Entanglement in non-unitary critical spin chains (Romain Couvreur)
Max-Planck-Institut für Quantenoptik
MPQ, Theory Division
Entanglement entropy has proven invaluable to our understanding of quantum criticality. It is natural to try to extend the concept to “nonunitary quantum mechanics”, which has seen growing interest from areas as diverse as open quantum systems, noninteracting electronic disordered systems, or nonunitary conformal field theory (CFT).
I will discuss such an extension by focusing on physical
systems that can be described as geometrical loop models. In the thermodynamic
limit of unitary systems, the scaling of the entanglement entropy is known to
be related to a universal quantity called central charge. I will show how this
famous result is modified for the groundstates of non-hermitian Hamiltonians
and introduce the concept of effective central charge as a measurement of the
density of states.