Speaker: Pinja Haikka, Turku University, Finland

Title: Non-Markovian quantum probes

Time: Thursday, February 21, 2013

Place: 1525-323

Quantum probes interacting with complex systems can be used to extract information about the system they are interacting with, ideally in a non-destructive way. In an open quantum system approach, the interaction of a qubit probe with a complex environment gives rise to decoherence phenomena, affecting the qubit dynamics. Due to the nontrivial structure of the environment, the qubit evolution is typically characterized by partial information backflow, i.e., by non-Markovian effects [1]. It has been shown that non-Markovianity of a qubit probe is a useful characterization of the complex system dynamics in the context of, for example, ultracold gases [2].?? In this talk I will briefty introduce a recently proposed measure of non-Markovianity [1]. I will then use this measure to present two examples of non-Markovianity as a quantum probe for critical many-body environments. The two physical models I discuss are the Ising model in a transverse filed, probed by a central spin [3] and a 1D Coulomb crystal undergoing a second order phase transition from a linear to a zigzag structure, probed with Ramsey interferometry [4]. For both models the critical features of the environment are beautifully manifested in the non-Markovianity of the probe qubit.

[1] H.-P. Breuer, E.-M. Laine, J. Piilo, Phys. Rev. Lett. 103, 210401 (2009).

[2] P. Haikka, S. McEndoo, G. De Chiara, G. M. Palma and S. Maniscalco, Phys.   Rev. A 84 031602(R) (2013) and Physica Scripta T151, 014060 (2012); P. Haikka, S. McEndoo and S. Maniscalco, Phys. Rev. A 87, 012127 (2013).

[3] P. Haikka, J. Goold, S. McEndoo, F. Plastina and S. Maniscalco, Phys. Rev. A 85 060101(R) (2012).

[4] M. Borrelli, P. Haikka, G. De Chiara and S. Maniscalco, in the arxiv mon/tue, will update this.

Coffee, tea and cake will be served from 15.00.