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Showing papers on "Atomic coherence published in 2011"


Journal ArticleDOI
TL;DR: In this paper, the authors describe how electromagnetically induced transparency can arise in quadratically coupled optomechanical systems and show how the fluctuation in displacement can play a role similar to atomic coherence and can lead to EIT-like effects.
Abstract: We describe how electromagnetically induced transparency can arise in quadratically coupled optomechanical systems. Due to quadratic coupling, the underlying optical process involves a two-phonon process in an optomechanical system, and this two-phonon process makes the mean displacement, which plays the role of atomic coherence in traditional electromagnetically induced transparency (EIT), zero. We show how the fluctuation in displacement can play a role similar to atomic coherence and can lead to EIT-like effects in quadratically coupled optomechanical systems. We show how such effects can be studied using the existing optomechanical systems.

116 citations


Journal ArticleDOI
TL;DR: In this article, a scheme for three-level cascade atoms to entangle two optomechanical oscillators as well as two-mode fields was proposed, and it was shown that two movable mirrors and twomode fields can be entangled even for bad cavity limits.
Abstract: We propose a scheme for three-level cascade atoms to entangle two optomechanical oscillators as well as two-mode fields. We show that two movable mirrors and two-mode fields can be entangled even for bad cavity limits. We also study entanglement of the output of two-mode fields in the frequency domain. The results show that the frequency of the mirror oscillation and the injected atomic coherence affect the output entanglement of the two-mode fields.

90 citations


Journal ArticleDOI
TL;DR: In this paper, a broad-band detector of gravitational radiation is proposed, which relies on two atom interferometers separated by a distance L. In this scheme, only one arm and one laser will be used for operating the two atoms, and atomic coherence is intrinsically stable and can be many orders of magnitude more stable than a laser.
Abstract: We present a new general design approach of a broad-band detector of gravitational radiation that relies on two atom interferometers separated by a distance L. In this scheme, only one arm and one laser will be used for operating the two atom interferometers. We consider atoms in the atom interferometers not only as perfect inertial reference sensors, but also as highly stable clocks. Atomic coherence is intrinsically stable and can be many orders of magnitude more stable than a laser. The unique one-laser configuration allows us to then apply time-delay interferometry to the responses of the two atom interferometers, thereby canceling the laser phase fluctuations while preserving the gravitational wave signal in the resulting data set. Our approach appears very promising. We plan to investigate further its practicality and detailed sensitivity analysis.

71 citations


Journal ArticleDOI
TL;DR: In this article, the authors report experimental storage and retrieval of weak coherent states of light at telecommunication wavelengths using erbium ions doped into a solid, using two photon-echo-based quantum storage protocols.
Abstract: We report experimental storage and retrieval of weak coherent states of light at telecommunication wavelengths using erbium ions doped into a solid. We use two photon-echo-based quantum storage protocols. The first one is based on controlled reversible inhomogeneous broadening (CRIB). It allows the retrieval of the light on demand by controlling the collective atomic coherence with an external electric field, via the linear Stark effect. We study how atoms in the excited state affect the signal-to-noise ratio of the CRIB memory. Additionally we show how CRIB can be used to modify the temporal width of the retrieved light pulse. The second protocol is based on atomic frequency combs. Using this protocol we verify that the reversible mapping is phase preserving by performing an interference experiment with a local oscillator. These measurements are enabling steps toward solid-state quantum memories at telecommunication wavelengths. We also give an outlook on possible improvements.

60 citations


Journal ArticleDOI
TL;DR: It is found that the frequency measurement of the emitted light localizes the atom in half-wavelength domain and the probability of finding the atom at a particular position can reach 100% when a photon with certain frequency is detected.
Abstract: We propose a scheme for two-dimensional (2D) atom localization based on the controlled spontaneous emission, in which the atom interacts with two orthogonal standing-wave fields. Due to the spatially dependent atom-field interaction, the position probability distribution of the atom can be directly determined by measuring the resulting spontaneously emission spectrum. The phase sensitive property of the atomic system leads to quenching of the spontaneous emission in some regions of the standing-waves, which significantly reduces the uncertainty in the position measurement of the atom. We find that the frequency measurement of the emitted light localizes the atom in half-wavelength domain. Especially the probability of finding the atom at a particular position can reach 100% when a photon with certain frequency is detected. By increasing the Rabi frequencies of the driving fields, such 2D sub-half-wavelength atom localization can acquire high spatial resolution.

58 citations


Proceedings ArticleDOI
12 Feb 2011
TL;DR: This paper begins with a state-of-the-art non-atomic MOEFSI protocol and demonstrates that an atomic implementation is much simpler while imposing less than a 2% performance penalty, and shows how to add support for speculative coherence and improve performance by up to 70% in the absence of races.
Abstract: This paper advocates Atomic Coherence, a framework that simplifies cache coherence protocol specification, design, and verification by decoupling races from the protocol's operation. Atomic Coherence requires conflicting coherence requests to the same addresses be serialized with a mutex before they are issued. Once issued, requests follow a predictable race-free path. Because requests are guaranteed not to race, coherence protocols are simpler and protocol extensions are straightforward. Our implementation of Atomic Coherence uses optical mutexes because optics provides very low latency. We begin with a state-of-the-art non-atomic MOEFSI protocol and demonstrate that an atomic implementation is much simpler while imposing less than a 2% performance penalty. We then show how, in the absence of races, it is easy to add support for speculative coherence and improve performance by up to 70%. Similar performance gains may be possible in a non-atomic protocol, but not without considerable effort in race management.

46 citations


Journal ArticleDOI
TL;DR: A new nonlinear optical process that occurs in a cloud of cold atoms at low-light-levels when the incident optical fields simultaneously polarize, cool, and spatially-organize the atoms is reported, which provides a new tool for in-situ monitoring of the atomic momentum distribution in an optical lattice.
Abstract: We report a new nonlinear optical process that occurs in a cloud of cold atoms at low-light-levels when the incident optical fields simultaneously polarize, cool, and spatially-organize the atoms. We observe an extremely large effective fifth-order nonlinear susceptibility of χ(⁵) = 7.6 × 10⁻¹⁵ (m/V)⁴, which results in efficient Bragg scattering via six-wave mixing, slow group velocities (∼ c/10⁵), and enhanced atomic coherence times (> 100 μs). In addition, this process is particularly sensitive to the atomic temperatures, and provides a new tool for in-situ monitoring of the atomic momentum distribution in an optical lattice. For sufficiently large light-matter couplings, we observe an optical instability for intensities as low as ∼ 1 mW/cm² in which new, intense beams of light are generated and result in the formation of controllable transverse optical patterns.

36 citations


Journal ArticleDOI
TL;DR: Discrimination of the effect of one-photon and two-Photon coherences in electromagnetically induced transparency for a three-level ladder-type atomic system and found that the spectra showed peaks as the branching ratio of the intermediate (excited) state increased (decreased).
Abstract: We present discrimination of the effect of one-photon and two-photon coherences in electromagnetically induced transparency for a three-level ladder-type atomic system. After the optical Bloch equations for a three-level atom, with either cycling or non-cycling transitions, were solved numerically, the solutions were averaged over the velocity distribution and finite transit time. Through this we were able to discriminate one-photon and two-photon coherence parts of the calculated spectra. We also found that the spectra showed peaks as the branching ratio of the intermediate (excited) state increased (decreased). The experimental results of previous reports [H. S. Moon, et al., Opt. Express 16, 12163 (2008); H. S. Moon and H. R. Noh, J. Phys. B 44, 055004 (2011)] could well be accounted for by this discrimination of one-photon and two-photon coherences in the transmittance signals for the simplified three-level atomic system.

34 citations


Journal ArticleDOI
TL;DR: In this paper, a quantum memory process based on the conversion of a signal pulse into a long-lived spin coherence via light matter interaction in an on-resonant -type system is studied.
Abstract: We study the coherent storage and retrieval of a very short multimode light pulse in an atomic ensemble. We consider a quantum memory process based on the conversion of a signal pulse into a long-lived spin coherence via light matter interaction in an on-resonant � -type system. In order to study the writing and reading processes we analytically solve the partial differential equations describing the evolution of the field and of the atomic coherence in time as well as in space. We show how to optimize the process for writing as well as for reading. If the medium length is fixed, for each length, there is an optimal value of the pulse duration. We discuss the information capacity of this memory scheme and we estimate the number of transverse modes that can be stored as a quantum hologram.

28 citations


Journal ArticleDOI
TL;DR: Electromagnetically induced absorption (EIA) with sub-kHz spectral width in a paraffin-coated Rb vapor cell in the Hanle configuration of the 5S(1/2)(F=2)-5P(3/ 2)(F'=3) transition of 87Rb atoms is reported on.
Abstract: We report on electromagnetically induced absorption (EIA) with sub-kHz spectral width in a paraffin-coated Rb vapor cell in the Hanle configuration of the 5S1/2(F=2)-5P3/2(F’=3) transition of 87Rb atoms. Using a linearly polarized laser, the spectral width of the Hanle EIA spectrum was measured to be 0.55 mG (390 Hz). The narrow spectral width was due to the maintaining of atomic coherence between ground states while atoms collided with the anti-relaxation coated wall of the Rb vapor cell. Under a weak transverse residual magnetic field, the angle between the transverse residual magnetic field and the direction of linear polarization affected the magnitude of the narrow Hanle EIA spectrum. This is because of the change of atomic magnetic momentum due to the weak transverse residual magnetic field around the zero value of the longitudinal magnetic field.

27 citations


Journal ArticleDOI
TL;DR: In this paper, a quantum memory scheme based on controlled de-and rephasing of atomic coherence of a nonresonant, inhomogeneously broadened Raman transition is examined.
Abstract: We examine a quantum memory scheme based on controlled de- and rephasing of atomic coherence of a nonresonant, inhomogeneously broadened Raman transition. We show that it generalizes the physical conditions for time-reversible interaction between light and atomic ensembles in the case of strong fields and nonlinear interactions. Furthermore, assuming weak input fields, we develop a unified framework for realizations exploiting either controlled reversible inhomogeneous broadening or atomic frequency combs, and discuss new aspects of the storage and manipulation of quantum states.

Journal ArticleDOI
Abstract: We have investigated the optical pumping effects of single-resonance optical pumping (SROP) and double-resonance optical pumping (DROP) in the ladder-type electromagnetically induced transparency (EIT) of the 5S1/2–5P3/2–5D3/2 transition of 87Rb atoms. In the 5S1/2(F = 2)–5P3/2(F' = 3)–5D3/2(F'' = 2, 3) transition with the single-resonance cycling 5S1/2(F = 2)–5P3/2(F' = 3) transition, we observed the transmittance spectrum due to DROP and EIT. Based on our experimental results investigated according to the laser power (the probe and the coupling) and the coupling laser detuning, we revealed that DROP was significant for the transmittance spectrum. Particularly, in the 5S1/2(F = 2)–5P3/2(F' = 1, 2)–5D3/2(F'' = 1) transition without a cycling transition, we observed the two-photon absorption due to two-photon atomic coherence, when the probe laser power was weak and the coupling laser power was strong.

Journal ArticleDOI
TL;DR: In this article, a scheme to generate stable three-dimensional spatiotemporal optical solitons, or ultraslow optical bullets, at very low light levels via atomic coherence was proposed.
Abstract: We propose a scheme to generate stable ultraslow three-dimensional spatiotemporal optical solitons, or ultraslow optical bullets, at very low light levels via atomic coherence. The system we consider is an ensemble of resonant, lifetime-broadened N-type four-level atoms, working in a regime of electromagnetically induced transparency. Due to the quantum interference effect induced by a control field, the absorption of a probe field is largely suppressed. Moreover, the Kerr nonlinearity is greatly enhanced, and the dispersion property of the probe field is drastically changed. Using a method of multiple scales, we derive two coupled nonlinear envelope equations controlling the evolution of the envelopes of the probe field and an assisted field. We show that under certainconditionstheenvelopeoftheprobefieldsatisfiesathree-dimensionalnonlinearSchr¨ odingerequationand the envelope of the assisted field obeys a linear Helmholtz equation. We obtain various optical bullet solutions for the probe-field envelope and demonstrate that such optical bullets have many novel features, including very slow propagating velocity and very low generation power. In addition, they can be actively controlled and manipulated by adjusting system parameters. The stabilization of the optical bullets obtained can be easily realized by the trapping potential contributed by the assisted field, which is also investigated in detail.

Journal ArticleDOI
Jun Kou1, Ren-Gang Wan1, Zhi-Hui Kang1, L. Jiang1, Lei Wang1, Yuanfei Jiang1, Jinwu Gao1 
TL;DR: In this article, a scheme for achieving phase-dependent coherent population trapping was proposed, showing that both the dark state of the atoms and light propagation dynamics depend on the relative phase of the fields.
Abstract: We propose a scheme for achieving phase-dependent coherent population trapping, showing that both the dark state of the atoms and light propagation dynamics depend on the relative phase of the fields. The atomic coherence prepared via adiabatic process plays a key role in the interaction of light with matter. And an optical switching based on the phase-controlled quantum interference is implemented, which may have potential application in high-speed optical communications and quantum information systems.

Journal ArticleDOI
TL;DR: In this article, a Doppler broadened multi-level system for the D2 line of 85Rb atoms in a vapour cell considering different types of atom-laser coupling schemes is presented.
Abstract: Atomic coherence resonances such as electromagnetically induced transparency (EIT) and electromagnetically induced absorption (EIA) signals are observed in a Doppler broadened multi-level system for the D2 line of 85Rb atoms in a vapour cell considering different types of atom–laser coupling schemes. Besides the coherence resonances, the nonlinear resonances like velocity selective optical pumping (VSOP) dips and velocity selective resonances (VSR) are also observed for the non-zero velocity selective groups of atoms. In the presence of pump, control and probe laser fields, we observe two EIT signals in a double Λ-type system and two EIA signals in a double V-type system. We are able to see the EIA signal for the non-zero velocity group of atoms when the pump laser is locked with an open transition by a small red detuning. We also report the experimental observation of simultaneous EIT and EIA signals in a (Λ+V)-type system. The effect of frequency tuning of the control laser is also studied in the presence of the frequency locked pump laser. A simple theoretical analysis explains the experimental results.

Journal ArticleDOI
TL;DR: In this article, a general model for an atomic memory using ultra-short pulses of light, which allows both spatial and temporal multimode storage, is presented, which is valid for any frequency detuning, from the resonant case to the Raman case, and allows a detailed optimization of the memory efficiency.
Abstract: We present a general model for an atomic memory using ultra-short pulses of light, which allows both spatial and temporal multimode storage. The process involves the storage of a faint quantum light pulse into the spin coherence of the ground state of Lambda-type 3-level atoms, in the presence of a strong driving pulse. Our model gives a full description of the evolution of the field and of the atomic coherence in space and time throughout the writing and the read-out processes. It is valid for any frequency detuning, from the resonant case to the Raman case, and allows a detailed optimization of the memory efficiency.

Journal ArticleDOI
Bing Zhang1, Jin-Hui Wu1, Xi-Zhang Yan1, Lei Wang1, Xiao-Jun Zhang1, Jin-Yue Gao1 
TL;DR: A new scheme for achieving the complete population transfer and the optimal coherence generation between the ground state and the Rydberg state in a four-level ladder system by combining the STirAP or fractional STIRAP technique and the π pulse technique is proposed.
Abstract: We propose a new scheme for achieving the complete population transfer and the optimal coherence generation between the ground state and the Rydberg state in a four-level ladder system by combining the STIRAP or fractional STIRAP technique and the π pulse technique. We consider, in particular, two different situations where spontaneous emission from the two highest states are neglected or not. Our numerical calculations show that the time width and the delay time of the π pulse are two critical parameters for attaining the maximal population transfer and coherence generation in this scheme.

Journal ArticleDOI
TL;DR: The two- and three-pulse photon echo emission from a scattering powder, obtained by grinding a Pr3+:Y2SiO5 rare earth doped single crystal, is observed and it is shown that the collective emission is coherently constructed over several grains.
Abstract: We observe the two- and three-pulse photon echo emission from a scattering powder, obtained by grinding a Pr3+:Y2SiO5 rare earth doped single crystal We show that the collective emission is coherently constructed over several grains A well defined atomic coherence can therefore be created between randomly placed particles Observation of photon echo on powders as opposed to bulk materials opens the way to faster material development More generally, time-domain resonant four-wave mixing offers an attractive approach to investigate coherent propagation in scattering media

Journal ArticleDOI
TL;DR: In this article, the enhancement and suppression of two coexisting six-wave mixing (SWM) processes via atomic coherence have been observed, where the self-dressing effect causes the Autler-Townes (AT) splitting of the SWM signals and the external dressing effect makes the external SWM signal enhanced or suppressed.
Abstract: The enhancement and suppression of the two coexisting six-wave mixing (SWM) processes via atomic coherence have been observed. In the presence of mutual dressing between two SWM signals, the self-dressing effect causes the Autler-Townes (AT) splitting of the SWM signals and the external-dressing effect makes the SWM signals enhanced or suppressed. In addition, the power dependencies of the enhancement and suppression of SWM processes are studied. Theoretical calculations are carried out, which are in good agreement with the experimental results.

Journal ArticleDOI
TL;DR: In this article, the authors studied the dynamics of entanglement of two initially separate atoms passing through a cavity one after another by employing concurrence and negativity, and the effects of the atomic coherence and mean photon number on the time evolution of atom-atom entaglement are examined when the field is initially in thermal field.

Journal ArticleDOI
TL;DR: In this paper, the authors proposed a scheme to realize a transition from delocalization to localization of light waves via electromagnetically induced transparency, which is a resonant cold atomic ensemble having $N$ configuration, with a control field consisting of two pairs of laser beams with different cross angles.
Abstract: We propose a scheme to realize a transition from delocalization to localization of light waves via electromagnetically induced transparency. The system we suggested is a resonant cold atomic ensemble having $N$ configuration, with a control field consisting of two pairs of laser beams with different cross angles, which produce an electromagnetically induced quasiperiodic waveguide (EIQPW) for the propagation of a signal field. By appropriately tuning the incommensurate rate or relative modulation strength between the two pairs of control-field components, the signal field can exhibit the delocalization-localization transition as it transports inside the atomic ensemble. The delocalization-localization transition point is determined and the propagation property of the signal field is studied in detail. Our work provides a way of realizing wave localization via atomic coherence, which is quite different from the conventional, off-resonant mechanism-based Aubry-Andre model, and the great controllability of the EIQPW also allows an easy manipulation of the delocalization-localization transition.

Journal ArticleDOI
TL;DR: In this paper, the authors proposed a scheme to generate high-dimensional self-trapped laser beams at a very low light intensity via atomic coherence via a resonant four-level atomic ensemble, working in an active Raman gain regime and at room temperature.
Abstract: We propose a scheme to generate high-dimensional self-trapped laser beams at a very low light intensity via atomic coherence. The system we consider is a resonant four-level atomic ensemble, working in an active Raman gain regime and at room temperature. We derive a high-dimensional nonlinear envelope equation for a signal field with a specific saturable nonlinearity. We show that because of the quantum interference effect induced by a control field, the imaginary part of the coefficients of the signal-field envelope equation can be much smaller than their real part. We demonstrate that the system supports gain-assisted, stable, high-dimensional spatial optical solitons and long-lifetime vortices, which can be produced with light power at the microwatt level.

Journal ArticleDOI
TL;DR: In this paper, a pair of broadband (Δλ∼20nm) and ultrashort pulses with a variable time delay excites the rubidium atoms into the 5D state from the ground state where the two-photon transitions are enhanced by the intermediate level 5P.
Abstract: We demonstrate temporal coherent control in two-photon transitions. A pair of broadband (Δλ∼20nm), ultrashort (Δt∼100fs), collinear pulses with a variable time delay excites the rubidium atoms into the 5D state from the 5S ground state where the two-photon transitions are enhanced by the intermediate level 5P. The excited atoms radiate 5μm (5D–6P) and 420nm (6P–5S) light. As a result of tuning the wavelength of the input laser, a superfluorescence at 420nm exhibits different temporal behaviors. A switching from a beating at the frequency given by the difference between the sequential atomic transitions that involve the 5P3/2 intermediate level, to a quantum beating due to two different two-photon excitation paths, 5S→5P1/2→5D and 5S→5P3/2→5D is observed. Based on the simple atom-field interaction theory, an analytic solution, which qualitatively elucidates experimental results, is obtained.

Journal ArticleDOI
TL;DR: In this paper, an atomic diffraction grating that combines an electromagnetically induced grating with a coherence grating in a double-energy atomic system was proposed.
Abstract: We describe theoretically an atomic diffraction grating that combines an electromagnetically induced grating with a coherence grating in a double-$\ensuremath{\Lambda}$ atomic system With the atom in a condition of maximal coherence between its lower levels, the combined gratings simultaneously diffract both the incident probe beam as well as the signal beam generated through four-wave mixing A special feature of the atomic grating is that it will diffract any beam resonantly tuned to any excited state of the atom accessible by a dipole transition from its ground state

Journal ArticleDOI
TL;DR: In this paper, a nondegenerate phase-conjugate wave was generated via stored atomic coherence in a Pr{sup 3+}:Y{sub 2}SiO{sub 5} crystal based on the electromagnetically induced transparency effect, and its capability for wavefront reconstruction of phase distortion was demonstrated experimentally.
Abstract: A nondegenerate phase-conjugate wave was generated via stored atomic coherence in a Pr{sup 3+}:Y{sub 2}SiO{sub 5} crystal based on the electromagnetically induced transparency effect, and its capability for wave-front reconstruction of phase distortion was demonstrated experimentally. The phase-matching condition during the storage-retrieval process of the phase-conjugate wave was characterized both experimentally and theoretically in detail. Theoretical simulations fit the experimental data very well. Such a scheme of storage and retrieval of the phase-conjugate wave may have potential applications in optical signal processing and information security.

Journal ArticleDOI
TL;DR: In this paper, the electromagnetically induced transparency (EIT) and its dispersion properties in a four-level inverted-Y atomic system are investigated, and the absorption spectrum of a weak probe field shows two EIT windows (dark resonances) whose location, width, and depth can be controlled by manipulating the parameters of the coupling fields.

Journal ArticleDOI
TL;DR: In this article, a method for the preparation of atomic coherence in a high density atomic medium, utilising a coherent preparation scheme of gigahertz bandwidth pulses, is presented.
Abstract: We detail a method for the preparation of atomic coherence in a high density atomic medium, utilising a coherent preparation scheme of gigahertz bandwidth pulses. A numerical simulation of the preparation scheme is developed, and its efficiency in preparing coherent states is found to be close to unity at the entrance to the medium. The coherence is then measured non-invasively with a probe field.

Journal ArticleDOI
TL;DR: In this article, experimental observations of interference between an atomic spin coherence and an optical field in a gradient echo memory are presented. But the interference is mediated by a strong classical field that couples a weak probe field to the atomic coherence through a resonant Raman transition.
Abstract: We present experimental observations of interference between an atomic spin coherence and an optical field in a {\Lambda}-type gradient echo memory. The interference is mediated by a strong classical field that couples a weak probe field to the atomic coherence through a resonant Raman transition. Interference can be observed between a prepared spin coherence and another propagating optical field, or between multiple {\Lambda} transitions driving a single spin coherence. In principle, the interference in each scheme can yield a near unity visibility.

Journal ArticleDOI
TL;DR: In this paper, the interplay among coexisting multi-wave-mixing (MWM) signals via multiple electromagnetically induced transparency (EIT) windows, including two ladder-type EIT windows and one V-like window in a five-level atomic system of Rb85, was observed.
Abstract: We experimentally observe the interplay among coexisting multiwave-mixing (MWM) signals via multiple electromagnetically induced transparency (EIT) windows, including two ladder-type EIT windows and one V-type EIT-like window in a five-level atomic system of Rb85. In the presence of these EIT windows, one can control the interplay between these MWM signals easily by changing the frequency detuning. Meanwhile, we also report the spatial and temporal interferences with a femtosecond time scale among three coexisting MWM signals in two overlapped EIT windows.

Journal ArticleDOI
TL;DR: Observations on enhancement and suppression of spatial four-wave mixing (FWM) images and the interplay of four coexisting FWM processes in a two-level atomic system associating with three- level atomic system as comparison are reported.
Abstract: We report our observations on enhancement and suppression of spatial four-wave mixing (FWM) images and the interplay of four coexisting FWM processes in a two-level atomic system associating with three-level atomic system as comparison. The phenomenon of spatial splitting of the FWM signal has been observed in both x and y directions. Such FWM spatial splitting is induced by the enhanced cross-Kerr nonlinearity due to atomic coherence. The intensity of the spatial FWM signal can be controlled by an additional dressing field. Studies on such controllable beam splitting can be very useful in understanding spatial soliton formation and interactions, and in applications of spatial signal processing.