Observation of $\mathcal{P}\mathcal{T}$-symmetric quantum coherence in a single ion system

Abstract

Parity-time($\mathcal{P}\mathcal{T}$)-symmetric systems, featuring real eigenvalues despite its non-Hermitian nature, have been widely utilized to achieve exotic functionalities in the classical realm, such as loss-induced transparency or lasing revival. By approaching the exceptional point (EP) or the coalescences of both eigenvalues and eigenstates, unconventional effects are also expected to emerge in pure quantum $\mathcal{P}\mathcal{T}$ devices. Here, we report experimental evidences of spontaneous $\mathcal{P}\mathcal{T}$ symmetry breaking in a single cold ${}^{40}{\mathrm{Ca}}^{+}$ ion, and more importantly, a counterintuitive effect of perfect quantum coherence occurring at the EP. Excellent agreement between experimental results and theoretical predictions is identified. In view of the versatile role of cold ions in building quantum memory or processor, our experiment provides a new platform to explore and utilize pure quantum EP effects, with diverse applications in quantum engineering of trapped ions.

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• Experimental demonstration of coherence flow in $\mathcal{P}\mathcal{T}$- and anti-$\mathcal{P}\mathcal{T}$-symmetric systems
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• Generalised quantum speed limit for arbitrary time-continuous evolution
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• PT-symmetric quantum Rabi model
• Quantum state discrimination in a PT-symmetric system
• Probing two-body exceptional points in open dissipative systems
• Chiral quantum heating and cooling with an optically controlled ion
• Experimental demonstration of enhanced violations of Leggett-Garg inequalities in a $\mathcal{P}\mathcal{T}$-symmetric trapped-ion qubit
• Quantum fluctuations on top of a $\mathcal{P}\mathcal{T}$-symmetric Bose-Einstein Condensate
• Third-order exceptional point in an ion-cavity system
• Quantum tomography of a third-order exceptional point in a dissipative trapped ion
• Quantum Mpemba effect in parity-time symmetric systems
• Experimental demonstration of the dynamics of quantum coherence evolving under a PT-symmetric Hamiltonian on an NMR quantum processor
• Accelerating multipartite entanglement generation in non-Hermitian superconducting qubits
• $\mathcal{P}\mathcal{T}$-symmetric quantum Rabi model: Solutions and exceptional points
• Nonadiabatic transitions in non-Hermitian $\mathcal{P}\mathcal{T}$-symmetric two-level systems
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• Protection of quantum evolutions under parity-time symmetric non-Hermitian Hamiltonians by dynamical decoupling
• Controllable non-Hermitian qubit-qubit Coupling in Superconducting quantum Circuit
• Enhancement of vibrationally assisted energy transfer by proximity to exceptional points, probed by fluorescence-detected vibrational spectroscopy
• Vacuum Rabi Splitting and Quantum Fisher Information of a Non-Hermitian Qubit in a Single-Mode Cavity
• Observation of quantum temporal correlations well beyond Luders bound
• Topology and its detection in a dissipative Aharonov-Bohm chain
• Band structures under non-Hermitian periodic potentials: Connecting nearly-free and bi-orthogonal tight-binding models
• Robustness of entanglement in a non-Hermitian cavity-optomechanical system even away from exceptional points
• Witnessing criticality in non-Hermitian systems via entropic uncertainty relation
• $\mathcal{P}\mathcal{T}$-symmetric two-photon quantum Rabi models
• Nonreciprocity Induced Fractional Nonlinear Thouless Pumping
• Enhanced charging in open Rabi and Dicke quantum batteries
• Investigation of the Effect of Quantum Measurement on Parity-Time Symmetry