************************************ * QUANTUM OPTICS AND ATOM OPTICS * * IN AUSTRALASIA * * * * * * * * MONTHLY NEWSLETTER * * VOL XI, NO 9 * * * CONTENTS: * September 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 =============================================================================== Please note the impending deadline on the ANU postdoc. Alexei =============================================================================== 1. ABSTRACTS =============================================================================== On improving single photon sources via linear optics and photodetection Dominic W. Berry, Stefan Scheel, Barry C. Sanders, Peter L. Knight quant-ph/0309140 In practice, single photons are generated as a mixture of vacuum with a single photon with weights 1-p and p, respectively; here we are concerned with increasing p by directing multiple copies of the single photon-vacuum mixture into a linear optic device and applying photodetection on some outputs to conditionally prepare single photon states with larger p. We prove that it is impossible, under certain conditions, to increase p via linear optics and conditional preparation based on photodetection, and we also establish a class of photodetection events for which p can be improved. In addition we prove that it is not possible to obtain perfect (p=1) single photon states via this method from imperfect (p<1) inputs. ---------------------------------------------------------------------- Ferreting out the Fluffy Bunnies: Entanglement constrained by Generalized superselection rules Howard M. Wiseman, Stephen D. Bartlett, John A. Vaccaro quant-ph/0309046 Entanglement is a resource central to quantum information (QI). In particular, entanglement shared between two distant parties allows them to do certain tasks that would otherwise be impossible. In this context, we study the effect on the available entanglement of physical restrictions on the local operations that can be performed by the two parties. We enforce these physical restrictions by generalized superselection rules (SSRs), which we define to be associated with a given group of physical transformations. Specifically the generalized SSR is that the local operations must be covariant with respect to that group. Then we operationally define the entanglement constrained by a SSR, and show that it may be far below that expected on the basis of a naive (or ``fluffy bunny'') calculation. We consider two examples. The first is a particle number SSR. Using this we show that for a two-mode BEC (with Alice owning mode $A$ and Bob mode $B$), the useful entanglement shared by Alice and Bob is identically zero. The second, a SSR associated with the symmetric group, is applicable to ensemble QI processing such as in liquid-NMR. We prove that even for an ensemble comprising many pairs of qubits, with each pair described by a pure Bell state, the entanglement per pair constrained by this SSR goes to zero for a large ensemble. ---------------------------------------------------------------------- A characterization of continuous variable entanglement W. P. Bowen, R. Schnabel, P. K. Lam, T. C. Ralph quant-ph/0309013 We present an experimental analysis of quadrature entanglement produced from a pair of amplitude squeezed beams. The correlation matrix of the state is characterized within a set of reasonable assumptions, and the strength of the entanglement is gauged using measures of the degree of inseparability and the degree of EPR paradox. We introduce controlled decoherence in the form of optical loss to the entangled state, and demonstrate qualitative differences in the response of the degrees of inseparability and EPR paradox to this loss. The entanglement is represented on a photon number diagram that provides an intuitive and physically relevant description of the state. We calculate efficacy contours for several quantum information protocols on this diagram, and use them to predict the effectiveness of our entanglement in those protocols. ---------------------------------------------------------------------- Quantum entanglement and fixed-point bifurcations Andrew P. Hines, G.J. Milburn, Ross H. McKenzie quant-ph/0308165 How do the classical dynamics of a composite system relate to the entanglement characteristics of the corresponding quantum system? We show that entanglement in nonlinear bipartite systems can be associated with a fixed point bifurcation in the classical description. In a non dissipative system a fixed point corresponds to a quantum stationary state, usually a ground state. Using the example of coupled giant spins we show that, when the fixed point undergoes a supercritical pitchfork bifurcation, the corresponding quantum state achieves a maximum amount of entanglement. By way of contrast, we consider a molecular BEC system that experiences a different kind of bifurcation and does not exhibit the a peak in the entanglement corresponding to the bifurcation parameter. ---------------------------------------------------------------------- Measuring Controlled-NOT and two-qubit gate operation Andrew G. White, Alexei Gilchrist, Geoffrey J. Pryde, Jeremy L. O'Brien, Michael J. Bremner, Nathan K. Langford quant-ph/0308115 Accurate characterisation of two-qubit gates will be critical for any realisation of quantum computation. We discuss a range of measurements aimed at characterising a two-qubit gate, specifically the CNOT gate. These measurements are architecture-independent, and range from simple truth table measurements, to single figure measures such as the fringe visibility, parity, fidelity, and entanglement witnesses, through to whole-state and whole-gate measures achieved respectively via quantum state and process tomography. In doing so, we examine critical differences between classical and quantum gate operation. ---------------------------------------------------------------------- Teleportation of continuous variable polarisation states A. Dolinska, B. C. Buchler, P. K. Lam, T. C. Ralph, W. P. Bowen quant-ph/0308090 This paper discusses methods for the optical teleportation of continuous variable polarisation states. We show that using two pairs of entangled beams, generated using four squeezed beams, perfect teleportation of optical polarisation states can be performed. Restricting ourselves to 3 squeezed beams, we demonstrate that polarisation state teleportation can still exceed the classical limit. The 3-squeezer schemes involve either the use of quantum non-demolition measurement or biased entanglement generated from a single squeezed beam. We analyse the efficacies of these schemes in terms of fidelity, signal transfer coefficients and quantum correlations. ---------------------------------------------------------------------- Entanglement, correlations, and the energy gap in many-body quantum systems Henry L. Haselgrove, Michael A. Nielsen, Tobias J. Osborne quant-ph/0308083 What correlations are present in the ground state of a many-body Hamiltonian? We study the relationship between ground-state correlations, especially entanglement, and the energy gap between the ground and first excited states. We prove several general inequalities which show quantitatively that ground-state correlations between systems not directly coupled by the Hamiltonian necessarily imply a small energy gap. ---------------------------------------------------------------------- Comparison of LOQC C-sign gates with ancilla inefficiency and an improvement to functionality under these conditions A. P. Lund, T. B. Bell, T. C. Ralph quant-ph/0308071 We compare three proposals for non-deterministic C-sign gates implemented using linear optics and conditional measurements with non-ideal ancilla mode production and detection. The simplified KLM gate [Ralph et al, Phys.Rev.A {\bf 65}, 012314 (2001)] appears to be the most resilient under these conditions. We also find that the operation of this gate can be improved by adjusting the beamsplitter ratios to compensate to some extent for the effects of the imperfect ancilla. ---------------------------------------------------------------------- Gaussian quantum operator representation for bosons Joel F. Corney, Peter D. Drummond quant-ph/0308064 We introduce the Gaussian quantum operator representation, using the most general multi-mode Gaussian operator basis. The representation unifies and substantially extends existing phase-space representations of density matrices for Bose systems, and also includes generalized squeezed-state and thermal bases. It enables first-principles dynamical or equilibrium calculations in quantum many-body systems, with quantum uncertainties appearing as dynamical objects. Any quadratic Liouville equation for the density operator results in a purely deterministic time evolution. Any cubic or quartic master equation can be treated using stochastic methods. =============================================================================== 2. VACANCIES =============================================================================== THE AUSTRALIAN NATIONAL UNIVERSITY AUSTRALIAN RESEARCH COUNCIL CENTRE OF EXCELLENCE FOR QUANTUM-ATOM OPTICS Research School of Physical Sciences and Engineering Atomic and Molecular Physics Laboratories POSTDOCTORAL FELLOW LEVEL A Fixed term appointment EXPERIMENTAL ATOMIC AND OPTICAL PHYSICS PSE 1901/03 Closing date: Friday 30th September 2003 Applications are invited for a Postdoctoral Fellowship starting in 2004 for a new experimental program on Bose-Einstein condensation of metastable helium associated with the recently-funded Australian Research Council Centre of Excellence in Quantum-Atom Optics. The program will be located in the Centre node at the Research School of Physical Sciences and Engineering (AMPL, RSPhysSE), ANU Institute of Advanced Studies: Bose-Einstein Condensation with Metastable Helium Based on our long-standing expertise in experimental laser cooling and manipulation of metastable helium (23S) atoms, we will establish a Bose-Einstein Condensation (BEC) experimental facility to enable studies of quantum-atom optical processes with single particle detection capabilities. In particular, we aim to study the evolution of the relative phase of condensates created in multiple potential wells. The experiments will be closely supported by the theory core in the Centre. Applicants should have a PhD in experimental Atomic and Optical Physics (or related areas) and specific experience in one or more of the following areas would be a distinct advantage: Laser cooling and trapping of atoms Metastable helium atom manipulation The position will be available in early 2004 and will be up to 4 years in duration. Starting salary will be A$47,721 and some funds may be available to cover travel and relocation costs. In addition, a generous superannuation scheme operates at the ANU. For further information on the Metastable Helium BEC project see our web page at wwwrsphysse.anu.edu.au/ampl/he_bec or contact Dr. Andrew Truscott on +61 2 6125 3626 and at Andrew.Truscott@anu.edu.au . For information on the Centre and its activities see our web page at www.acqao.org or contact Dr. Ken Baldwin on +61 2 6125 4702 and at Kenneth.Baldwin@anu.edu.au. Contact: Intending applicants must obtain further particulars and selection criteria from Gillian Harman, RSPhysSE, Ph: (+61) 2 6125 5195, Fax: (+61) 2 6125 2966, Email: hr.rsphysse@anu.edu.au ------------------------------------------------------------------- Institut fur Theoretische Physik, Max-Planck Institut fur Optik, Information und Photonik Quantum Cryptography (Quantum Information Theory) Research Location: Erlangen (Germany) Research Topic: Quantum Key Distribution Key words: Design of efficient and practical quantum key distribution protocols. Security evaluations, including quantum error correction techniques. Exploitation of quantum correlations via classical communication protocols. Within an existing DFG project and for a newly established EU funded collaboration we are seeking to fill the following vacant positions: Positions: Postdoc (2 years, extendible for additional 2 years, BAT IIa.) Profile: Experience in quantum information theory, interest in quantum key distribution and quantum optical implementations. Demonstration of independent research is expected. Direction: Coordination and derivation of security evaluations for implementations of state-of-the-art quantum key distribution platforms. Target starting date: January 1st, 2004. PhD-Student (3 years, BAT IIa/2.) Profile: Basic education in quantum information theory, interest in classical information theory and quantum optical implementations. Direction: Development of novel classical communications protocols utilizing quantum correlations. Earliest starting date: October 1st, 2003. Research Group: Emmy-Noether Research Group 'Quantum Information Theory', Institut für Theoretische Physik, University of Erlangen-Nürnberg, Erlangen, Germany. Our group is one of the leading groups in the theory of quantum key distribution with a strong international reputation for the security of practical systems. The group has clear international character. More information about our group under: http://www.optik.uni-erlangen.de/leuchs/qit/Main.html If you are interested in these openings, please contact: Dr. Norbert Lutkenhaus, norbert.luetkenhaus@physik.uni-erlangen.de , +49-9131-852 8375 ------------------------------------------------------------------- Sam Braunstein DEPARTMENT OF COMPUTER SCIENCE Research Associate - Quantum Information Processing Ref: CR0384 DEPARTMENT OF COMPUTER SCIENCE Applications are invited for a two-year EPSRC funded postdoctoral research position for theoretical work directed at the application of quantum computation. You will be expected to have a track record of research in quantum computation, quantum information, quantum optics or related fields. The post is available from 01 December 2003 for a period of up to two years. The salary will be within the range of 18,265 to 20,311 per annum (pay award pending). Informal enquiries should be made to Professor Samuel Braunstein by email (schmuel@cs.york.ac.uk) The closing date for applications will be Thursday 16 October 2003. For further particulars and details of how to apply, please write to the Personnel & Staff Development Office, University of York, Heslington, York YO10 5DD, or email: jobs@york.ac.uk quoting reference number CR0384, or see: (URL: http://www.york.ac.uk/admin/persnl/jobs/) The University of York is committed to diversity and has policies and developmental programmes in place to promote equality of opportunity. It particularly welcomes applications from ethnic minority candidates. ------------------------------------------------------------------- University Lecturer in Materials DEPARTMENT OF MATERIALS in association with Mansfield College The closing date for applications is 17 October 2003. http://www.admin.ox.ac.uk/ps/gp/current/http006.shtml The Department of Materials proposes to appoint a University Lecturer in Materials with effect from 1 January 2004 or as soon as possible thereafter. The successful candidate will be offered a Tutorial Fellowship by Mansfield College, under arrangements described in the further particulars. The combined University and College salary will be according to age on a scale up to £42,900 (as at 1 August 2002, under review). Applicants should have a strong research background in a field related to Quantum Information Processing. The successful candidate will be expected to carry out advanced research and teaching in the Department of Materials, and to give tuition to, and be responsible for organising the tuition of, junior members of Mansfield College reading for degrees in Materials Science. Further particulars, containing details of the application procedure and of the duties and full range of benefits and allowances attached to both the university and college appointments, may be obtained from the departmental website: http://www.materials.ox.ac.uk, or from Professor G.D.W. Smith, FRS, Head of Department, University of Oxford Department of Materials, Parks Road, Oxford OX1 3PH, UK (email: head.department@materials.ox.ac.uk). =============================================================================== 5. CONFERENCES / WORKSHOPS =============================================================================== 304th Heraeus-Seminar "Elementary Quantum Processors" 13th - 15th October 2003 Registration: August 31, 2003 Bad Honnef, Germany http://www.weh304.de/ Concepts for the implementation of elementary quantum processors abound in many areas of physics, including quantum optics, quantum dot physics, spin electronics, superconducting devices, and more. At the Physikzentrum leading researchers will survey the state of art in engineering elementary quantum logic devices. Intense scientific communication about this exciting topic is warranted. ------------------------------------------------------------------- ACOLS 03: The Australasian Conference on Optics, Lasers, and Spectroscopy 1-4 December 2003 Abstracts: 30 September 2003 Registration: 30 September 2003 Melbourne, Victoria, Australia http://www.swin.edu.au/lasers/ACOLS03 ACOLS03 is the region's showcase of research and development in all aspects of optics, lasers and spectroscopy, and provides a broad forum for discussion of these important areas. As with past successful conferences in this series, sessions will include a wide range of topics such as : * Spectroscopy * Lasers and laser applications * Optical imaging * Optical fibres * Atom optics and BEC * Quantum optics, coherence, information and computing * Photonics * Instrumentation and standards ACOLS03 will feature a comprehensive scientific and industrial trade exhibition, comprising a range of products and services relevant to the optics, lasers, and spectroscopy fields. If your company or organisation is interested in participating in the trade exhibition, contact the Conference Secretariat for further details. ------------------------------------------------------------------- IQING 3 -Informal Quantum Information Gathering European Workshop for PhD students and Postdocs 2-5 December 2003 Registration: 12 October 2003 MPQ Garching, Germany http://www.mpq.mpg.de/Theorygroup/CIRAC/public/IQING/ IQING3 is a small european workshop on quantum information science for postdocs, PhD students and master/diploma students. The aim is to bring young people together in a rather informal atmosphere to discuss new perspectives in the field, both in experiment and in theory. There will be three kinds of talks: * Tutorials on special topics, which the participants can suggest in their registration, * Open problems talks in which either an overview over a subject is given emphasizing the open problems in that field or a single interesting open problem is introduced, * Solved problems talks (20 min.) in which participants present their work. The concept of an open-problems-session is rather an "experiment" and we encourage in particular "senior postdocs" (but also everyone else) to offer these kinds of talks. ------------------------------------------------------------------- Solid State Quantum Information Processing 15-18 December 2003 Abstracts: October 1, 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. ------------------------------------------------------------------- 2nd Asia-Pacific Workshop on Quantum Information Science 15-19 December, 2003 Registration (+financial support request): September 30, 2003 Registration: October 19, 2003 Abstracts: October 31, 2003 Singapore http://www.physics.nus.edu.sg/%7Equantum/workshop/ Quantum Information Science is a fascinating interdisciplinary area that continues to capture the interest of physicists, mathematicians, chemists, engineers and computer scientists in recent years. In April 2001, we successfully organized a small scale international pedagogical workshop on the subject. Since then, there has been immense progress in this field. We have therefore decided to organise the Second Asia-Pacific Workshop on Quantum Information Science 2003 which will be held at the National University of Singapore from July 21, 2003 to 25 July, 2003. As in the previous workshop, the invited speakers will be delivering pedagogical talks on their areas of expertise and we will also be organising a special session for participants to share their findings through short oral presentations and poster exhibitions. Objectives: * To provide good pedagogical and introductory courses for researchers and graduate students who would like to learn about quantum information science * To promote exchanges of scientific knowledge in the field * To strengthen the ties among the scientists of the region who work in this area ------------------------------------------------------------------- QIP 2004: 7th Workshop on Quantum InformationProcessing 15th - 19th January 2004 Waterloo, Canada http://www.iqc.ca/conferences/qip/index.html Quantum information processing is the recasting of computer science in a quantum mechanical framework. It tries to improve on classical computers and classical complexity bounds by making use of quantum mechanical phenomena. After Peter Shor's 1994 discovery of efficient quantum algorithms for factoring and the discrete log (threatening current "classical" cryptography), the field has grown explosively and is now one of the most active subfields of both computer science and physics. QIP 2004 is the seventh workshop on quantum computing, quantum cryptography, and quantum information theory in the tradition of AQIP 98 in Aarhus, AQIP 99 in Chicago, QIP 2000 in Montreal, QIP 2001 at the CWI in Amsterdam, QIP 2002 at IBM in Yorktown Heights, and QIP 2003 at MSRI, Berkeley. The conference will run from Thursday 15 January until Monday 19 January. It will consist of various invited talks, a display of posters, and an open session. ------------------------------------------------------------------- Quantum Information Theory: Current Status & Future Directions 23rd - 27th August 2004 Cambridge, U.K. http://www.newton.cam.ac.uk/programmes/QIS/qisw01.html This conference will take place during the Newton Institute Programme on Quantum Information Science. It will bring together physicists, computer scientists and mathematicians to discuss the current status of the field and present important recent developments. Despite substantial progress in the last few years, there are also very many open questions and fundamental issues to be understood; thus, particular emphasis will be put on reviewing the major challenges in the field. Subjects covered by the conference will include, but are not restricted to, quantum algorithms and algorithmic techniques, quantum communication and quantum cryptography, quantum entanglement and non locality, fault tolerant quantum information processing and communication, quantum information processing and quantum operations under constraints (for instance imposed by the physical system in which they are realised).