Quantum information science asks what information processing tasks are possible if single quantum systems are used as elementary carriers 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 inherently 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 what manipulation of quantum information is possible. A recent emphasis has been to understand the precise computional power of quantum devices.

Selected group publications

• Closing gaps of a quantum advantage with short-time Hamiltonian dynamics,
  J. Haferkamp, D. Hangleiter, A. Bouland, B. Fefferman, J. Eisert, J. Bermejo-Vega,
  Physical Review Letters 125, 250501 (2020)
• On the quantum versus classical learnability of discrete distributions,
  R. Sweke, J.-P. Seifert, D. Hangleiter, J. Eisert,
  Quantum 5, 417 (2021)
• Stochastic gradient descent for hybrid quantum-classical optimization
  Quantum 4, 314 (2020)
• Architectures for quantum simulation showing a quantum speedup
  Physical Review X 8, 021010 (2018) 
• Subsystem symmetries, quantum cellular automata, and computational phases of quantum matter
  Quantum 3, 142 (2019) 
• Most quantum states are too entangled to be useful as computational resources
  Physical Review Letters 102, 190501 (2009)
• Novel schemes for measurement-based quantum computation
  Physical Review Letters 98, 220503 (2007)
• Precisely timing dissipative quantum information processing
  Physical Review Letters 110, 110501 (2013) 
• Full randomness from arbitrarily deterministic events
  Nature Communications 4, 2654 (2013)
• Entanglement combing
  Physical Review Letters 99, 130501 (2007)
• Quantum measurement occurrence is undecidable
  Physical Review Letters 108, 260501 (2012) 
• Matrix product operators and states: NP hardness and undecidability
  Physical Review Letters 113, 160503 (2014) 
• Percolation, renormalisation, and quantum computing with non-deterministic gates
  Physical Review Letters 100, 130501 (2007)
• Full randomness from arbitrarily deterministic events
  Nature Communications 4, 2654 (2013) 
• Quantitative entanglement witnesses
  New Journal of Physics 9, 46 (2007) 
• Evenly distributed unitaries: On the structure of unitary designs
  Journal of Mathematical Physics 48, 052104 (2007)
• Gaussian quantum marginal problem
  Communications in Mathematical Physics 280, 263 (2008) 

• The complexity of relating quantum channels to master equations
  Communications of Mathematical Physics 310, 383 (2012)
  

Group reviews

• Quantum coherence as a resource
  Reviews of Modern Physics 89, 041003 (2017)
• Multi-particle entanglement
  In: Quantum Information Theory, Eds. D. Bruss, G. Leuchs (VCH, Weinheim, 2007)
• Introduction to the basics of entanglement theory in continuous-variable systems
  International Journal of Quantum Information 1, 479 (2003) 
• Quantum computing
  In: Handbook of Nature-Inspired and Innovative Computing, Eds. Zomaya, G. Milburn et al (Springer, 2006)
• Gaussian quantum channels
  In: Continuous-variable quantum information science, Eds. E. Polzik, N. Cerf, G. Leuchs, (Imperial College Press, 2007)
• Quantum information and percolation theory
  In: Quantum percolation and breakdown (Springer, 2008)