Quantum Institute: Visitor Schedule

The Quantum Lunch is regularly held on Thursdays in the Theoretical Division Conference Room, TA-3, Building 123, Room 121.

The organizing committee includes Ryan O. Behunin (T-4 & CNLS), Malcolm Boshier (P-21), Adolfo del Campo (T-4 & CNLS), Michael Di Rosa (C-PCS), Ivar Martin (T-4), Changhyun Ryu (P-21), Rolando D. Somma (T-4), Christopher Ticknor (T-1), and Wojciech H. Zurek (T-4).

For more information, or to nominate a speaker, contact Adolfo del Campo.

To add your name to the Quantum Lunch email list, contact Ellie Vigil.

Thursday, March 28, 2013
12:30 PM - 2:00 PM

Speaker: Oscar Viyuela (Universidad Complutense de Madrid)

Technical Host: Adolfo del Campo

TOPIC: Density Matrix Topological Insulators: Thermal and decoherent effects playing a crucial role in the notion of topological order

Abstract
The stability of topological phases of matter, also known as topological orders, against thermal noise has provided several surprising results in the context of topological codes used in topological quantum information. However, very little is known about the behavior of a topological insulator (TI) subject to the disturbing thermal effect of its surrounding environment. This is of great relevance if we want to address key questions such as the robustness of TIs against thermal noise, existence of thermalization processes, use of TIs as platforms for quantum computation, etc.

We have studied [1] how protected edge states become unstable on a 1D topological insulator (TI) despite the interaction with the bath preserving the protecting symmetry of the TI. Due to this fact, in a recent work [2] we addressed the problem of how to generalize the notion of topological order to dissipative systems. We find interesting results like a new topological invariant at T != 0, the presence of mixed edge states at the boundary, etc. We are also able to link this new topological invariant to a physical observable like the transverse Hall conductivity -which at T != 0 is not topological invariant. To make our formalism concrete, we apply these concepts to the two-dimensional graphene-like Haldane model in the presence of thermal dissipation, but our results hold for arbitrary dimensions and density matrices.

[1] "Thermal Instability of Edge states in a 1D Topological Insulator", O. Viyuela, A. Rivas, M.A. Martín-Delgado, Phys. Rev. B 86, 155140 (2012)

[2] "Density Matrix Topological Insulator", A. Rivas, O. Viyuela, M.A. Martín-Delgado, arXiv: 1301.4872