Quantum tomography of a third-order exceptional point in a dissipative trapped ion

TL;DR

This paper experimentally demonstrates a third-order exceptional point in a dissipative trapped ion system by employing non-Hermitian Hamiltonian dynamics and quantum state tomography, revealing topological properties and potential quantum tech applications.

Contribution

It introduces methods to realize and observe third-order exceptional points in open quantum systems using trapped ions, advancing non-Hermitian quantum physics research.

Findings

Successful observation of third-order exceptional point via spectroscopy

Demonstration of eigenstate coalescence through quantum state tomography

Identification of an intrinsic third-order Liouvillian exceptional point

Abstract

The requirement for Hermiticity in quantum mechanics ensures the reality of energies, while the parity-time symmetry offers an alternative route to achieve this goal. Interestingly, in a three-level system, the parity-time symmetry-breaking can lead to a third-order exceptional point with distinctive topological properties and enhanced sensitivity. To experimentally implement this in open quantum systems, it is essential to introduce two well-controlled loss channels. However, the requirement for these two loss channels presents a challenge in experimental implementation due to the lack of methods to realize the dynamics governed by an effective non-Hermitian Hamiltonian. Here we address the challenge by employing two approaches to eliminate the effects of quantum jump terms so that the dynamics is governed by an effective non-Hermitian Hamiltonian in a dissipative trapped ion with two loss channels. Based on this, we experimentally observe the parity-time symmetry-breaking-induced third-order exceptional point through non-Hermitian absorption spectroscopy. In particular, we perform quantum state tomography to directly demonstrate the coalescence of three eigenstates into a single eigenstate at the exceptional point. Finally, we identify an intrinsic third order Liouvillian exceptional point associated with a parity-time symmetry breaking via quench dynamics. Our experiments can be extended to observe other non-Hermitian phenomena involving more than two levels and potentially find applications in quantum information technology.