************************************ * QUANTUM OPTICS AND ATOM OPTICS * * IN AUSTRALASIA * * * * * * * * MONTHLY NEWSLETTER * * VOL IV, NO 2/3 * * * CONTENTS: * Feb/March 1996 * ________________ * * * ISSN 1325-6467 * 1. ABSTRACTS * * Edited by: Craig Savage 2. CONFERENCES * \ | / * Physics, Faculties, ANU, * \__|__/ * ACT 0200, Australia. * | * email: Craig.Savage@anu.edu.au Available on WWW at: * | * fax: +61 [(0)6] 249 0741 http://www.anu.edu.au * | * voice: +61 [(0)6] 249 4202 /Physics/newsletter * * ___________________ Thanks for the flood of abstracts in response to my request. I think you'll agree that they're better in smaller doses, so please remember to send in abstracts when you submit papers. ___________________ 1. ABSTRACTS ____________ TITLE: Parametric test of quantum mechanics vs. macroscopic local realism AUTHORS: S. Chaturvedi and P.D. Drummond STATUS: Submitted ABSTRACT: We identify a new test of quantum mechanics versus macroscopic local realism, using the steady-state triple quadrature correlations of a parametric oscillator below threshold. ____________ TITLE: Manipulating beams of ultra-cold atoms with a static magnetic field AUTHORS: W J Rowlands, D C Lau, G I Opat, A I Sidorov, R J McLean, P Hannaford. STATUS: Aust. J. Phys. Vol. 49, p. 577 (1996). ABSTRACT: We report preliminary results on the deflection of a beam of ultra cold atoms by a static magnetic field. Caesium atoms trapped in a magneto-optical trap are cooled using optical molasses, and then fall freely under gravity to form a beam of ultra-cold atoms. The atoms pass through a static inhomogeneous magnetic field produced by a single current-carrying wire, and are deflected by a force grad(mu.B) dependent on the magnetic substate of the atom. The population of atoms in various magnetic substates can be altered using resonant laser radiation to optically pump the atoms. ____________ TITLE: Magnetostatic state-selective deflection of a beam of laser-cooled atoms AUTHORS: W J Rowlands, D C Lau, G I Opat, A I Sidorov, R J McLean, P Hannaford. STATUS: Accepted Optics Communication ABSTRACT: We have demonstrated the transverse state-selective deflection of a beam of free-falling laser-cooled caesium atoms by the inhomogeneous static magnetic field of a current-carrying wire. With currents of up to 45 A the positions of atoms in individual magnetic substates are clearly resolved and deflection angles as large as 25 degrees are observed. By optically pumping the atoms toward the m_F=+4 substate in the ground state, most of the atoms are deflected through the same angle. The current-carrying wire can be considered as a simple magnetostatic atomic-optical element. ____________ TITLE: Specular reflection of cold caesium atoms from a magnetostatic mirror AUTHORS: A I Sidorov, R J McLean, W J Rowlands, D C Lau, J E Murphy, M Walkiewicz, G I Opat, and P Hannaford. STATUS: Accepted Semiclassical and Quantum Optics ABSTRACT: We have observed specular reflection and multiple bounces of a beam of laser-cooled caesium atoms from a magnetostatic mirror consisting of an array of rare-earth permanent magnets. Using a time-of-flight technique, the reflection coefficient of the mirror for caesium 6 ^2S_1/2, F=+4 atoms pumped toward the m=+4 state is determined to be (100+/-2)%. For a beam of unpolarised atoms the reflectivity is found to be unexpectedly high, (90+/-5)%, which is attributed to contributions from atoms in m=0,-1,-2 states which are reflected at high magnetic fields close to the surface of the mirror as a result of the quadratic Zeeman effect. ____________ TITLE: Second Order Interference in Two Photon Absorption AUTHORS: M.W. Hamilton and D.S. Elliott ADDRESS: Physics and Mathematical Physics, University of Adelaide, Adelaide SA5005, Australia, and School of Electrical and Computer Engineering, Purdue University, W. Lafayette, Indiana 47907, U.S.A. STATUS: J Mod. Optics, Almost submitted ABSTRACT: Two photon absorption is considered in the context of second order coherence measurements. We examine second order interference fringes for the typical Doppler free spectroscopic layout which involves a retroreflecting mirror. The fringes are manifested in the wings of the absorption spectrum and their observability requires partial decoherence of the exciting laser light. ____________ TITLE: Quantum manipulation of a Bose-Einstein condensate by light waves AUTHORS: Heping Zeng, Fucheng Lin and Weiping Zhang STATUS: Physics Letters A 201, 397 (1995) ABSTRACT: A scheme to manipulate the quantum statistical properties of a neutral atomic Bose-Einstein condensate by quantized light fields is proposed. ____________ TITLE: Nonclassical Bose-Einstein condensate AUTHORS: Heping Zeng, Weiping Zhang and Fucheng Lin STATUS: Physical Review A 52, 2155 (1995) ABSTRACT: A scheme is proposed to manipulate the quantum statistical properties of a neutral atomic Bose-Einstein condensate in an ultrocold alkali-atom-trap with atoms in the ground hyperfine F=1, MF=-1,0,+1 states. Initially, the atomic condensate is assumed to be prepared in a hyperfine sublevel |-1>. By effective two-photon excitations with two sigma+ and sigma- nonresonant copropagating travelling wave light fields, we show that the atomic system can be settled into a coherent superposition of two atomic Bose-Einstein condensates corresponding to different ground hyperfine sublevels and different quantum statistics. Furthermore, with an appropriate choice of interaction time, atom-field coupling strengths and quantum features of the laser field, a nonclassical condensate can be prepared in the hyperfine sublevel |+>. ____________ TITLE: Bosonic-degeneracy-induced quantum correlation in a nonlinear atomic beam splitter AUTHORS: Weiping Zhang and D. F. Walls STATUS: Physical Review A 52, 4696 (1995) ABSTRACT: We employ a vector field theory to describe the interaction of a coherent atomic beam with a standing wave laser field. The coherent atomic beam is assumed to be composed of degenerate bosonic atoms. We derive a nonlinear Schrodinger equation to describe the diffraction of the coherent atomic beam through the standing-wave laser field in the adiabatic regime of interaction of atoms with a light wave. Under appropriate conditions, we find that the standing wave laser field acts as a qunatum nonlinear atomic beam splitter for a coherent atomic beam. The quantum correlation in the nonlinear atomic beam splitter are analysed and the analogy to quantum correlations of nonclassical light in an optical Kerr-type medium is discussed. ____________ TITLE: Atomic self-focussing in a light "medium" AUTHORS: Weiping Zhang and B. C. Sanders STATUS: To be submitted and preprints are available ABSTRACT: Light-induced dipole-dipole interaction in a coherent atomic field results in an effective nonlinearity for atoms. This nonlinearity can induce self-focussing of a coherent atomic beam undergoing propagation through a travelling wave laser beam; we show how such a scheme could be realised and evaluate the critical atomic density required for atomic self-focussing. ____________ TITLE: Vector quantum field theory of atoms: Nonlinear atom optics and Bose-Einstein condensate AUTHORS: Weiping Zhang STATUS: Accepted Australian Journal of Physics ABSTRACT: The recent experimental progress in laser cooling and trapping of neutral atoms brings the atomic samples into the ultracold regime where the bosonic atoms and fermonic atoms are expected to have different dynamic behaviours in the laser fields. In this paper, we systematically introduce the theoretical study of interaction of an ultracold atomic ensamble with a light wave in the frame of a vector quantum field theory. The many-body quantum correlation in the ultracold regime of atom optics is studied in terms of the vector quantum field theory. A general formalism of nonlinear atom optics for a coherent atomic beam is developed. ____________ TITLE: Generation of squeezed light via spontaneous emission from a three-level cascade system. AUTHORS: M R Ferguson, Z Ficek and B J Dalton STATUS: Accepted Optics Communications ABSTRACT: A theoretical investigation is made into the possibility of generating squeezed states of light in spontaneous emission from a three-level atom. Spontaneous emission is known as a source of the noise which destroys coherence effects. We find that rather than destroy squeezing, spontaneous emission from a three-level cascade system can actually create squeezing in an initially unsqueezed source field provided the atom is initially prepared in a suitable superposition of its states. We show that the ability of a three-level atom to generate squeezing of the source field via spontaneous emission relies on the presence of non-zero two-photon coherences that are not present in two-level atoms, in which source field squeezing only occurs if it is present initially. ____________ TITLE: Probe Absorption Spectra For Driven Atomic Systems In a Narrow Bandwidth Squeezed Vacuum AUTHORS: M. Bosticky, Z. Ficek and B. J. Dalton STATUS: Accepted Physical Review A ABSTRACT: The behaviour of a three level atom in a cascade configuration with the lower transition coherently driven and also coupled to a narrow bandwidth squeezed vacuum field is studied. A master equation treatment based on dressed atom states is used and expressions for probe absorption spectra obtained via linear response theory and the quantum regression theorem. The expressions obtained also apply to the broad bandwidth squeezed vacuum case. Numerical studies of the modifications caused by the finite squeezed vacuum bandwidth to the Mollow and Autler-Townes probe absorption spectra are made for the case where the squeezed vacuum field centre frequency and the driving laser frequency coincide and where upper transition relaxation terms are ignored. The squeezed vacuum source is assumed to be a degenerate parametric amplifier for the numerical calculations. Cases where the driving laser is resonant and detuned are examined. The spectral features are sensitively dependent on the phase of the squeezed vacuum field for a given driving laser phase. Dispersive features in the Mollow probe absorption spectrum can become absorptive, and vice versa. It is found in the probe absorption spectra that for certain choices of the squeezed vacuum phase, lines narrower than for the broad band squeezed vacuum are obtained in the finite bandwidth situation. In both the Mollow and Autler-Townes spectra features narrower than for the normal vacuum case are obtained when the laser field is detuned, and in the Autler-Townes case this occurs for resonance also. ____________ TITLE: Hole burning and dispersive profiles at line centre of the probe absorption spectrum of a two-level atom in a squeezed vacuum AUTHORS: Peng Zhou, Z. Ficek, and S. Swain ADDRESS: Department of Applied Mathematics and Theoretical Physics, The Queen's University of Belfast, Belfast BT7 1NN, U. K. STATUS: Accepted JOSA B ABSTRACT: We study the absorption spectra of a weak probe beam which interacts with a driven two--level atom in the prescence of a squeezed vacuum. In particular, we focus on the behaviour of the central resonance of the probe absorption spectra in the region of intermediate driving intensities and in the large squeezed photon number limit. Squeezing--induced pimples, hole--burning and dispersive profiles at line centre are displayed. These unusual spectral features are very sensitive to the squeezing phase and the Rabi frequency of the driving field. We present analytic conditions for the occurrence of these effects, and find that they all take place in the vicinity of the critical point dividing the different dynamical regimes, probe absorption and amplification, of the atomic radiation. We also investigate analytically and numerically the two--time correlation functions of the atomic polarization, and find that the cross--correlations of the two dipole quadratures contribute symmetric (absorption--like) spectral features to the absorption spectra, whilst the self--correlations contribute asymmetric (dispersion--like) spectral profiles, which disappear for the particular phase values $\Phi =0,\,\pi $. The physical origin of the unusal spectral profiles at line centre is also discussed in terms of the coherent population oscillations. ____________ &&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&& 2. CONFERENCES ________________ Quantum Optics Meeting - Satellite Meeting to IQEC '96 8-9 July 1996 Novotel Palm Cove Resort, Cairns, North Queensland, Australia This two-day meeting on Quantum Optics will be a satellite meeting to IQEC'96. It will take place at Novotel Palm Cove Resort, Cairns, North Queensland on Monday 8 and Tuesday 9 July, in the week before the IQEC Meeting in Sydney (14-19 July). The meeting will overlap with the three-day meeting on Atom Optics to be held at the same venue on Tuesday 9, Wednesday 10 and Thursday 11 July. For more details (including registration form) see http://www.physics.uq.oz.au:8001/conference/welcome.html ________________ Atom Optics Meeting- Satellite Meeting to IQEC '96 9-11 July 1996 Novotel Palm Cove Resort, Cairns, North Queensland, Australia This three-day workshop on Atoms Optics and Interferometry will be a satellite meeting to IQEC `96. The workshop will overlap with the two-day workshop on Quantum Optics to be held at the same venue on Monday 8, and Tuesday 9 July. For more details see: http://www.anu.edu.au/Physics/Cairns96/ &&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&