Balanced gain and loss renders the mean-field description of Bose-Einstein condensates $\mathcal{PT}$ symmetric. However, any experimental realization has to deal with unbalancing in the gain and loss contributions breaking the $\mathcal{PT}$ symmetry. We will show that such an asymmetry does not necessarily lead to a system without a stable mean-field ground state. Indeed, by exploiting the nonlinear properties of the condensate, a small asymmetry can stabilize the system even further due to a self-regulation of the particle number.Balanced gain and loss renders the mean-field description of Bose-Einstein condensates $\mathcal{PT}$ symmetric. However, any experimental realization has to deal with unbalancing in the gain and loss contributions breaking the $\mathcal{PT}$ symmetry. We will show that such an asymmetry does not necessarily lead to a system without a stable mean-field ground state. Indeed, by exploiting the nonlinear properties of the condensate, a small asymmetry can stabilize the system even further due to a self-regulation of the particle number.

arXiv:1706.03489Physical Review AAug 16, 201713 citations

Three entangled photon dynamics in PT- and anti-PT-symmetric systems

Javed Akram

Jan 1, 20260 citations

Steering entanglement through exceptional points in non-hermitian cavity magnomechanics

Chenhui Yu, Wu-Ming Liu, Kashif Ammar Yasir

Cavity magnomechanical systems, which coherently couple magnons, photons, and phonons, offer a powerful platform for exploring quantum phenomena and developing hybrid quantum technologies. We study a non-Hermitian cavity magnomechanical system featuring a yttrium iron garnet (YIG) sphere driven by an external magnetic field, where magnons interact with cavity photons via magnetic dipole coupling and with phonons via magnetostrictive forces. Non-Hermiticity is introduced through a traveling optical field that directly excites the YIG sphere, enabling precise control over parity-time (PT) symmetry. Analysis of the eigenfrequency spectrum reveals a third-order exceptional point (EP) that demarcates distinct PT-symmetric phases: a unique configuration with coexisting broken and protected PT-symmetry regimes, tunable via the interplay of the traveling field strength and magnon-photon coupling. We also verify this by measuring the divergence around EP with Petermann Factor. Crucially, the system exhibits stable PT-symmetry only at specific field incidence angles, with instability or broken symmetry dominating elsewhere. Beyond PT-symmetry, we demonstrate robust quantum entanglement among the magnon, photon, and phonon subsystems. The exceptional point serves as a critical boundary, with unbroken and broken PT symmetry phases enabling dynamic entanglement swapping between subsystem pairs. By modulating the non-Hermitian parameters, we achieve controlled entanglement transfer and suppression of fluctuations, highlighting the system’s potential for quantum information processing. These results establish a direct connection between non-Hermitian topology, dynamical stability, and quantum correlations, providing a framework for leveraging PT symmetry in cavity magnomechanics for quantum technologies.Cavity magnomechanical systems, which coherently couple magnons, photons, and phonons, offer a powerful platform for exploring quantum phenomena and developing hybrid quantum technologies. We study a non-Hermitian cavity magnomechanical system featuring a yttrium iron garnet (YIG) sphere driven by an external magnetic field, where magnons interact with cavity photons via magnetic dipole coupling and with phonons via magnetostrictive forces. Non-Hermiticity is introduced through a traveling optical field that directly excites the YIG sphere, enabling precise control over parity-time (PT) symmetry. Analysis of the eigenfrequency spectrum reveals a third-order exceptional point (EP) that demarcates distinct PT-symmetric phases: a unique configuration with coexisting broken and protected PT-symmetry regimes, tunable via the interplay of the traveling field strength and magnon-photon coupling. We also verify this by measuring the divergence around EP with Petermann Factor. Crucially, the system exhibits stable PT-symmetry only at specific field incidence angles, with instability or broken symmetry dominating elsewhere. Beyond PT-symmetry, we demonstrate robust quantum entanglement among the magnon, photon, and phonon subsystems. The exceptional point serves as a critical boundary, with unbroken and broken PT symmetry phases enabling dynamic entanglement swapping between subsystem pairs. By modulating the non-Hermitian parameters, we achieve controlled entanglement transfer and suppression of fluctuations, highlighting the system’s potential for quantum information processing. These results establish a direct connection between non-Hermitian topology, dynamical stability, and quantum correlations, providing a framework for leveraging PT symmetry in cavity magnomechanics for quantum technologies.

npj Quantum MaterialsDec 3, 20255 citations

Entanglement negativity in non-Hermitian PT -symmetric models

L.S. Lima

Physica E Low-dimensional Systems and NanostructuresApr 17, 20255 citations

Effects of unbalanced detection on the photon statistics of single-molecule photon source

Wang Tie-yun, Liantuan Xiao

Theoretical research on the record of every incident output of the single-molecule photon source responded by two SPCM with standard Hanbury-Brown-Twiss technique is presented.The photon statistic measurement of a single molecule photon source based on the HBT configuration with an unbalanced detection system is studied.The photon counting statistics character of the real single molecular photon source with a Poisson statistics background is theoretically investigated.It is shown that the unbalanced detectors,the unbalanced beam-splitter and the unbalanced linear propagation efficiencies will cause the single event Mandel parameter to be less than that of balance system.In addition,the correction expression to the Mandel parameter based on unbalanced detection is given.Theoretical research on the record of every incident output of the single-molecule photon source responded by two SPCM with standard Hanbury-Brown-Twiss technique is presented.The photon statistic measurement of a single molecule photon source based on the HBT configuration with an unbalanced detection system is studied.The photon counting statistics character of the real single molecular photon source with a Poisson statistics background is theoretically investigated.It is shown that the unbalanced detectors,the unbalanced beam-splitter and the unbalanced linear propagation efficiencies will cause the single event Mandel parameter to be less than that of balance system.In addition,the correction expression to the Mandel parameter based on unbalanced detection is given.

Journal of Applied OpticsJan 1, 20060 citations

Two-Photon Spin States and Entanglement States

Xiaojing Liu, Xiang-Yao Wu, Jingbin Lu +9 more

arXiv:1401.2152International Journal of Theoretical PhysicsMay 1, 20142 citations

Balanced gain and loss renders the mean-field description of Bose-Einstein condensates

\mathcal{PT}

symmetric. However, any experimental realization has to deal with unbalancing in the gain and loss contributions breaking the

\mathcal{PT}

symmetry. We will show that such an asymmetry does not necessarily lead to a system without a stable mean-field ground state. Indeed, by exploiting the nonlinear properties of the condensate, a small asymmetry can stabilize the system even further due to a self-regulation of the particle number.