# Non-adiabatic transitions through exceptional points in the band structure of a PT-symmetric lattice

## TL;DR

This paper analytically investigates non-adiabatic transitions at exceptional points in a PT-symmetric lattice, revealing how finite-speed parameter changes affect state redistribution and proposing experimental observation via Bloch oscillations.

## Contribution

The study derives an analytical expression for non-adiabatic transition probabilities through exceptional points in a PT-symmetric lattice, linking theory with experimental feasibility.

## Key findings

- Transition probabilities depend on the speed of parameter variation.
- Equal redistribution occurs in the adiabatic limit at exceptional points.
- Experimental setup with Bloch oscillations can observe these effects.

## Abstract

Exceptional points, at which two or more eigenfunctions of a Hamiltonian coalesce, occur in non-Hermitian systems and lead to surprising physical effects. In particular, the behaviour of a system under parameter variation can differ significantly from the familiar Hermitian case in the presence of exceptional points. Here we analytically derive the probability of a non-adiabatic transition in a two-level system driven through two consecutive exceptional points at finite speed. The system is Hermitian far away from the exceptional points. In the adiabatic limit an equal redistribution between the states coalescing in the exceptional point is observed, which can be interpreted as a loss of information when passing through the exceptional point. For finite parameter variation this gets modified. We demonstrate how the transition through the exceptional points can be experimentally addressed in a PT-symmetric lattice using Bloch oscillations.