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453. WE-Heraeus-Seminar
Quantum communication based on integrated optics

Physikzentrum Bad Honnef

March 22nd - 25th 2010, 4 Days

Scientific head:
Christine Silberhorn and Gerd Leuchs

Max Planck Institute for the Science of Light
Guenther-Scharowsky-Str.1/Building 24
D-91058 Erlangen
Tel.: +49(0)9131-6877-101
Fax: +49(0)9131-6877-109
web: http://www.mpl.mpg.de

Seminar contents and program:

Scientific background:

Quantum communication utilizes genuine quantum characteristics of light to accomplish communication tasks, which cannot be achieved by classical information transfer. Most prominently quantum cryptography allows two parties to communicate secretly with unconditional security, i.e. - in contrast to classical encryption protocols - the laws of quantum physics themselves ensure that the presence of an eavesdropper can be detected with certainty during the transmission of an secret key transmission. Other quantum communication protocols, such as quantum teleportation or quantum dense coding, enable the mapping of quantum information from one information carrier to a different one, e.g. from photonic states to the quantum states of atoms, or allow for an enhanced information transfer per sent signal state. All these concepts have in common that their implementation in practical systems requires the preparation of non-classical states with an excellent control of all system parameters and a precise characterization of the signal states and measurement process.

The definition of a quantum bit, or qubit, intrinsically assumes an information carrier, which contains exactly one quantum. For light states this means that single photon states are needed for the encoding of genuine qubits, but laser light never exhibits a precise photon number. Thus several routes have been pursued to overcome this problem: idealized theoretical protocols have been generalized to enable the use of laser light; novel, so-called continuous variable protocols suggest the use of laser light and/or squeezed light in combination with homodyne detection to design quantum communication systems, which exploit an Heisenberg uncertainty relation as quantum property; and new state detection methods and more advanced light sources based on a non-linear interaction between light and matter have been developed, which allow for the generation of improved quantum states, e.g. photon pairs with de-coupled or highly entangled modal properties.

In the last years the field has witnessed remarkable progress, such that more and more advanced systems can nowadays be implemented with decreasing costs but increasing complexity. Quantum key distribution systems have matured to a real-word application, such that they are now commercially available from several companies. In this context, practical aspects, such as stability, compactness and user friendly operation become more and more important. This, in turn, requires a consistent development of a novel technology adapted to the needs of quantum state engineering. One major challenge in up-to-date quantum communication systems remains to be solved: experimental imperfections of quantum channels limit drastically the maximum distance and bit rates for quantum information transfer. Theoretical proposals have shown that building up quantum repeater systems can solve these limitations, however, their experimental realization requires quantum networks with multiple quantum input states and efficient coupling between different channels.

An important step in this context is the exploitation of integrated optic devices to realize such complex linear quantum networks. Several research groups around the world have now started to investigate systematically sources of non-classical light, which are based on optical fibers and/or non-linear waveguides. Similar devices have been investigated for other applications, e.g. the generation of different wavelengths using second harmonic generation or four wave mixing, such that highly efficient integrated optics elements have become available for future quantum communication applications. Current research work tests their suitability for state preparation, manipulation and state detection setups. Linear optical networks in combination with appropriate state detection enable a more sophisticated state manipulation and constitute a building block for future quantum communication tasks. Integrated optical circuits can ensure interferometric phase stability between different channels within a network and first experiments have already proven that this approach appears promising for the development of more advanced systems.

Based on linear optical systems new theoretical protocols are studied with the attempt to reduce the required experimental resources, especially those of high cost, i.e. which are hard to realize in practical systems. For example, an interesting concept combines continuous variable systems and single photons or photon counting to establish improved quantum information encoding with an optimized use of existing resources. Moreover, protocols for more applications of quantum communication systems with increased complexity have been developed over the last years. These are at the edge of being realistic for experimental testing in the laboratories. This provides a fruitful background to explore the potential of photonic state manipulation at the quantum level.


This seminar which is kindly supported by the Wilhem and Else Heraeus Foundation will bring together international experts with complementary experience and know-how including theoretical aspects as well as experimental issues related to the topic of quantum communication using linear optics and integrated devices. The developments over the last years have led to a large increase of knowledge, which is typically not yet published in textbooks and is often not taught at the universities. The seminar is primarily intended to provide a good introduction for newcomers in the field, especially for PhD students and young post-docs, but it should also provide a good overview of recent developments. Bringing together an international group of young researchers will further initiate mutually beneficial exchanges between these groups and can be expected to stimulate stronger collaborations in the field between the participating research groups.

Preliminary list of invited speakers:

  • Ulrik Andersen, Technical University of Denmark
  • Dagmar Bruß, University of Düsseldorf, Germany
  • Konrad Banaszek, University of Warsaw, Poland
  • Jeromy O’Brien, University of Bristol, UK
  • Alexander Gaeta, Cornell University, USA
  • Hugues de Riedmatten, University of Geneva, Switzerland
  • Prem Kumar, Northwestern University, Evanston, USA
  • Peter van Loock, University of Erlangen, Germany
  • Martin Plenio, University of Ulm, Germany
  • Tim Ralph, University of Queensland, Australiali
  • Philip Russell, MPL, Erlangen, Germany
  • John Rarity, University of Bristol, UK
  • Wolfgang Sohler, University of Paderborn, Germany
  • Ian Walmsley, University of Oxford, UK
  • Harald Weinfurter, LMU University of Munich, Germany
  • Sebastien Tanzilli, CNRS Universite de Nice Sophia Antipolis, Frannce


  Monday Tuesday Wednesday Thursday
08:00am - 09:30am Talk Talk Talk Talk
09:45am - 11:15am Talk Talk Talk Talk
11:15am - 12:45pm Talk Talk Talk Talk
12:45pm - 02:15pm Lunch Lunch Lunch Lunch
02:15pm - 03:45pm Poster Excursion Poster Talk
04:00pm - 05:30pm Talk Excursion Talk Talk
05:30pm - 06:30pm Welcome Dinner Dinner Dinner Dinner
07:00pm - 08:30pm Welcome Dinner Poster Discussion Discussion

Registration (Deadline: January 31st, 2010):

  • No conference fee will be charged, local expenses for accommodation and food will be covered (the seminar is kindly supported by the Heraeus Foundation)
  • The maximal number of applicants is limited to 40
  • The registration deadline January 31st, 2010
  • You will receive an application confirmation by the Heraeus Foundation in February.