QLunch: Robert Jonsson

Speaker: Robert Jonsson, Stockholm University, Sweden

Title: Gaussian states, partner modes and an entanglement duality

Abstract: 

Gaussian states appear everywhere in quantum physics - from condensed matter, to quantum optics and quantum field theory in curved spacetimes.
In this talk I aim for three objectives: First, I discuss the entanglement structure of Gaussian states which is well known, but maybe not widely known. Under a bipartition of a Gaussian state partner modes arise which are found both in Einstein-Bose condensates or the Unruh effect.
Second, I review the powerful Kähler structure formalism for Gaussian states. It both captures the geometry of Gaussian states and is practical for applications, and it treats both bosons and fermions simultaneously.
Third, to showcase an example connecting bosonic and fermionic systems, I will present an entanglement duality which arises in supersymmetric Gaussian states [1]. Here, bosonic and fermionic partner subsystems, canonically identified by the supercharge construction, exhibit an intriguing duality of their entanglement spectra.
Time permitting, as a special application, we consider topological insulators and superconductors and their SUSY partners, discussing the recently derived classification of supercharges in this context [2].

[1] Jonsson, Robert H., Lucas Hackl, and Krishanu Roychowdhury. “Entanglement Dualities in Supersymmetry.” Physical Review Research 3, no. 2 (June 16, 2021): 023213.
[2] Gong, Zongping, Robert H. Jonsson, and Daniel Malz. “Supersymmetric Free Fermions and Bosons: Locality, Symmetry, and Topology.” Physical Review B 105, no. 8 (February 24, 2022): 085423.