************************************ * QUANTUM OPTICS AND ATOM OPTICS * * IN AUSTRALASIA * * * * * * * * MONTHLY NEWSLETTER * * VOL XI, NO 3 * * * CONTENTS: * March 2003 * * * 0. EDITORIAL NOTE * ISSN 1325-6467 * Edited by: 1. ABSTRACTS * * Alexei Gilchrist 2. VACANCIES * \ | / * Physics, University of Queensland, 3. BUY/SELL * \__|__/ * QLD 4072, Australia. 4. MISC NEWS * | * email: alexei@physics.uq.edu.au 5. CONFERENCES * | * phone: +61 7 3365 2422 * | * fax: +61 7 3365 1242 Available on WWW at: * * http://www.physics.uq.edu.au/qonews =============================================================================== 0. EDITORIAL NOTE =============================================================================== Sorry about the late mailout, cheers, Alexei =============================================================================== 1. ABSTRACTS =============================================================================== Entanglement in the presence of superselection rules Stephen D. Bartlett, H. M. Wiseman quant-ph/0303140 We quantify bipartite entanglement in the presence of general superselection rules. These rules limit the allowed operations in a bipartite setting and thus place powerful constraints on quantum information processing (QIP). We show that QIP in liquid NMR is subject to the superselection rule associated with the symmetric group (the group of permutations of molecules), and prove that even if each molecule consists of two qubits described by a pure Bell state, the entanglement per molecule in the presence of this superselection rule goes to zero for a large number of molecules. ---------------------------------------------------------------------- Directly Observing Momentum Transfer in Twin-Slit "Which-Way" Experiments H. M. Wiseman quant-ph/0303139 Is the destruction of interference by a which-way measurement due to a random momentum transfer $\wp\agt\hbar/s$, with $s$ the slit separation? The weak-valued probability distribution $P_{\rm wv}(\wp)$, which is {\em directly observable}, provides a subtle answer. $P_{\rm wv}(\wp)$ cannot have support on the interval $[-\hbar/s,\hbar/s]$. Nevertheless, its moments can be identically zero. ---------------------------------------------------------------------- Optical coherence and teleportation: Why a laser is a clock, not a quantum channel Howard M. Wiseman quant-ph/0303116 It has been argued [T. Rudolph and B.C. Sanders, Phys. Rev. Lett. {\bf 87}, 077903 (2001)] that continuous-variable quantum teleportation at optical frequencies has not been achieved because the source used (a laser) was not `truly coherent'. Van Enk, and Fuchs [Phys. Rev. Lett, {\bf 88}, 027902 (2002)], while arguing against Rudolph and Sanders, also accept that an `absolute phase' is achievable, even if it has not been achieved yet. I will argue to the contrary that `true coherence' or `absolute phase' is always illusory, as the concept of absolute time on a scale beyond direct human experience is meaningless. All we can ever do is to use an agreed time standard. In this context, a laser beam is fundamentally as good a `clock' as any other. I explain in detail why this claim is true, and defend my argument against various objections. In the process I discuss super-selection rules, quantum channels, and the ultimate limits to the performance of a laser as a clock. For this last topic I use some earlier work by myself [Phys. Rev. A {\bf 60}, 4083 (1999)] and Berry and myself [Phys. Rev. A {\bf 65}, 043803 (2002)] to show that a Heisenberg-limited laser with a mean photon number $\mu$ can synchronize $M$ independent clocks each with a mean-square error of $\sqrt{M}/4\mu$ radians$^2$. ---------------------------------------------------------------------- Retrodictive states and two-photon quantum imaging E.-K. Tan, John Jeffers, Stephen M. Barnett, David T. Pegg quant-ph/0303099 We use retrodictive quantum theory to analyse two-photon quantum imaging systems. The formalism is particularly suitable for calculating conditional probability distributions. ---------------------------------------------------------------------- On the practicality of time-optimal two-qubit Hamiltonian simulation Henry L. Haselgrove, Michael A. Nielsen, Tobias J. Osborne quant-ph/0303070 What is the time-optimal way of using a set of control Hamiltonians to obtain a desired interaction? Vidal, Hammerer and Cirac [Phys. Rev. Lett. 88 (2002) 237902] have obtained a set of powerful results characterizing the time-optimal simulation of a two-qubit quantum gate using a fixed interaction Hamiltonian and fast local control over the individual qubits. How practically useful are these results? We prove that there are two-qubit Hamiltonians such that time-optimal simulation requires infinitely many steps of evolution, each infinitesimally small, and thus is physically impractical. A procedure is given to determine which two-qubit Hamiltonians have this property, and we show that almost all Hamiltonians do. Finally, we determine some bounds on the penalty that must be paid in the simulation time if the number of steps is fixed at a finite number, and show that the cost in simulation time is not too great. ---------------------------------------------------------------------- Testing integrability with a single bit of quantum information David Poulin, Raymond Laflamme, G.J. Milburn, Juan Pablo Paz quant-ph/0303042 We show that deterministic quantum computing with a single bit (DQC1) can determine whether the classical limit of a quantum system is chaotic or integrable using only $O(\sqrt N)$ physical resources, where $N$ is the dimension of the Hilbert space of the system under study. This is a square root improvement over all known classical procedures. Our study relies strictly on the random matrix conjecture. We also present numerical results for the nonlinear kicked top. ---------------------------------------------------------------------- Ancilla-assisted quantum process tomography J. B. Altepeter, D. Branning, E. Jeffrey, T. C. Wei, P. G. Kwiat, R. T. Thew, J. L. O'Brien, M. A. Nielsen, A. G. White quant-ph/0303038 Complete and precise characterization of a quantum dynamical process can be achieved via the method of quantum process tomography. Using a source of correlated photons, we have implemented several methods investigating a wide range of processes, e.g., unitary, decohering, and polarizing. One of these methods, ancilla-assisted process tomography (AAPT), makes use of an additional ``ancilla system,'' and we have theoretically determined the conditions when AAPT is possible. All prior schemes for AAPT make use of entangled states. Our results show that, surprisingly, entanglement is not required for AAPT, and we present process tomography data obtained using an input state that has no entanglement. However, the use of entanglement yields superior results. ---------------------------------------------------------------------- Quantum states far from the energy eigenstates of any local Hamiltonian Henry L. Haselgrove, Michael A. Nielsen, Tobias J. Osborne quant-ph/0303022 What quantum states are possible energy eigenstates of a many-body Hamiltonian? Suppose the Hamiltonian is non-trivial, i.e., not a multiple of the identity, and L-local, in the sense of containing interaction terms involving at most L bodies, for some fixed L. We construct quantum states \psi which are ``far away'' from all the eigenstates E of any non-trivial L-local Hamiltonian, in the sense that |\psi-E| is greater than some constant lower bound, independent of the form of the Hamiltonian. ---------------------------------------------------------------------- Teleportation with a uniformly accelerated partner Paul M. Alsing, G.J. Milburn quant-ph/0302179 In this work, we give a description of the process of teleportation between Alice in an inertial frame, and Rob who is in uniform acceleration with respect to Alice. The fidelity of the teleportation is reduced due to Unruh radiation in Rob's frame. In so far as teleportation is a measure of entanglement, our results suggest that quantum entanglement is degraded in non inertial frames. ---------------------------------------------------------------------- Requirement for quantum computation Stephen D. Bartlett, Barry C. Sanders quant-ph/0302125 We identify "proper quantum computation" with computational processes that cannot be efficiently simulated on a classical computer. For optical quantum computation, we establish "no-go" theorems for classes of quantum optical experiments that cannot yield proper quantum computation, and we identify requirements for optical proper quantum computation that correspond to violations of assumptions underpinning the no-go theorems. ---------------------------------------------------------------------- Classical and quantum communication without a shared reference frame Stephen D. Bartlett, Terry Rudolph, R. W. Spekkens quant-ph/0302111 We show that communication without a shared reference frame is possible using entangled states. We prove that the amount of classical information that can be communicated without a shared reference frame asymptotically approaches one classical bit per qubit sent, and that the number of encoded qubits which can be communicated per transmitted qubit also asymptotically approaches unity. We present an optical scheme to communicate classical bits without a shared reference frame using entangled photon pairs and linear optical Bell state measurements. =============================================================================== 2. VACANCIES =============================================================================== ADVERTISEMENT FOR CANADA RESEARCH CHAIR AT THE UNIVERSITY OF CALGARY http://careers.peopleclick.com/jobposts/Client40_UofC/BU1/External/32-1479.htm Job ID #:1504 Title:Department of Physics and Astronomy The Department of Physics and Astronomy at the University of Calgary invites applications from outstanding candidates in experimental atomic, molecular, and optical (AMO) physics for nomination to a Tier II Canada Research Chair (CRC) in Experimental Quantum Information Science. The Canada Research Chairs Programme has been established by the Canadian government to enable Canadian universities to foster research excellence and enhance their role as world class centres of research. Further information on the CRC programme may be found at http://www.chairs.gc.ca. This assistant professorship is part of the University's expansion in quantum information science, which includes the disciplines of experimental and theoretical physics in addition to computer science. As of September 2003, the Department will be the home of a new research group in quantum information science, supported by the Alberta Informatics Circle of Research Excellence (iCORE) program. The new faculty member will have the opportunity to interact closely with dynamic research groups in the Department of Computer Science currently investigating fundamental issues in quantum algorithms, complexity theory, and cryptography, and with current members of the AMO group in the Department of Physics and Astronomy, whose current activities include ion cooling and trapping, high resolution spectroscopy, and degenerate dilute atomic gases. Prospective candidates are encouraged to visit www.cpsc.ucalgary.ca/Research/quantum. The successful candidate must have a Ph.D. and postdoctoral experience or equivalent in experimental physics, an excellent track record in experimental physics research, an ability to establish and maintain an outstanding research program in quantum information science, and a strong commitment to teaching excellence. Applications with curriculum vitae (including a full list of publications, statements of research, and teaching goals) and four letters of reference should be sent to: Chair, Search Committee; Experimental Quantum Information Science; Department of Physics and Astronomy; University of Calgary, Calgary, AB, Canada T2N 1N4; E-mail: jcarr@ucalgary.ca; Telephone: (403) 220-3293; Fax: (403) 282-9154. The deadline for applications is May 15, 2003. Nomination to the CRC Program will occur in September 2003, and the anticipated start date is July 1, 2004. The University of Calgary respects, appreciates and encourages diversity. PLEASE DO NOT APPLY ONLINE, AS WE ARE NOT ACCEPTING ONLINE APPLICATIONS FOR TEACHING OR RESEARCH POSITIONS AT THIS TIME. THANK YOU FOR YOUR COOPERATION. ------------------------------------------------------------------- Postdoctoral Positions in Quantum Information Science The University of Calgary invites applications for several postdoctoral research positions in the area of quantum information science, available from September 2003. Researchers interested in all areas of quantum computation and quantum information will be considered. These postdoctoral positions are part of the University of Calgary's expansion in quantum information science, which is a collaboration between the departments of Computer Science and Physics & Astronomy. Current members include Richard Cleve, Peter Hoyer, and John Watrous in the Department of Computer Science, and David Feder and Barry Sanders (as of July 2003) in the Department of Physics & Astronomy. In addition the group will include a Canada Research Chair in Experimental Quantum Information Science to begin in 2004. Applicants should send a curriculum vitae (including a full list of publications and a research statement) and the names and contact details for three references by email to: qis@cpsc.ucalgary.ca. ------------------------------------------------------------------- POSTDOCTORAL POSITION IN COLD QUANTUM GASES Department of Physics, University of Toronto http://physics.utoronto.ca/~jht/postdoc.html Applications are invited for a postdoctoral position in experimental AMO physics. Candidates could start as early as September 2003, but the position will remain open until an appropriate candidate is found. The holder of this position will work on research in ultra-cold quantum gases in the Thywissen group, one of the labs in the quantum optics and condensed matter cluster in the Department of Physics at the University of Toronto. This cluster places cold atom research in the context of quantum optics and condensed matter physics, and also benefits from proximity to Photonics Research Ontario (PRO), an Ontario Center of Excellence. The research topic, ultra-cold quantum gases, is one of the most exciting topics in atomic, molecular, and optical (AMO) physics research. Experiments combine methods of laser cooling with magnetic trapping and evaporative cooling to create quantum degenerate gases of bosons and fermions. The successful candidate would work on an experiment that uses microfabricated trapping elements to create powerful traps for mesoscopic atomic ensembles. Note that although knowledge of AMO techniques and theory would be useful, candidates with a successful experimental research background in related fields are welcome to apply. The postdoctoral appointment is initially for one year and may be renewed. The salary is competitive, and benefits include the Ontario Health Insurance Plan, free of charge. Health care is also available to dependents for a small fee. Please send CV, publication list, and the names of at least two references to Joseph H Thywissen jht@physics.utoronto.ca or to Joseph H Thywissen Department of Physics 60 St George Street University of Toronto Toronto, Ontario, Canada M5S 1A7 The University of Toronto is strongly committed to diversity within its community and especially welcomes applications from visible minority group members, women, Aboriginal persons, persons with disabilities, members of sexual minority groups and others who may contribute to further diversification of ideas. All qualified candidates are encouraged to apply. =============================================================================== 5. CONFERENCES / WORKSHOPS =============================================================================== Simons Conference on Quantum and Reversible Computation May 28-31, 2003. deadline for application is April 1, 2003 Stony Brook http://insti.physics.sunysb.edu/itp/conf/simons-qcomputation.html The goal of this conference is to generate interaction between mathematicians, computer scientists and physicists trying to build quantum computers. We will stimulate this interaction with lectures on recent developments by world-experts. We shall have lectures on quantum algorithms, quantum information theory, cryptography, entanglement and quantum error correcting codes [ we shall have a special lecture on modular functors]. We shall organize lectures on recent developments in Fractional Quantum Hall Effect, Josephson-junction, QED cavities, ion trapes and quantum optical systems. The conference will also cover reversible information processing, which is of interest in classical as well as in quantum computing. The reversible nature of the quantum evolution of isolated systems makes logical reversibility on the classical level a prerequisite for any realization of a quantum computer. Reversible computing does not generate the heat associated with information erasure, and is therefore of interest in reducing the heat produced by classical computers. ------------------------------------------------------------------- Fluctuations and Noise 2003 1-4 June 2003 Abstract Due: 25 November 2002 Santa Fe, New Mexico USA http://spie.org/Conferences/Calls/03/fn/ Containing six parallel conferences: * Fluctuations and Noise in Biological, Biophysical, and Biomedical Systems * Fluctuations and Noise in Photonics and Quantum Optics * Noise as a Tool for Studying Materials * Noise in Devices and Circuits * Noise in Complex Systems and Stochastic Dynamics * Noise and Information in Nano-electronics, Sensors, and Standards ------------------------------------------------------------------- 8th International Conference on Squeezed States and Uncertainty Relations 9-13 June, 2003 Puebla, Mexico http://www-optica.inaoep.mx/ICSSUR/8th.html The program of the Conference will reflect the continuing importance of fundamental quantum physics and the increasing importance of applications in the domain of quantum optics. Contributed experimental and theoretical papers in all of these topics are solicited: o Squeezed states and uncertainty relations o Quantum-state generation and characterization o Phase space and group representations in quantum physics o Quantum transforms in signal analysis and quantum physics o Quantum interference and entanglement o Quantum-like and mesoscopic systems o Foundations of quantum mechanics and quantum optics o Trapped atoms and degenerate gases o Quantum chaos and quantum control o Quantum information and communication o Quantum computing ------------------------------------------------------------------- Benasque Center for Science - Quantum Information 22nd June - 11th July 2003 Deadline for applications is March 15. Barcelona, Spain http://sophia.ecm.ub.es/2003qi/2003qi.htm A three-week Benassque session will be devoted to recent progress in Quantum Information and Communication. Special topics that will be covered during the meeting are: * Theory of Quantum Information,Entanglement, Quantum Algorithms,... QCD * Experiments in Quantum Information, Trapped ions, photons, NMR, Superconducting currents, quantum dots, ------------------------------------------------------------------- Les Houches Summer School on 'Quantum entanglement and information processing' 30 June - 25 July, 2003. Registration deadline: March 7, 2003 Les Houches, France. http://www-houches.ujf-grenoble.fr/index-en.html The recent discovery that the laws of quantum physics could be used for efficient information processing or transmission led to a considerable upsurge of interest in developing a deeper understanding of quantum mechanics, and in fabricating genuine quantum processors. This new field gathers around common objectives various communities, such as theoretical physics, quantum optics or solid state physics. On the theoretical side, the major advances concern quantum algorithms and quantum error correction codes. On the experimental side, significant advances have been realized in quantum optics, solid state physics and nuclear magnetic resonance. In particular, quantum logic gates have been demonstrated, and small-size quantum algorithms have been operated. This school aims to provide a comprehensive overview of the theoretical and experimental aspects of quantum entanglement and information processing. It is opened to young researchers interested in learning the essentials of this new field. Introductory lectures will provide them with a common background, while more specialized lectures and seminars will give an up to date panorama. ------------------------------------------------------------------- ICOLS 03: 16th International Conference on Laser Spectroscopy 13-18 July 2003 Preregistration: 13 December 2002 Earlybird registration and abstracts: 28 April 2003 Palm Cove, AUSTRALIA http://www.swin.edu.au/rescentres/soll/icols03/icols.html Following the tradition of ICOLS conferences, the program will consist of single sessions of invited talks and posters covering the latest developments in Laser Spectroscopy and related topics. Scheduling will allow significant time for informal discussions. The number of participants will be limited to about 250-300. ------------------------------------------------------------------- 4th European QIPC Workshop 13th - 18th July 2003 Submission deadline: 04 April 2003 Oxford, UK http://www.quiprocone.org/4th_Keble.htm The purpose of the workshop is to promote interaction across the broad subject area of QIPC and follows previous meetings in Potsdam, ISI Torino and Trinity College Dublin. ------------------------------------------------------------------- 48th SPIE Meeting: Quantum Communications and Quantum Imaging (AM112) 3-8 August 2003 Abstract Due: 6 January 2003 Manuscript Due: 7 July 2003 http://spie.org/Conferences/Calls/03/am/conferences/index.cfm?fuseaction=AM112 Quantum communications and quantum imaging are emerging technologies that promise great benefits as well as great challenges. The objective of this conference is to provide a forum for researchers and system developers in both fields and encourage technology exchange between the quantum communication and quantum imaging communities. ------------------------------------------------------------------- IWQDQC: The 2nd International Workshop on Quantum Dots for Quantum Computing 7-9 August, 2003 Deadline for abstracts: 15 March 2003 Early registration: 1 July, 2003 University of Notre Dame, Indiana, USA http://www.nd.edu/%7Eiwqdqc/index.html The workshop is intended to be an international forum for discussions on the current trends and future directions of research in quantum dots and solid-state implementations for quantum computing. ------------------------------------------------------------------- Quantum Optics - EuroConference on Cavity QED and Quantum Fluctuations: From Fundamental Concepts to Nano-Technology 27 September - 02 October 2003 Applications by 26 May 2003 Granada, Spain http://www.esf.org/euresco/03/pc03005 Quantum Optics is a very active and fast evolving field in physics with at its core the understanding and control of quantum systems. The objective of the Quantum Optics Euroconferences is to bring together the leading groups in the field with the emphasis on combining knowledge and technology of different subfields and identifying new promising directions. The 2003 Quantum Optics conference will focus on cavity quantum electrodynamics and quantum fluctuations, covering a broad range of topics from fundamental concepts of quantum optics to technological developments. Sessions will be devoted to cavity QED, Casimir forces and their impact in nanostructures, quantum information and decoherence phenomena, coherent atomic sources and BEC in atom chips and wave guides. In close connection with these topics a session will address the new emerging field of nano-optics. ------------------------------------------------------------------- Solid State Quantum Information Processing 15-18 December 2003 Registration: October 29, 2003 Amsterdam Renaissance Hotel, The Netherlands http://ssqip.tudelft.nl This conference aims at (1) reviewing the progress in quantum information processing using devices built in the solid state, (2) reporting the most recent results, and (3) identifying promises and challenges in this field.