Showing papers on "Atomic coherence published in 2007"
TL;DR: The simultaneously opened dual electromagnetically induced transparency windows in this four-level atomic system allow observation of these two nonlinear optical processes at the same time, which enables detailed studies of the interplay between the FWM and SWM processes.
Abstract: Highly efficient four-wave mixing (FWM) and six-wave mixing (SWM) processes can coexist in a four-level Y-type atomic system due to atomic coherence The simultaneously opened dual electromagnetically induced transparency windows in this four-level atomic system allow observation of these two nonlinear optical processes at the same time, which enables detailed studies of the interplay between the FWM and SWM processes Three-photon and five-photon destructive interferences are also observed
267 citations
TL;DR: In this article, the carrier-envelope phase (CEP) of few-cycle laser pulses has profound effects on the bound-state atomic coherence even in the weak-field regime where both tunneling and multiphoton ionization hardly take place.
Abstract: It is shown that the carrier-envelope phase (CEP) of few-cycle laser pulses has profound effects on the bound-state atomic coherence even in the weak-field regime where both tunneling and multiphoton ionization hardly take place. The atomic coherence thus produced is shown to be able to be mapped onto the CEP-dependent signal of quantum beats (and other quantum-interference phenomena) and hence might be used to extract information about and ultimately to measure the carrier-envelope phase.
106 citations
TL;DR: In this article, nonlinear optical phenomena from collective motion of ultracold atoms within a strong-coupling cavity are reported. The nonlinearity arises from probe-induced atom displacement.
Abstract: We report on nonlinear optical phenomena from collective motion of ultracold atoms within a strong-coupling cavity. The nonlinearity arises from probe-induced atom displacement. Longevity of motional coherence allows nonlinearity at extremely low cavity photon numbers.
65 citations
TL;DR: In this article, the authors considered a three-level cascade laser with a subthreshold non-degenerate parametric oscillator coupled to a vacuum reservoir and analyzed the squeezing and entanglement properties of the two-mode light produced by this quantum optical system inside and outside the cavity.
Abstract: We consider a nondegenerate three-level cascade laser with a subthreshold nondegenerate parametric oscillator coupled to a vacuum reservoir. Applying the pertinent master equation, we analyze the squeezing and entanglement properties of the two-mode light produced by this quantum optical system inside and outside the cavity. We also determine the normalized second-order correlation function for the two-mode light as well as for individual mode. We find that the light generated by this system is in a two-mode squeezed state and the state of the system is strongly entangled at steady state. Moreover, the presence of the parametric oscillator leads to an increase in the degree of squeezing and entanglement. We also find that the intermode correlation decreases as the injected atomic coherence decreases in the system.
45 citations
TL;DR: Generation of four-wave mixing enhanced by electromagnetically induced transparency and optical pumping in a ladder-type atomic system and interference between these two nonlinear wave-mixing signals is experimentally demonstrated.
Abstract: We report generation of four-wave mixing enhanced by electromagnetically induced transparency and optical pumping in a ladder-type atomic system. When two pumping laser beams are used to form a conjugate small-angle static grating, both four-wave and six-wave mixing processes are shown to exist at the same time. Interference between these two nonlinear wave-mixing signals is experimentally demonstrated.
33 citations
TL;DR: In this article, two four-wave mixing (FWM) processes can coexist in a four-level Y-type atomic system with carefully arranged coupling laser beams, which can be tuned to overlap or separate by various frequency detunings.
Abstract: Two four-wave-mixing (FWM) processes can coexist in a four-level Y-type atomic system with carefully arranged coupling laser beams. The generated two FWM signal beams fall into two simultaneously opened dual electromagnetically induced transparency (EIT) windows, which can be tuned to overlap or separate by various frequency detunings. The authors report our experimental observation of competing FWM processes, especially mutual suppression of the two FWM signals when the two EIT windows merge in frequency. Controlling FWM processes can have important applications in wavelength conversion for optical communication.
30 citations
TL;DR: In this article, the authors considered the coexisting dressed four-wave mixing (FWM) and six wave mixing (SWM) in an open four-level inverted Y configuration and reported an experimental observation of optical pumping assisted FWM and electromagnetically induced transparency (EIT)-assisted SWM.
Abstract: The authors have considered the coexisting dressed four-wave mixing (FWM) and six-wave mixing (SWM) in an open four-level inverted Y configuration. The authors also report an experimental observation of optical pumping-assisted FWM and electromagnetically induced transparency (EIT)-assisted SWM. The efficient SWM can be selected by EIT window and controlled by the coupling as well as dressed field detuning and power. Due to EIT and optical pumping assistance, the enhanced SWM signal is more than ten times lager than the coexisting FWM signal.
27 citations
TL;DR: In this article, an experimental study of atomic coherence and interference in a three-level system of cold Rb atoms driven by multicolor coupling and probe fields is presented.
Abstract: We report an experimental study of atomic coherence and interference in a three-level $\ensuremath{\Lambda}$ system of cold Rb atoms driven by multicolor coupling and probe fields. The multicolor coupling and probe fields open multiple channels for a two-photon Raman process. Interference between the open channels leads to rich spectral features in the $\ensuremath{\Lambda}$ system and can be controlled by the phase of the probe field. The constructive-interference-induced transparency or the destructive-interference-induced absorption with a subnatural linewidth can be selectively created near the atomic resonance.
18 citations
TL;DR: Eisaman et al. as mentioned in this paper used a room-temperature ensemble of 87Rb atoms to generate a single photon using electromagnetically induced transparency (EIT).
Abstract: We review recent experiments [M. D. Eisaman et al., Nature438 (2005) 837] demonstrating the generation of narrow-bandwidth single photons using a room-temperature ensemble of 87Rb atoms. Our method involves creation of an atomic coherence via Raman scattering and projective measurement, followed by the coherent transfer of this atomic coherence onto a single photon using electromagnetically induced transparency (EIT). The single photons generated using this method are shown to have many properties necessary for quantum information protocols, such as narrow bandwidths, directional emission, and controllable pulse shapes. The narrow bandwidths of these single photons (~MHz), resulting from their matching to the EIT resonance (~MHz), allow them to be stored in narrow-bandwidth quantum memories. We demonstrate this by using dynamic EIT to store and retrieve the single photons in a second ensemble for storage times up to a few microseconds. We also describe recent improvements to the single-photon fidelity compared to the work by M. D. Eisaman in Nature438 (2005) 837. These techniques may prove useful in quantum information applications such as quantum repeaters, linear-optics quantum computation, and daytime free-space quantum communication.
16 citations
TL;DR: Using room-temperature 87Rb atoms, a quantum destructive interference between two one-photon excitation pathways in an inelastic two-wave mixing scheme that corresponds to the "strong-storage and weak-retrieval" of an optical field is demonstrated.
Abstract: Using room-temperature Rb-87 atoms we demonstrate a quantum destructive interference between two one-photon excitation pathways in an inelastic two-wave mixing scheme that corresponds to the "strong-storage and weak-retrieval" of an optical field. This destructive interference is fundamentally different from the usual electromagnetically induced transparency because it is critically dependent on the generation and propagation of a wave-mixing field. We also show that contrary to the common belief, the maximum atomic coherence in general does not lead to the maximum mixing-wave conversion efficiency.
15 citations
TL;DR: In this paper, two identical two-level atoms interacting with a single-mode thermal field through two-photon processes were studied, and it was shown that the entanglement is greatly enhanced due to the initial atomic coherence.
Abstract: Considering two identical two-level atoms interacting with a single-mode thermal field through two-photon processes, this paper studies the atomic coherence control on the entanglement between two two-level atoms, and finds that the entanglement is greatly enhanced due to the initial atomic coherence. The results show that the entanglement can be manipulated by changing the initial parameters of the system, such as the superposition coefficients and the relative phases of the initial atomic coherent state and the mean photon number of the cavity field.
TL;DR: The preparation and probing of the coherence between the hyperfine ground states |S(1/2),F=1> and |5S( 1/2,F=2> of the Rb87 isotope is demonstrated and the effects of various coherence control techniques are investigated.
Abstract: We demonstrate the preparation and probing of the coherence between the hyperfine ground states |S1/2,F=1> and |5S1/2,F=2> of the Rb87 isotope. The effects of various coherence control techniques, i.e., fractional stimulated Raman adiabatic passage and coherent population return, on the coherence are investigated. These techniques are implemented using nearly degenerate pump and Stokes lasers at 795 nm (Rb D1 transition), which couple the two hyperfine ground states via the excited state |5P1/2,F=1> through a resonant two-photon process in which a coherent superposition of the two hyperfine ground states is established. The medium is probed by an additional weak laser, which generates a four-wave mixing signal proportional to the ground state coherence and allows us to monitor its evolution in time. The experimental data are compared with numerical simulations.
Dissertation•
09 Feb 2007
TL;DR: In this paper, the authors report on three different experiments: i) the determination of the two and three-body ionizing rate constants of He*, ii) a, the He* scattering length; iii) the measure of the intensity correlation function of a falling He* cloud.
Abstract: In 2001 metastable Helium (He*) attained Bose-Einstein condensation (BEC). The metastable state has a lifetime of 9000 sec and an internal energy of 20 eV. This energy can be used to detect individual atoms using a micro-channel plate. The extremely good time response and high gain of this detector makes it possible to carry out a density correlation measurement (HBT) with massive particles similar to the pioneering experiment of R. Hanbury Brown and R. Twiss in optics. In addition, inelastic collisions between He* atoms produce a small but detectable flux of ions proportional to the cloud's density. This allows one to follow the evolution of the cloud's density toward BEC, passing through the phase transition, in real time and in a non invasive way. In this dissertation we report on three different experiments: i) the determination of the two- and three-body ionizing rate constants of He*; ii) the determination of a, the He* scattering length; iii) the measure of the intensity correlation function of a falling He* cloud. It has been shown lately that our measure of a was affected by a large systematic error and we propose a possible explanation. We describe methods to determine the temperature and fugacity of a thermal cloud. Finally a major portion of the thesis is devoted to the derivation of an analytical expression for the intensity correlation function of the atomic flux. This theoretical analysis has derived typical values for the transverse and longitudinal atomic coherence length that confirmed the possibility of performing a HBT experiment with our apparatus.
TL;DR: In this paper, the propagation of an arbitrary polarized few-cycle ultrashort laser pulse in a degenerate three-level medium was investigated by using an iterative predictor-corrector finite-difference time-domain method.
Abstract: The propagation of an arbitrary polarized few-cycle ultrashort laser pulse in a degenerate three-level medium is investigated by using an iterative predictor-corrector finite-difference time-domain method. It is found that the polarization evolution of the ultrashort laser pulse is dependent not only on the initial atomic coherence of the medium but also on the polarization condition of the incident laser pulse. When the initial effective area is equal to 2 pi, complete linear-to-circular and circular-to-linear polarization conversion of few-cycle ultrashort laser pulses can be achieved due to the quantum interference effects between the two different transition paths.
TL;DR: In this article, the dispersion slope of the EIT signal at the resonance frequency of the probe beam was calculated by taking the 2 derivative of the measured EIT signals, and it was shown that there existed an optimum temperature at which the temperature had a maximum value, considering the Doppler effect and the atomic coherence relaxation due to atomic collisions.
Abstract: The temperature dependence of electromagnetically induced transparency (EIT) in a Cs atomic vapor cell was investigated A probe laser beam frequency was scanned around the resonance frequency of the transition line 6S1/2, F = 3 → 6P3/2, F′ = 4 while the coupling beam frequency was locked to the transition line 6S1/2, F = 4→ 6P3/2, F′ = 4 In order to analyze the temperature dependence of the EIT signal quantitatively, we calculated the dispersion slope of the EIT signal at the resonance frequency of the probe beam by taking the 2 derivative of the measured EIT signal We found that there existed an optimum temperature at which the dispersion slope had a maximum value This temperature dependence of the EIT signal was well explained by the calculated results considering the Doppler effect and the atomic coherence relaxation due to atomic collisions
TL;DR: In this article, the absorption profile of a four-level ladder atomic system interacting with three driving fields is studied perturbatively and analytical results are presented, where the driving field strengths are treated up to all orders.
Abstract: The absorption profile of a four-level ladder atomic system interacting with three driving fields is studied perturbatively and analytical results are presented. Numerical results where the driving field strengths are treated up to all orders are presented. The absorption features are studied in two regimes—(i) the weak middle transition coupling, i.e. Ω2 Ω1,3 and (ii) the strong middle transition coupling Ω2 Ω1,3. In case (i), it is shown that the ground-state absorption and the saturation characteristics of the population of level |2 reveal deviation due to the presence of upper level couplings. In particular, the saturation curve for the population of level |2 shows a dip for Ω1 = Ω3. While the populations of levels |3 and |4 show a maxima when this resonance condition is satisfied. Thus the resonance condition provides a criterion for maximally populating the upper levels. A second-order perturbation calculation reveals the nature of these minima (maxima). In the second case, I report two important features: (a) filtering of the Aulter–Townes doublet in the three-peak absorption profile of the ground state, which is achieved by detuning only the uppermost coupling field and (b) control of line-width by controlling the strength of the upper coupling fields. This filtering technique coupled with the control of linewidth could prove to be very useful for high resolution studies.
TL;DR: In this paper, the control role of the relative phase between the probe and driving fields on the gain and dispersion in an open three-level ladder atomic system with incoherent pumping and spontaneously generated coherence is investigated.
TL;DR: In this paper, the authors considered the generation of continuous variable entanglement via atomic coherence in a two-mode three-level cascade atomic system with two photons of a strong external pump field.
Abstract: The generation of continuous variable entanglement via atomic coherence in a two-mode three-level cascade atomic system is discussed according to the entanglement criterion proposed by Duan et al. [Phys. Rev. Lett. 84, 2722 (2000)]. Atomic coherence between the top and bottom levels is induced with two photons of a strong external pump field. It shows that entanglement for the two-mode field in the cavity can be generated under certain conditions. Moreover, by means of the input-output theory, we show that the two-mode entanglement could also be approached at the output.
TL;DR: In this paper, the authors developed a theory of two-mode entanglement amplifier in a cascade three-level atomic system and showed that the creation of strongly entangled states with very large photon numbers seems achievable.
TL;DR: In this article, the photonic bands of an atomic Bose-Einstein condensate with a triangular vortex lattice were investigated, and the frequency-dependent dielectric function was used in the calculations, resulting in photonic band gap widths of a few megahertz.
Abstract: Received 26 March 2007; published 27 June 2007We investigate the photonic bands of an atomic Bose-Einstein condensate with a triangular vortex lattice.Index contrast between the vortex cores and the bulk of the condensate is achieved through the enhancementof the index via atomic coherence. The frequency-dependent dielectric function is used in the calculations ofthe bands, resulting in photonic band gap widths of a few megahertz.DOI: 10.1103/PhysRevA.75.063627 PACS number s : 03.75.Lm, 42.50.Gy, 42.70.Qs, 74.25.Qt
TL;DR: In this article, two-photon resonant non-degenerate four-wave mixing (NFWM) with the addition of a coupling field in Ba atomic vapour has been studied.
Abstract: Two-photon resonant nondegenerate four-wave mixing (NFWM) with the addition of a coupling field in Ba atomic vapour has been studied. We find that coherence of the atomic level transitions leads to suppression of the NFWM signal, giving rise to a dip with a linewidth that is linearly proportional to the intensity of the coupling field.
TL;DR: In this paper, a slow-light beam-plitter using the rapid transport of coherence in a wall-coated atomic vapor cell under electromagnetically-induced transparency is presented.
Abstract: A slow-light beamsplitter using the rapid transport of coherence in a wall-coated atomic vapor cell under electromagnetically-induced-transparency is presented. Such a beamsplitter may improve quantum repeater performance and be useful in quantum and classical optics.
TL;DR: In this paper, a three-level Λ-type Rb87 atomic system was used to store optical pulses and selectively release them at one of the two different wavelengths by turning on the retrieve control pulse at 794.9842 or 701.9698nm.
Abstract: The authors report an experiment in which optical pulses are effectively stored via maximal atomic coherence in a three-level Λ-type Rb87 atomic system, and then selectively released at one of the two different wavelengths by turning on the retrieve control pulse at 794.9842 or 794.9698nm. The storage time up to 360ns was demonstrated.
TL;DR: The atomic coherence and the population transfer among Rb hyperfine atomic levels by the fractional stimulated Raman adiabatic passage (F-STIRAP) in a L-type configuration is controlled, and the theoretical predictions are verified.
Abstract: We control the atomic coherence and the population transfer among Rb hyperfine atomic levels by the fractional stimulated Raman adiabatic passage (F-STIRAP) in a L-type configuration, and verify the theoretical predictions. Applying this technique, we are able to prepare the atoms with maximal coherence to enhance coherent anti-Stokes Raman scattering (CARS) signal. In our experiment by scanning the frequency of one laser from 794.9839 nm to 794.9844 nm with the 794.9698 nm laser frequency fixed to generate a maximum of the CARS signal we are able to obtain the energy level diagram of the sample.
TL;DR: In this article, the authors investigated the dressed effects of non-degenerate four-wave mixing (NDFWM) and demonstrated a phase-sensitive method of studying the fifth-order nonlinear susceptibility due to atomic coherence in RN-type four-level system.
Abstract: We have investigated the dressed effects of non-degenerate four-wave mixing (NDFWM) and demonstrated a phase-sensitive method of studying the fifth-order nonlinear susceptibility due to atomic coherence in RN-type four-level system. In the presence of a strong coupling field, NDFWM spectrum exhibits Autler–Townes splitting, accompanied by either suppression or enhancement of the NDFWM signal, which is directly related to the competition between the absorption and dispersion contributions. The heterodyne-detected nonlinear absorption and dispersion of six-wave mixing signal in the RN-type system show that the hybrid radiation-matter detuning damping oscillation is in the THz range and can be controlled and modified through the colour-locked correlation of twin noisy fields.
TL;DR: In this article, the spectral line narrowing effect in a three-level atomic system where one transition is coupled by a coupling laser and the narrow feature is observed by probing the other transition with a weak laser is investigated.
Abstract: We present the spectral line narrowing effect in a Λ three-level atomic system where one transition is coupled by a coupling laser and the narrow feature is observed by probing the other transition with a weak laser. As coupling laser detuning increases the electromagnetically induced transparency resonance is observed to evolve into electromagnetically induced absorption resonance with sub-natural linewidth. The linewidth of the narrow spectral feature is studied as a function of coupling laser detuning and the atomic system parameters. The result is explained using density matrix density equation in the dressed-atom picture.
02 Mar 2007
TL;DR: In this paper, the authors studied experimentally and theoretically the Hanle EIA on the closed F g = 3 : F e = 4 D2 transition of 85 Rb. Atoms were excited by the laser light with different polarization, fr om linear to circular.
Abstract: We have studied experimentally and theoretically Hanle EIA on the closed F g = 3 : F e = 4 D2 transition of 85 Rb. Atoms were excited by the laser light with different polarization, fr om linear to circular. Results of the theoretical calculations of the laser transmission, based on optical Bloch equations for density matrix elements for the same atomic system, show important effects of magnetic field transverse to the laser light . We were not able to control transverse magnetic field in the experiment but the theoretical results are still applicable to our experimental data due the presence of laboratory stray magnetic field in the vicinity of the Rb cell, occurring because of imperfect magnetic shielding. Keywords: Electromagnetically induced absorption, Coherent population trapping 1. INTRODUCTION Electromagnetically induced absorption (EIA) is characterized by an increased absorption of radiation due to atomic coherence. 1 Its origin is in the spontaneous transfer of the light induced anisotropy from excited state to a ground state Zeeman sublevels. The anisotropy can be either due to atomic coherence or population difference created among degenerate Zeeman sublevels of the excited state hyperfine level when laser lights couple atomic levels such that F
TL;DR: In this paper, the influence of incoherent optical pumping and beam profiling on slow light propagation in three-level atomic vapor was studied and it was shown that the optical pumping enhances the resulting group delay for a certain range of parameters.
Abstract: We report on a theoretical study of the influence of incoherent optical pumping and beam profiling on slow light propagation in three-level atomic vapor. The pumping reduces the residual unwanted absorption of the signal while destroying the atomic coherence and increasing the group velocity of light. We show that the pumping enhances the resulting group delay for a certain range of parameters. We also examine changing the cross section of the beam of light along the propagation direction by, e.g., focusing the beam, for the purpose of maintaining the drive intensity to effectively counter its absorption.
13 Sep 2007
TL;DR: In this article, a wave propagation along a slowly axially varying, adiabatically tapered, negative refractive index metamaterial heterostructure is proposed for slowing and stopping/storing light.
Abstract: We introduce an efficient method for slowing and stopping/storing light, which is based on wave propagation along a
slowly axially varying, adiabatically tapered, negative refractive index metamaterial heterostructure. We analytically
show that the present method can, in principle, simultaneously allow for broad bandwidth operation (since it does not
rely on group index resonances), large delay-bandwidth products (since a wave packet can be completely stopped and
buffered indefinitely) and high, almost 100%, in/out-coupling efficiencies. Moreover, by nature, the presented scheme
invokes solid-state materials and, as such, is not subject to low-temperature or atomic coherence limitations. This method
for trapping photons conceivably opens the way to a multitude of hybrid, optoelectronic devices to be used in 'quantum
information' processing, communication networks and signal processors, and may herald a new realm of combined
metamaterials and slow light research.
08 Feb 2007
TL;DR: In this paper, it was shown that dispersion due to an intra-cavity electromagnetically induced transparency or gain medium reduces the sensitivity of the cavity resonance frequency to a change in its length by a factor which is inversely proportional to the group index.
Abstract: We have shown experimentally that dispersion due to an intra-cavity electromagnetically induced
transparency or gain medium reduces the sensitivity of the cavity resonance frequency to a change in its
length by a factor which is inversely proportional to the group index. Since the group index under atomic
coherence can be made extremely large, the sensitivity of a long path length optical cavity can be reduced
significantly. This can help in constructing highly frequency-stable cavities for various potential applications
without taking additional measures for mechanical stability. The results also establish indirectly the opposite
effect of increased sensitivity that can be realized for a negative dispersion corresponding to a group index
close to a null value. These effects are discussed in the context of potential sensitivity enhancement of a
rotation sensor.