusion of atomic coherence in and out of the laser beam plays a crucial role in determining the EIT resonance lineshape and the stored light lifetime.
Abstract: We study experimentally the effect of diffusion of Rb atoms on electromagnetically induced transparency (EIT) in a buffer gas vapour cell. In particular, we find that diffusion of atomic coherence in and out of the laser beam plays a crucial role in determining the EIT resonance lineshape and the stored light lifetime.
32 citations
TL;DR: In this paper, the authors used a 1 --> 2 transition as an analytically tractable model to analyze magneto-optical resonances of both electromagnetically induced absorption (EIA) and electromagnetic induced transparency (EIT) types in the Hanle configuration.
Abstract: Using a 1 --> 2 transition as an analytically tractable model, we discuss in detail magneto-optical resonances of both electromagnetically induced absorption (EIA) and electromagnetically induced transparency (EIT) types in the Hanle configuration. The analysis is made for an arbitrary rate of depolarizing collisions in the excited state and an arbitrary elliptical field polarization. The obtained results clearly show that the main reason for the EIA subnatural resonance is the spontaneous transfer of anisotropy from the excited level to the ground level. In the EIA case we predict the negative structures in the absorption resonance at large field detuning. The role of the finite atom-light interaction time is briefly discussed. In addition we study nontrivial peculiarities of the resonance line shape related to the velocity spread in a gas.
32 citations
TL;DR: Coherent molecular optics is performed using two-photon Bragg scattering to observe the quadratic spatial dependence of the phase of an expanding molecular cloud and atoms initially prepared in two momentum states were observed to cross pair, forming molecules in a third momentum state.
Abstract: Coherent molecular optics is performed using two-photon Bragg scattering. Molecules were produced by sweeping an atomic Bose-Einstein condensate through a Feshbach resonance. The spectral width of the molecular Bragg resonance corresponded to an instantaneous temperature of 20 nK, indicating that atomic coherence was transferred directly to the molecules. An autocorrelating interference technique was used to observe the quadratic spatial dependence of the phase of an expanding molecular cloud. Finally, atoms initially prepared in two momentum states were observed to cross pair with one another, forming molecules in a third momentum state. This process is analogous to sum-frequency generation in optics.
29 citations
TL;DR: In this article, an M-type five-level atomic model is proposed to achieve a large index of refraction with vanishing absorption, and a saturation limit for the group velocity is also presented.
Abstract: An M-type five-level atomic model is proposed to achieve a large index of refraction with vanishing absorption. We present a novel model, to our knowledge, in theoretical analysis, in which an incoherent pumping rate is adopted to simplify the M-type five-level system to be an equivalent four-level system. The theoretical and experimental results show that, by adjustment of the intensity of the incoherent pump, lower group velocity (than that obtained in a conventional Lambda-type three-level electromagnetically induced transparency system) is obtained in cesium atomic vapor. Moreover, a saturation limit for the group velocity is also presented. The experimental results show good agreement with the theoretical analysis.
27 citations
TL;DR: In this paper, it was shown that if the excited states are driven by a microwave field, the resulting atomic coherence can lead to entanglement between the thermal fields, no matter how high the temperature of the fields.
Abstract: We show how atomic coherence can lead to entanglement between two thermal fields at a temperature $T$. We first show that the passage of a three-level atom in $V$ configuration without coherence cannot create entanglement. However, if the excited states are driven by a microwave field, the resulting atomic coherence can lead to entanglement between the thermal fields. We show that, no matter how high the temperature of the fields is, the thermal fields can always be entangled in the presence of atomic coherence.
23 citations
TL;DR: In this article, a measure of coherence in multiple light scattering is defined as the degree of contrast of the coherent backscattering enhancement from the vapour in ultracold atomic 85Rb.
Abstract: We report experimental observations of polarization-dependent coherence loss occurring in strong-field multiple scattering of light in ultracold atomic 85Rb. A measure of coherence in multiple light scattering is the degree of contrast of the coherent backscattering enhancement from the vapour. For resonance saturation parameters up to 9, we see light-polarization-dependent modification of the backscattering enhancement, suggesting that inelastic atomic light scattering and dynamic atomic magnetization may play important roles in the multiple scattering process for 85Rb.
TL;DR: In this paper, the ground-state hyperfine splitting of 85Rb atoms trapped in far-off-resonance optical traps is studied and the existence of a spatially dependent shift in the energy levels is shown to induce an inherent dephasing effect, which causes a broadening of the spectroscopic line and hence an inhomogeneous loss of atomic coherence at a much faster rate than the homogeneous one caused by spontaneous photon scattering.
Abstract: We perform spectroscopy on the ground-state hyperfine splitting of 85Rb atoms trapped in far-off-resonance optical traps. The existence of a spatially dependent shift in the energy levels is shown to induce an inherent dephasing effect, which causes a broadening of the spectroscopic line and hence an inhomogeneous loss of atomic coherence at a much faster rate than the homogeneous one caused by spontaneous photon scattering. We present here a number of approaches for reducing this inhomogeneous broadening, based on trap geometry, additional laser fields, and novel microwave pulse sequences. We then show how hyperfine spectroscopy can be used to study the quantum dynamics of optically trapped atoms.
TL;DR: In this paper, a three-level atomic system in V-configuration with parallel transition dipole moments exhibiting spontaneously generated coherence due to quantum interference of decaying channels is considered for the purpose of storing light pulses.
Abstract: A three-level atomic system in V-configuration (interacting with a single mode laser field) with parallel transition dipole moments exhibiting spontaneously generated coherence due to quantum interference of decaying channels is considered here for the purpose of storing light pulses. This system is equivalent to (with some restrictions) another three-level system in which ground state is coupled with one of the upper states but the upper states are coupled through a DC field and hence can be used to store electromagnetic pulse using the concept of dark-state-polariton.
TL;DR: This work theoretically predict and experimentally demonstrate chaotic behaviors in a system comprising of three-level atoms inside an optical ring cavity driven to chaos through period-doubling route by reducing the frequency detuning of the coupling laser beam.
Abstract: We theoretically predict and experimentally demonstrate chaotic behaviors in a system comprising of three-level atoms inside an optical ring cavity. This electromagnetically induced transparency (EIT) system is driven to chaos through period-doubling route by reducing the frequency detuning of the coupling laser beam. The chaos occurs in a different parametric regime as previously predicted and is believed to be caused by the enhanced dispersion and nonlinearity due to induced atomic coherence in such EIT system.
TL;DR: In this article, nonlinear properties of electromagnetically induced transparency with respect to a weak probe light are studied, and the influence of the probe dependence on the performance of the EIT-based optical delay lines and magnetometers is theoretically studied.
Abstract: Nonlinear properties of electromagnetically induced transparency (EIT) with respect to a weak probe light are studied. We observe EIT in a rubidium vapor, measure the slow light group velocity and the EIT resonance width, and find that those parameters show a strong dependence on the probe power. We theoretically study the influence of the EIT probe dependence on the performance of the EIT-based optical delay lines and magnetometers.
TL;DR: In this article, a simple analytical solution for the propagation of a weak Gaussian pulse in a dense absorptive medium with electromagnetically induced transparency is found, which is applied to the analysis of three regimes: (1) and (2) the pulse spectrum is narrower than the transparency window.
Abstract: A simple analytical solution for the propagation of a weak Gaussian pulse in a dense absorptive medium with electromagnetically induced transparency is found. This solution is applied to the analysis of three regimes: (1) and (2) the pulse spectrum is narrower than the transparency window [which is narrow (1) or wide (2) with respect to the width of the absorption line] and (3) the pulse spectrum is broader than the transparency window. It is shown that the pulse maintains its area in all three regimes and maintains its Gaussian shape but narrows in spectrum in regime 1. In regime 2, the pulse begins to distort after a certain distance. In regime 3, the pulse is split into two parts. One part is an adiabatic part with a spectrum defined by the effective width of the transparency window for a thick medium and the other is an oscillating nonadiabatic part of short duration. The adiabatic part propagates slowly and the nonadiabatic part propagates with a velocity close to the speed of light. Thus in regime 3, the medium acts as a time-frequency filter, separating the narrow and wide spectrum components of the pulse in time at the output of the absorber.
TL;DR: In this article, a fully quantum mechanical solution of the dissipative motion of an atomic centre-of-mass strongly coupled to a dynamically varying cavity field mode is presented, and the coherence properties of the atomic wave packet and its entanglement to the cavity field are calculated.
Abstract: A fully quantum mechanical solution of the dissipative motion of an atomic centre-of-mass strongly coupled to a dynamically varying cavity field mode is presented. Beyond the statistical properties, such as the temperature and localization of the atom, the coherence properties of the atomic wave packet and its entanglement to the cavity field are calculated. The latter is the source of a nonclassical photon statistics expressed in terms of the Mandel Q parameter. The trapping time of an atom initially localized in a potential well is found to significantly deviate from the semiclassically expected results, which we attribute to the graininess of the photon field.
TL;DR: In this paper, a scheme that performs a SWAP gate between two photons at different wavelengths with near 100% fidelity was described. But the SWAP was performed using electromagnetically induced transparency.
Abstract: We describe a scheme that performs a SWAP gate between two photons at different wavelengths with near 100% fidelity. The essential idea is the preparation of a near-maximal atomic coherence using electromagnetically induced transparency.
TL;DR: In this paper, a mean field theory for Raman superradiance with recoil is presented, where the typical SR signatures are recovered, such as quadratic dependence of the intensity on the number of atoms and inverse proportionality of the time scale to the number, and a comparison with recent experiments and theories on Rayleigh SR and collective atomic recoil lasing are included.
Abstract: A mean field theory for Raman superradiance (SR) with recoil is presented, where the typical SR signatures are recovered, such as quadratic dependence of the intensity on the number of atoms and inverse proportionality of the time scale to the number of atoms. A comparison with recent experiments and theories on Rayleigh SR and collective atomic recoil lasing (CARL) are included. The role of recoil is shown to be in the decay of atomic coherence and breaking of the symmetry of the SR end-fire modes.
TL;DR: This technique allows us to design not only the quantum non-demolition coupling, but also beam splitter-like and two-mode squeezer-like interactions between light and collective atomic spin.
Abstract: Present schemes involving the quantum nondemolition interaction between atomic samples and off-resonant light pulses allow us to store quantum information corresponding to a single harmonic oscillator (mode) in one multiatomic system. We discuss the possibility of involving several coherences of each atom so that the atomic sample can store information contained in several quantum modes. This is achieved by the coupling of different magnetic sublevels of the relevant hyperfine level by additional Raman pulses. This technique allows us to design not only the quantum nondemolition coupling, but also beam splitterlike and two-mode squeezerlike interactions between light and collective atomic spin.
TL;DR: In this paper, a Doppler-broadened He-Ne mixture was used as active medium to obtain up-conversion lasing without inversion in the visible range.
Abstract: A scheme for obtaining up-conversion lasing without inversion in the visible range is proposed using a Doppler-broadened He-Ne mixture as active medium. We consider a cascade scheme (2s2↔2p2↔1s3) with a frequency up-conversion ratio of 1.91. The upper transition is inverted and driven by an external field and lasing without inversion occurs at 616.4 nm provided that the collisional decay rates of the 1s3 and 1s5 levels overcome a certain threshold.
TL;DR: In this paper, a scheme of optical polarization modulation of a linearly polarized infrared probe field is studied in a degenerate four-level Yb atomic system, where the authors have observed an anomalous transmission spectra of two circular polarization components of the probe field exhibiting an enhanced two-photon absorption and a threephoton gain with comparable magnitude leading to the lossless transmission and enhanced circular dichroism.
Abstract: A scheme of optical polarization modulation of a linearly polarized infrared probe field is studied in a degenerate four-level Yb atomic system. We have observed an anomalous transmission spectra of two circular polarization components of the probe field exhibiting an enhanced two-photon absorption and a three-photon gain with comparable magnitude, leading to the lossless transmission and enhanced circular dichroism. We carried out a proof-of-principle experiment of fast optical polarization modulation in such a system by modulating the polarization state of the coupling field. The observed enhanced two-photon absorption and three-photon gain of the probe field are due to the result of competing atomic coherence effects.
TL;DR: In this article, the steady state behavior of a mesoscopic system of coherently injected two-level Rydberg atoms with a coherently driven single-mode cavity is investigated in both resonant and non-resonant regimes.
Abstract: The steady state behaviour describing the interaction of a mesoscopic system of coherently injected two-level Rydberg atoms with a coherently driven single-mode cavity is investigated in both resonant and non-resonant regimes. Multiple-switching effects between the output field states are predicted with the atomic coherent excitation (θ) and relative coherent phase parameter (Φr) of the atomic coherent state . The relation between the transmitted field (x) and the atomic cooperation parameter (C) shows multistable behaviour for some values of the polar and azimuthal angles (θ,). The transverse field feature in the form of a Gaussian beam profile tends to degrade the multistable structure in the (C–x) and the input–output field (x–Y) relations. Micromaser action is analysed for the system with atomic coherence within and without the plane wave approximation.
TL;DR: In this paper, the phase-dependent squeezing of resonance fluorescence emitted from a coherently excited three-level atom with a ladder configuration of energy levels was investigated and the optimal phase of quadrature of fluorescent light, intensity and detuning of the driving fields and the decay rate of the controlling transition were calculated.
TL;DR: In this paper, spontaneous coherence grating transfer between different pairs of Zeeman sublevels belonging to different cesium hyperfine states was observed, where coherent Bragg diffraction was employed as a signature of the transfer mechanism; this spectrum showed a subnatural linewidth.
Abstract: We report on the direct observation of spontaneous coherence grating transfer between different pairs of Zeeman sublevels belonging to different cesium hyperfine states. Coherent Bragg diffraction is employed as a signature of the transfer mechanism; this spectrum shows a subnatural linewidth. Theoretically we model the observed effect using a tensorial density matrix formalism to describe the light interaction with a pair of degenerate two-level systems coupled by spontaneous emission. The possibility of transferring a short-lived atomic coherence into a long-lived one might be of considerable importance for the growing field of quantum-information processing.
TL;DR: In this paper, the authors studied the polarization effects and coupling intensity effects of electromagnetically induced transparency (EIT) in the 5S2/5P2-/5D2/ ladder system of Rb.
Abstract: We have studied the polarization effects and the coupling intensity effects of electromagnetically induced transparency(EIT) in the 5S2-/5P2-/5D2/ ladder system of Rb. We obtained the EIT spectrum with the hyperfine structure of 5D2/ transitions and the minimal width of the measured EIT spectrum was 6.5 MHz. We observed the change of the relative magnitudes of the hyperfine structure of EIT according to not only the polarizations of lasers but also the intensity of the coupling laser. The cause of the coupling intensity effects is that the EIT signal nonlinearly increases to the coupling intensity.
TL;DR: In this paper, the authors derived an expression of the interaction between a quantum cavity field and an ultracold Λ-type three-level atom in which two upper levels are coupled by a coherent driving field.
Abstract: We derive an expression of the interaction between a quantum cavity field and an ultracold Λ-type three-level atom in which two upper levels are coupled by a coherent driving field. The effects of the driving-induced atomic coherence on the atomic emission probability are investigated. It is found that, due to the driving-induced atomic coherence, there are two transition channels for the atom interacting with the cavity field. Between the two transition channels, there is a quantum interference, which is a destructive interference. This destructive quantum interference suppresses the emission of the atom. The atomic emission probability decreases with the increasing driving field.
TL;DR: In this article, an analytical calculation to determine the atomic injection time effects on lasing without inversion (LWI) in a three level lambda system with its ground state driven by an arbitrarily strong classical microwave field is presented.
Abstract: We present an analytical calculation to determine the atomic injection time effects on lasing without inversion (LWI) in a three level lambda system with its ground state driven by an arbitrarily strong classical microwave field. We systematically take into account subtle effects associated with the injection times. We derive an expression for the optical coherences and show that one gets amplification of the field without population inversion which is governed by a temporal phase, in addition to the initial (random) phases of the ground state coherence.
TL;DR: In this article, the authors studied the nonlinear processes occurring during the propagation of light pulses in optical fibers doped with atoms of rare-earth elements under conditions of atomic coherence and interference.
Abstract: Results of study of nonlinear processes occurring during the propagation of light pulses in optical fibers doped with atoms of rare-earth elements under conditions of atomic coherence and interference are presented. For a three-level Λ scheme of interaction, the linear (χ(1)) and nonlinear (χ(3)) susceptibilities of such a medium are calculated. It is shown that the coefficients of Kerr nonlinearity and nonlinear absorption can reach extremely large values and can be negative. The competition between linear and nonlinear processes in the Λ scheme allows one to obtain compensation regimes when the coefficients of dispersion or absorption of the optical fiber material vanish. The efficient control of the optical properties of such a system over wide limits proves to be possible owing to variations in the parameters of light pulses at the input of the medium. The necessary conditions for realizing regimes with “slow” light, as well as for self-compression of a probing pulse on ultimately small spatial scales in a doped optical fiber, were obtained.
TL;DR: In this paper, a two-photon micromaser with atoms injected in the superposition state of the upper and intermediate levels is simulated by the Monte Carlo wavefunction approach and analyzed as a function of the atomic transit time.
Abstract: We investigate the quantum dynamics of a two-photon micromaser pumped by atoms injected in the superposition state of the upper and intermediate levels. We simulate a master equation governing the system by the Monte Carlo wavefunction approach and analyse the steady-state behaviour as a function of the atomic transit time. The atomic coherence can effectively enhance the intensity and sub-Poissonian of the cavity field as compared with the atomic mixture. It is also discovered that the phase of the cavity field can be shifted by adjusting the detuning between the atom and field. This result shows that it is possible to manipulate the phase of the cavity field by detuning, due to atomic coherence.