Abstract: Open systems with gain or losses, or both, described by non-Hermitian Hamiltonians, have been a subject of intense research recently.
In classical optical systems, the effect of exceptional-point degeneracies on their dynamics has been observed through remarkable phenomena
such as the parity-time (PT) symmetry breaking transition, asymmetric mode switching, and optimal energy transfer.
After a brief history of the field of PT-symmetry, started by Carl Bender and co-workers, I will discuss quantum realizations of such systems with
single photons, ultracold atoms, and superconducting transmon circuits. Results include observation of PT transitions at vanishingly small non-Hermiticity
in the Floquet domain, information flow in a PT-symmetric system, and a quantum signature of the exceptional point in the qubit relaxation state.
I will argue that non-Hermiticity provides a new dimension for exploring quantum systems.
* Work in collaboration with Dr. Anthony Laing (University of Bristol), Prof. Le Luo (Sun Yat-Sen University), and Prof. Kater Murch (Washington U.).