University of PotsdamPhysics DepartmentInterdisciplinary Centre for Photonics

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Quantum information theory


Quantum many-body theory


Quantum optics


Cold atoms in optical lattices


Open quantum systems




 

Quantum information theory:


Quantum information science asks what information processing tasks are possible if single quantum systems are used as elementary carries of information. The ability to coherently manipulate the state of a quantum system allows for tasks that are thought to be unachievable in the classical context - such as secure transmission of information - or for the efficient solution of computational problems for which no classical efficient algorithm is known.

We ask - with methods of mathematical physics - questions of how to grasp entanglement, giving rise to quantum correlations that are stronger than classically attainable, of quantum channel capacities, and of new quantum computational models, based on quantum many-body ideas and tensor networks. Recently newly acquired interest is concerned with pseudo-random states and operations in quantum expanders and unitary designs, as well as questions of concentration of measure and classical percolation ideas.

A main theme recently is first and foremost the idea of quantum systems identification: Often, one can much more efficiently and cheaply estimate intricate properties of quantum systems, without the need of full quantum state or process tomography. Using the idea of compressed sensing, even full quantum state tomography can be made for low rank states with about the square root of the previously known effort. Quantum information ideas are often a guiding principle in work that is not directly related to information processing as such.

For a comprehensive list of tutorials and review articles, see this link.

For popular articles about our work, see this link.

              
Selected group publications:
  • "Novel schemes for measurement-based quantum computation",
    Physical Review Letters 98, 220503 (2007).
  • "Percolation, renormalization, and quantum computing with non-deterministic gates",
    Physical Review Letters 99, 130501 (2007).
  • "Entanglement combing",
    Physical Review Letters 103, 220501 (2009).
  • "Quantum state tomography via compressed sensing",
    arXiv:0909.3304.
  • "Multi-particle entanglement in graph states",
    Physical Review A 69
    , 062311 (2004).
  • "Covariance matrices and the separability problem",
    Physical Review Letters 99, 130504 (2007).
  • "Classical information and distillable entanglement",
    Physical Review Letters 84, 1611 (2000).
  • "The asymptotic relative entropy of entanglement",
    Physical Review Letters 87, 217902 (2001).
  • "Quantum Margulis expanders",
    Quantum Information and Computation 8, 722 (2008),
  • "Gaussian quantum marginal problem",
    Communications in Mathematical Physics 280, 263 (2008).
  • "Quantitative entanglement witnesses",
    New Journal of Physics 9, 46 (2007).
  • "Optimal local implementation of non-local quantum gates",
    Physical Review A 62, 052317 (2000).
  • "Classical information capacity of a class of quantum channels",
    New Journal of Physics 7, 93 (2005).
  • "Evenly distributed unitaries: on the structure of unitary designs",
    Journal of Mathematical Physics 48, 052104 (2007).
  • "Correlated entanglement distillation and the structure of the set of undistillable states",
    Journal of Mathematical Physics 49, 042102 (2008).
  • "Complete hierarchies of efficient approximations in entanglement theory",
    Physical Review A 70, 062317 (2004).
  • "Quantum games and quantum strategies",
    Physical Review Letters 83, 3077 (1999).
  • "The entanglement cost under PPT operations"
    Physical Review Letters 90, 027901 (2003).
  • "Quantification of entanglement in infinite-dimensional quantum systems",
    Journal of Physics A 35, 3911 (2002).
  • "Potential and limits to cluster state quantum computing using probabilistic gates",
    Physical Review A 74, 062317 (2006).


    Group tutorials and review articles:
  • "Quantum computing",
    In:
    "Handbook of Nature-Inspired and Innovative Computing" Eds. A. Zomaya, G. Milburn et al. (Springer, Heidelberg, 2006).
  • "Introduction to the basics of entanglement theory in continuous-variable systems",
    Int. J. Quant. Inf. 1, 479 (2003).
  • "Gaussian quantum channels",
    In: "Continuous-variable quantum information science", Eds. E. Polzik, N. Cerf, G. Leuchs (Imperial College Press, London, 2007).
  • "Multi-partite entanglement",
    In: "Quantum Information Theory", Eds. D. Bruss, G. Leuchs (VCH, Weinheim, 2007).
  • "Quantum information and percolation theory",
    In: "Quantum percolation and breakdown" (Springer, Heidelberg, 2008).