Subject: Date: Fri, 9 May 1997 13:24:49 +0930 (CST) From: Murray Hamilton To: mwh@physics.adelaide.edu.au ************************************ * QUANTUM OPTICS AND ATOM OPTICS * * IN AUSTRALASIA * * * * * * * * MONTHLY NEWSLETTER * * VOL V, NO 5 * * * * May 1997 * * * * ISSN 1325-6467 * * * Edited by: Murray Hamilton * \ | / * Physics, University of Adelaide, * \__|__/ * SA 5005, Australia. * | * email: mwh@physics.adelaide.edu.au Available on WWW at: * | * phone: +61 8 8303 5322 http://www.anu.edu.au * | * fax: +61 8 8232 6541 /Physics/newsletter * * ___________________ ------------------------------------------------------------------------------ CONTENTS 0. PROBLEMS 1. ABSTRACTS 2. CONFERENCE ANNOUNCEMENTS 3. WANTED TO BUY/SELL 4. SITUATIONS VACANT 5. MISC NEWS (real news if you like!) ______________________________________________________________________________ 0. DISTRIBUTION PROBLEMS This is a second try as the first appeared to get lost somewhere in cyberspace. If the first one made it then it's not my mailserver going berserk (which has happened) but just getting a wee bit confused. ___________________ 1. ABSTRACTS Title: Sub-shot noise laser Doppler anemometry with amplitude-squeezed light. Authors: Yong-qing Li (1), Peter Lynam (2), Min Xiao (3), and Paul Edwards (1). Address: (1) Advanced Telecommunications Research Centre, Faculty of Information Sciences and Engineering, University of Canberra, PO Box 1, Belconnen ACT 2616; (2) Department of Physics, University College, UNSW ADFA, ACT 2600; (3) Department of Physics, University of Arkansas, Fayetteville AR 72701. Abstract: stract: 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 1.5 E -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. Physical Review Letters 78, 16, pp3105-3108, April 21 1997. _________________________________________________________________________ DRUMMOND, P. D., HE, H. and KHERUNTSYAN, K. V., Optical `mesons' in parametric waveguides. To appear, `Proceedings of conference on Quantum Optics and Laser physics, Hong Kong' (Springer 1997). Abstract:Optical `mesons' (di-photon quantum solitons) are shown to exist in parametric waveguides. These provide an ideal quantum soliton environment, because of more realistic formation lengths and binding energies than chi(3) quantum solitons. WERNER, M.J. and DRUMMOND, P.D. University of Queensland Robust algorithms for solving stochastic partial differential equations. To appear, Journal of Computational Physics. Abstract:A robust semi-implicit computer algorithm for the numerical solution of coupled stochastic parabolic partial differential equations is described. This can be used for calculating correlation functions of systems of interacting stochastic fields. Such field equations can arise in the description of Hamiltonian and open systems in the physics of nonlinear processes, and may include multiplicative noise sources. The algorithm can be used for studying the properties of nonlinear quantum or classical field theories. The general approach is outlined and applied to a specific example, namely thequantum statistical fluctuations of ultra-short pulses in $\chi^{(2)}$ parametric waveguides. This example uses a non-diagonal coherent state representation, and correctly predicts the sub-shot noise level spectral fluctuations observed in homodyne detection measurements. It is expected the methods used will be applicable for higher-order correlation functions and other physical problems as well. A stochastic differencing technique for reducing sampling errors is also introduced. This involves solving nonlinear stochastic parabolic PDE's in combination with a reference process, which uses the Wigner representation in the example presented here. A computer implementation on MIMD parallel architectures is discussed. GILCHRIST, A., GARDINER, C.W. and DRUMMOND, P.D., The Positive P-representation: application and validity. To appear, Phys. Rev. A. Abstract: The positive P-representation is a very successful tool in quantum optics. However, the usual assumption of negligible boundary terms in the time-evolution equations is not always valid. We explore the range of validity of the time-evolution equations both analytically and by numerical investigation of a number of specific examples. We present practical ways of verifying the validity of the use of the positive P-representation and find that the standard time-evolution equation can become invalid when nonlinear terms (at unit photon number) are large relative to the damping rate. This is very much larger than is normally the case in nonlinear optics, except possibly near to resonances. We are able to show that when the positive P-representation is invalid, the boundary terms, normally neglected in an integration by parts, become non-negligible. When numerical simulations are carried out using the positive P-representation, specific checks given in this paper should be carried out to verify the compactness of the distribution. In conclusion, we find that (apart from special cases) this technique of quantum time-evolution is typically asymptotically valid in the limit of small nonlinearity, rather than exact. DUDLEY, J. M., BARRY, L. P., BOLLOND, P. G., HARVEY, J. D. LEONHARDT, R. and DRUMMOND, P. D., University of Auckland "Direct measurement of pulse distortion near the zero-dispersion wavelength in an optical fiber using frequency resolved optical gating." To appear, Optics Letters. Abstract:The technique of frequency-resolved optical gating (FROG) is used to characterise the intensity and phase of picosecond pulses after propagation through 700m of fiber at close to the zero dispersion wavelength. Using the FROG technique, we directly measure the severe temporal distortion resulting from the interplay between self-phase modulation and higher order dispersion in this regime. The measured intensity and phase of the pulses after propagation are found to be in good agreement with the predictions of numerical simulations using the nonlinear Schrodinger equation. _____________________________________________________________________________ title: Adaptive single-shot phase measurements: a semiclassical approach authors: H.M.~Wiseman and R.B.~Killip address for correspondence: Department of Physics, The University of Queensland, St.~Lucia 4072, Australia abstract: The standard single-shot estimate for the phase of a single-mode pulse of light is the argument of the complex amplitude of the field. This complex amplitude can be measured by heterodyne detection, in which the local oscillator is detuned from the system so that all quadratures are sampled equally. Because different quadratures do not commute, such a measurement introduces noise into the phase estimate, with a variance scaling as $N^{-1}$ where $N$ is the maximum photon number. This represents the shot-noise-limit or standard-quantum-limit (SQL). Recently, one of us [H.M. Wiseman, Phys. Rev. Lett. {\bf 75}, 4587 (1995)] proposed a way to improve upon this: a real-time feedback loop can control the local oscillator phase to be equal to the estimated system phase plus $\pi/2$, so that the phase quadrature of the system is measured preferentially. The phase estimate used in the feedback loop at time $t$ is a functional of the photocurrent from time $0$ up to time $t$ in the single-shot measurement. In this paper we consider a very simple feedback scheme involving only linear electronic elements. Approaching the problem from semiclassical detection theory, we obtain analytical results for asymptotically large photon numbers. Specifically, we are able to show that the noise introduced by the measurement has a variance scaling as $N^{-3/2}$. This is much less than the SQL variance, but still much greater than the minimum intrinsic phase variance which scales as $N^{-2}$. We briefly discuss the effect of detector inefficiencies and delays in the feedback loop. status: to be published in Phys. Rev. A. _____________________________________________________________________________ Paper: physics/9703032 Title: Jones-matrix Formalism as a Representation of the Lorentz Group Authors: D. Han, Y. S. Kim, and Marilyn E. Noz Comments: RevTeX, 27 pages, no figures, to be published in J. Opt. Soc. Am. A Subj-class: Optics \\ It is shown that the two-by-two Jones-matrix formalism for polarization optics is a six-parameter two-by-two representation of the Lorentz group. The attenuation and phase-shift filters are represented respectively by the three-parameter rotation subgroup and the three-parameter Lorentz group for two spatial and one time dimensions. It is noted that the Lorentz group has another three-parameter subgroup which is like the two-dimensional Euclidean group. Possible optical filters having this Euclidean symmetry are discussed in detail. It is shown also that the Jones-matrix formalism can be extended to some of the non-orthogonal polarization coordinate systems within the framework of the Lorentz-group representation. _____________________________________________________________________________ ******************************************************************************* 2. CONFERENCES / WORKSHOPS --------------------------- _______________________________________________________________________________ THE 11th CONFERENCE OF AUSTRALIAN OPTICAL SOCIETY THE UNIVERSITY OF ADELAIDE, 10 - 12 DEC. 1997 This now has a web page. - go to http://bragg.physics.adelaide.edu.au/~mwh/aosmeet/aosmeet.html _______________________________________________________________________________ Workshop on QUANTUM COHERENCE AND INFORMATION PROCESSING UNIVERSITY OF ADELAIDE 8,9 DECEMBER 1997 Webpage: http://bragg.physics.adelaide.edu.au/~mwh/qiproc/qiproc.html _________________________________________________________________________ INTERNATIONAL CONFERENCE QUANTUM OPTICS IV JASZOWIEC, POLAND JUNE 17-24, 1997 Circular and registration form are available on the WWW pages at http://info.ifpan.edu.pl/conferences/qo4.html _________________________________________________________________________ IV Workshop Optics and Interferometry with Atoms 21st - 23rd July 1997 St. John's College, Oxford, England. The application form and further details can also be found at our www site: http://eve.physics.ox.ac.uk/Confer/atopt/home.html _________________________________________________________________________ For other interesting conferences, send an e-mail to with CONFMENU on your Subject line, or web . ****************************************************************************** 3. ****************************************************************************** 4. SITUATIONS VACANT None this month - really grim! ****************************************************************************** 5. MISC NEWS ****************************************************************************** The end. 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