Quantum Information II

We focus on aspects of robust quantum computation, quantum entanglement, and open quantum systems.

We develop new types of robust holonomic gates for quantum gates, based on non-adiabatic geometric phases [1] and combine them with other error resilient techniques [2]. Quantum entanglement with focus on many-qubit systems is analyzed by means of gauge theoretical [3] and topological methods [4]. Quantum coherence and correlations in non-Markovian open system dynamics with applications to biological systems are studied [5]. We work on various other topics in quantum mechanics, such as Berry phases, weak measurements, photon and neutron optics, as well as cold atom dynamics.

[1] E. Sjöqvist, D. M. Tong, L. M. Andersson, B. Hessmo, M. Johansson, and K. Singh, “Non-adiabatic holonomic quantum computation”, New J. Phys. 14, 103035 (2012).
[2] G. F. Xu, J. Zhang, D. M. Tong, E. Sjöqvist, and L. C. Kwek, “Non-adiabatic holonomic quantum computation in decoherence-free subspaces”, Phys. Rev. Lett. 109, 170501 (2012).
[3] M. Williamson, M. Ericsson, M. Johansson, E. Sjöqvist, A. Sudbery, and V. Vedral, “Global asymmetry of many-qubit correlations: A lattice-gauge-theory approach.” Phys. Rev. A 84, 032302 (2011).
[4] M. Johansson, M. Ericsson, K. Singh, E. Sjöqvist, and M. S. Williamson, “Topological phases and multiqubit entanglement”, Phys. Rev. A 85, 032112 (2012).
[5] C. Bengtson, M. Stenrup, and E. Sjöqvist, “Quantum nonlocality in the excitation energy transfer in the Fenna-Matthews-Olson complex”, Int. J. Quantum Chem. 116, 1763 (2016).