************************************ * QUANTUM OPTICS AND ATOM OPTICS * * IN AUSTRALASIA * * * * * * * * MONTHLY NEWSLETTER * * VOL IV, NO 10 * * * * November 1996 * * * * ISSN 1325-6467 * * * Edited by: Murray Hamilton * \ | / * Physics, University of Adelaide, * \__|__/ * SA 5005, Australia. * | * email: mwh@physics.adelaide.edu.au Available on WWW at: * | * fax: +61 8 8303 5322 http://www.anu.edu.au * | * voice: +61 8 8232 6541 /Physics/newsletter * * ___________________ A new Editor: Craig has passed on the mantle and I will be looking after the newsletter for a while at least. The newsletters will still be archived at the ANU site shown above, for the next few months. ------------------------------------------------------------------------------ CONTENTS 1. ABSTRACTS 2. CONFERENCE ANNOUNCEMENTS 3. WANTED TO BUY 4. SITUATIONS VACANT ______________________________________________________________________________ ___________________ 1. ABSTRACTS TITLE: Correcting the effects of spontaneous emission on cold trapped ions AUTHORS: C. D'Helon and G.J. Milburn ADDRESS: Department of Physics, University of Queensland EMAIL: dhelon@physics.uq.oz.au JOURNAL: STATUS: submitted ABSTRACT: We propose two quantum error correction schemes which increase the maximum storage time for qubits in a system of cold trapped ions, using a minimal number of ancillary qubits. Both schemes consider only the errors introduced by the decoherence due to spontaneous emission from the upper levels of the ions. A watchdog approach is adopted in conjunction with selective coherent feedback to eliminate these errors immediately following spontaneous emission events. http://xxx.lanl.gov/abs/quant-ph/9610031 ______________________________________________________________________________ TITLE: The quantum Zeno effect in atomic Bragg scattering AUTHORS: S. Dyrting and M. J. Gagen ADDRESS: Department of Physics, University of Queensland EMAIL: dyrting@maxwell.physics.uq.oz.au JOURNAL: Physical Review A STATUS: submitted ABSTRACT: We propose an experiment to observe the quantum Zeno effect in atomic Bragg scattering. The quantum Zeno effect is the inhibition of the free evolution of a system when that system is subject to a decohering measurement process. This effect is usually studied theoretically in an idealized two-level system, though this system has been difficult to realize in practice. The coherent population exchange between the forward and Bragg beams provides an ideal two-level system, though as there is no practical scheme for continuously monitoring the motion of an atom we include decoherence by adding noise to the laser. Using the method of stochastic Hamiltonians we show that the noise suppresses tunneling in the two-state system and, in the large noise limit, the system can freeze in its initial state. _____________________________________________________________________________ TITLE: Optimal detection strategies for measuring the stochastic gravitational radiation background with laser interferometric antennas AUTHORS: Nelson Christensen ADDRESS: Department of Physics, University of Auckland, Auckland, New Zealand EMAIL: nlc@phy.auckland.ac.nz JOURNAL: Phys. Rev. D. STATUS: accepted for publication ABSTRACT: Issues pertaining to the optimal strategy for detecting the stochastic gravitational wave background (SGWB) with laser interferometric antennas are discussed. Analyzed are the dependence of detection sensitivity on the relative orientation of interferometers, the interferometer design, and the inherent noise of the detectors. Previously Michelson, Flanagan and Christensen thoroughly studied such topics. This paper addresses a few remaining issues for the optimal detection of the SGWB with laser interferometers. The optimal orientation of a pair of interferometers depends on both the noise characteristics of the detectors and their physical location on the surface of the Earth. Given a pair of detectors the maximum sensitivity for detecting the SGWB also depends on the transfer function of the interferometers; the relatively narrow band dual recycling interferometers are the best choice. Correlated noise in two antennas located at a single site complicates the detection strategy, but an optimistic attitude is called for given the considerable relative size of the correlated signal. The Laser Interferometric Gravitational Wave Observatory offers exciting prospects for placing limits on the strength of the SGWB. ------------------------------------------------------------------------------ TITLE: Low Noise Amplification and Efficient Squeezing from Rate Matched Lasers. AUTHORS: T.C.Ralph ADDRESS: Department of Physics, Faculty of Science The Australian National University, ACT 0200, Australia EMAIL: Timothy.Ralph@anu.edu.au JOURNAL: Phys. Rev. A. STATUS: submitted ABSTRACT: We investigate the quantum noise properties of lasers in which both the laser and pump form resonant cavity modes. We find that under conditions typical of solid-state lasers small signals placed on the pump beam of such systems can be found to be amplified on the laser output without incurring the usual 3 dB noise penalty associated with linear amplifiers. We also show that such systems can be very efficient producers of squeezed light. ______________________________________________________________________________ TITLE: Quantum Phenomena in Optical Interferometry AUTHORS: P. Hariharan and B. C. Sanders JOURNAL: Progress in Optics STATUS: Vol. XXXVI, 1996 (in press) ______________________________________________________________________________ TITLE: Quantum signatures of chaos in the dynamics of a trapped ion BY: J.K. Breslin, C. A. Holmes and G.J. Milburn SUBMITTED TO: Phys Rev A. ABSTRACT: We show how a nonlinear chaotic system, the parametrically kicked nonlinear oscillator, may be realised in the dynamics of a trapped, laser-cooled ion, interacting with a sequence of standing wave pulses. Unlike the original optical scheme [G.J.Milburn and C.A.Holmes, Phys. Rev A, vol44, 4704, (1991) ],the trapped ion enables strongly quantum dynamics with minimal dissipation. This should permit an experimental test of one of the quantum signatures of chaos; irregular collapse and revival dynamics of the average vibrational energy. _____________________________________________________________________________ TITLE: Conditional variance reduction by measurements on correlated field modes. AUTHOR: J.K.Breslin, G.J.Milburn TO APPEAR: Phys Rev A. ABSTRACT: We consider the case of two cavity modes of the electromagnetic field which are coupled via the action of a parametric amplifier. The fields are allowed to leak from the cavity and homodyne measurement is performed on one of the modes. Because of the correlations between the modes, this leads to a reduction of the variance in a quadrature of the other mode, although no measurement is performed on it directly. We discusshow this relates to the Einstein-Podolsky-Rosen Gedankenexperiment ______________________________________________________________________________ TITLE: Optimal Quantum Trajectories for Discrete Measurements} BY: J.K.Breslin, G.J.Milburn SUBMITTED TO: J. Mod. OPtics. ABSTRACT: Using the method of quantum trajectories we show that a known pure state can be optimally monitored through time when subject to a sequence of discrete measurements. By modifying the way we extract information from the measurement apparatus we can minimise the average algorithmic information of the measurement record, without changing the unconditional evolution of the measured system. We define an optimal measurement scheme as one which has the lowest average algorithmic information allowed. We also show how it is possible to extract information about system operator averages for the measurement records and their probabilities. The optimal measurement scheme, in the limit of weak coupling, determines the statistics of the variance of the measured variable directly. We discuss the relevance of such measurements for recent experiments in quantum optics. ______________________________________________________________________________ TITLE: Noise and Fractional Quantum Revivals in the Atomic Gravitational Cavity BY: Wen-Yu Chen, S. Dyrting, G.J. Milburn. SUBMNITTED TO: Phys rev A. ABSTRACT: In this paper, we present a full discussion of the quantum dynamics and fractional quantum revivals of an integrable nonlinear system --- the atomic gravitational cavity including stochastic surface adsorption and spontaneous emission. The stochastic surface adsorption is modelled as a ``destructive" measurement of the position which is explicitly expressed in terms of quantum trajectories, while the spontaneous emission is treated as a stochastic process by means of stochastic Hamiltonians method. We find that the fractional quantum revivals are very sensitive to noise and can even be completely destroyed by strong noise. Surface adsorption is negligible when spontaneous emission is low, so the effective way of reducing noise is to reduce spontaneous emission by means of large detuning. Provided the detuning is big enough and the evanescent wave intensity is strong enough, the effect of spontaneous emission can be arbitrarily reduced so that the revivals remain well-resolved and can be experimentally observable. ______________________________________________________________________________ TITLE: Quantum information and correlation bounds AUTHOR: Michael Hall ADDRESS: Theoretical Physics, IAS, Australian National University, Canberra, ACT 0200, Australia E-MAIL: michael.hall@anu.edu.au STATUS: To appear (in PRA) ABSTRACT: This paper is primarily concerned with the development and application of quantum bounds on mutual information, although some of the methods developed can be applied to any figure of merit indicating degree of correlation, such as coincidence rate. Three basic techniques for obtaining bounds are described: mappings between joint-measurement and communication correlation contexts; a duality relation for quantum ensembles and quantum measurements; and an information exclusion principle. New results include a proof of Holevo's communication bound from a joint-measurement inequality; lower bounds for mutual information under ensemble and measurement constraints; information exclusion relations for measurements described by probability-operator-measures (POMs); a proof that Glauber coherent states are optimal signal states for quantum communication based on (noisy) optical heterodyne detection; and an information inequality for quantum eavesdropping. Relations between the three techniques are used to further obtain new upper bounds for mutual information, and to extend the information exclusion principle to a joint-measurement context. ______________________________________________________________________________ TITLE: Sub-shot noise laser Doppler anemometry with amplitude-squeezed light AUTHORS: Yong-qing Li (1), Peter Lynam (2), Min Xiao (3), and Paul J Edwards (1) ADDRESS: 1. Advanced Telecomunication Research Centre, Faculty of Information Sciences and Engineering, University of Canberra, P.O. Box 1, Belconnen, ACT 2616, Australia; 2. Department of Physics, University College, University of NSW, ADFA, ACT 2600, Australia; 3. Department of Physics, University of Arkansas, Fayetteville, AR 72701, USA. EMAIL: Liy@ise.canberra.edu.au STATUS: submitted to Physical Review Letters ABSTRACT: Amplitude-squeezed light from a quantum-well semiconductor laser with weak optical feedback from a highly dispersive grating is employed for laser Doppler anemometry. Up to 2 dB noise reduction below the shot noise level is observed with a feedback factor of 1.5E-4. Enhanced sensitivity is demonstrated in the Doppler measurement of a gas flow velocity with an improvement in the signal to noise ratio of 1.0 dB above the shot noise limit. ______________________________________________________________________________ 2. CONFERENCES / WORKSHOPS PRELIMINARY ANNOUNCEMENT and CALL FOR PAPERS: THE 11th CONFERENCE OF AUSTRALIAN OPTICAL SOCIETY THE UNIVERSITY OF ADELAIDE, 10 - 12 DEC. 1997 The eleventh conference of The Australian Optical Society will be hosted by the Department of Physics and Mathematical Physics at The University of Adelaide in December 1997. The meeting will concentrate on all aspects of optics, lasers, and applications in Australia with contributions invited from all academic institutions, government laboratories and industry. There will also be a number of invited plenary speakers from overseas. The meeting of the OAS will be immediately preceded by a workshop in Quantum Coherence and Information Processing (8th and/or 9th Dec). Details of the meetings will be appearing in forthcoming issues, and a web page will be established for registration. This will be a great meeting, and Adelaide is at its best in December! If you have suggestions for improvements in the form of topics, distinguished invited speakers, exhibitions, sponsors etc., please forward to: Prof. Jesper Munch, The University of Adelaide, South Australia 5005, Fax. 08 232 6541, email: jmunch@physics.adelaide.edu.au _______________________________________________________________________________ WORKSHOP ON QUANTUM COHERENCE AND INFORMATION PROCESSING ADELAIDE DECEMBER 1997 Dear Colleague, in December 1997 it is planned to hold a workshop in Adelaide on the subject of Quantum Coherence and Information Processing. It will be held in conjunction with the Australian Optical Society meeting (also in Adelaide). The workshop will be held in the day, or two days, preceeding the Optical Society meeting; i.e. Monday 8th and/or Tuesday 9th of December. (The AOS meeting will run Wednesday, Thursday and Friday of the same week.) The workshop is being organised in conjunction with the AOS meeting because much of the experimental progress in the field is based on quantum optical techniques. Nevertheless we hope there will be a broad range of participants, including those who have little interest in the AOS meeting. There will be at least one invited speaker from overseas and one or two local invited speakers, plus contributed talks. The purpose of this flyer is to gauge the level of likely participation so that we can make decisions about (1) whether the workshop will last one or two days . (2) where (exactly!) to hold it. (3) how many speakers to invite. Please indicate by return email (to mwh@physics.adelaide.edu.au) the likelihood of your participation. Suggestions as to the range of topics to be included will also be entertained. The "WE" referred to above is the organising committee comprising Murray Hamilton (U of Adelaide) Gerard Milburn (U of Queensland) Ian Fuss (Defence Science and Technology Org.) Murray Hamilton Department of Physics and Mathematical Physics University of Adelaide Adelaide SA 5005 Australia ****************************************************************************** 3. WANTED TO BUY Anyone knowing the whereabouts of an amplifier plug-in for a Tektronix 7000 series 'scope which might be for sale please contact the editor. We are interested in a dual channel plug-in with 1MegOhm input impedance and bandwidth around 100MHz ****************************************************************************** 4. SITUATIONS VACANT Research Assistant/Associate(Temporary) ARC/DEET Squeezed Light Applications Project A temporary vacancy is available at the University of Canberra for 6 month/one year to continue work on laser diode based photon number squeezed light applications. The joint UC/ADFA Quantum Electronics group has developed an external cavity "quiet" light system which can be operated at room temperature or at liquid nitrogen temperature. This short term position would suit a recent PhD or good Honours graduate with an experimental laser physics background. Experience essential. Terms negotiable. Position available immediately. Contact Paul Edwards: paule@ise.canberra.edu au *************************************************************************** Murray Hamilton Department of Physics and Mathematical Physics University of Adelaide Adelaide SA 5005 Sth Australia Ph + 61 8 8303 5322 fax + 61 8 8232 6541 email mwh@physics.adelaide.edu.au