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arXiv · 2412.05870

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

Y. -Y. Chen·K. Li·L. Zhang·Y. -K. Wu·J. -Y. Ma·H. -X. Yang·C. Zhang·B. -X. Qi·Z. -C. Zhou·P. -Y. Hou·Y. Xu·L. -M. Duan
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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.

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Y. -Y. Chen, K. Li, L. Zhang, Y. -K. Wu, J. -Y. Ma, H. -X. Yang, C. Zhang, B. -X. Qi, Z. -C. Zhou, P. -Y. Hou, Y. Xu, L. -M. Duan. 2024-12-08. Quantum tomography of a third-order exceptional point in a dissipative trapped ion. https://doi.org/10.1038/s41467-025-62573-5

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