Abstract Non-Hermitian degeneracies, also known as exceptional points, have recently emerged as a new way to engineer the response of open physical systems, we construct non-Hermitian systems through atomic electromagnetically induced transparency structures, based on which we study energy-level high-dimensional quantized photon correlations under dressing field induced parity-time (PT) symmetry and symmetry breaking. We study the symmetry breaking through exceptional point (EP) control in dressing-controlled energy-level process is natural EP, which are born to be non-Hermitian without artificial photonic structures. When the dressing Rabi frequency (de-phase rate) dominates, the real part (imaginary part) splits, and leads to in-phase (out-of-phase) constructive (destructive) dressing quantization. It can also be used to develop atomic-like symmetry-breaking photonic chips and pseudo-spin devices in the future.
Abstract Non-Hermitian degeneracies, also known as exceptional points, have recently emerged as a new way to engineer the response of open physical systems, we construct non-Hermitian systems through atomic electromagnetically induced transparency structures, based on which we study energy-level high-dimensional quantized photon correlations under dressing field induced parity-time (PT) symmetry and symmetry breaking. We study the symmetry breaking through exceptional point (EP) control in dressing-controlled energy-level process is natural EP, which are born to be non-Hermitian without artificial photonic structures. When the dressing Rabi frequency (de-phase rate) dominates, the real part (imaginary part) splits, and leads to in-phase (out-of-phase) constructive (destructive) dressing quantization. It can also be used to develop atomic-like symmetry-breaking photonic chips and pseudo-spin devices in the future.
The concept of non‐Hermitian systems, also known as exceptional points (EPs), has recently emerged as a novel approach for designing the response of systems that exchange energy with the external environment. The system behaves as a non‐Hermitian Hamiltonian (NH Hamiltonian), the real part of which is related to the internal dynamics of the system, and the imaginary part reflects the energy exchange between the system and the outside environment. By utilizing double EIT windows and adjusting the intensity of the dressing field, the number and positions of eigenvalues can be modulated to construct quantum entanglement sources for non‐Hermitian systems, thereby laying the foundation for quantum communication and quantum computing. To prepare photon entanglement sources, it is necessary to study the correlation of high‐dimensional quantized energy levels under PT symmetry and symmetry breaking induced by the dressing field; Hamiltonian correlation matrix of the non‐Hermitian system characterizes the relationship between gain and loss, detuning and dephasing rate in the reaction energy‐level system, and the coupling relationship of the dressing field. The energy‐level system itself is non‐Hermitian, and the study of symmetry breaking is conducted by controlling EPs during the level control process through the dressing field, thus eliminating the need for introducing artificial photonic structures. The third‐order non‐Hermitian characteristics of the PT‐NH system reflect the positional relationship between the cascade field and the nested field. When the Rabi frequency (dephase rate) of the dressing field is the dominant factor, the real (imaginary) part of the eigenvalues is split, resulting in in‐phase (out‐of‐phase) constructive (destructive) transformations of the dressing order.
A natural non- Hermitian system is constructed based on 85Rb atoms and multi-dressing fields. On this basis, the influence of different dressing fields on symmetry breaking and energy level degeneracy during four-photon spontaneous eight-wave mixing based on seventh-order nonlinear effects is investigated, and four-photon correlations are analyzed. When the dressing Rabi frequency dominates, the real part splits, leading to in phase constructive dressing, its symmetry breaking is localized, non-degenerate, Abelian and has low symmetry. When the dephase rate dominates, the imaginary part splits, leading to out-of-phase destructive dressing, its symmetry breaking is nonlocal, degenerate, non- Abelian and highly symmetric. The interactions between the dressing fields and the eigenvalue splitting modes of two double dressing effects that have third-order EPs are compared, and the role of the internal and external dressing fields in the formation of third-order EPs is clarified. The third-order non-Hermitian interaction between two dressing fields of the nested scheme is strongest and weakest for the parallel scheme, with the cascade scheme intermediate between them. This study is of value for the detection and quantum storage of quantum states.
Abstract The non‐Hermitian singularity control of multimode entanglement in the energy‐level cascaded four‐wave mixing system within a single atomic vapor is of great significance and importance. In this study, a non‐Hermiticity system by means of quasi‐quantization of energy‐band based on non‐Hermiticity systems is constructed. By employing atomic coherence in the non‐Hermiticity system, high‐dimensional quantized photon correlations underdressed field‐induced parity‐time (PT) symmetry and symmetry breaking through the quantization of energy levels are studied. Such a phenomenon happens at microscopic (nanoscale) when the eigenvalues of dressed energy‐level and multimode entanglement are considered for both real and imaginary parts symmetry breaking. Double dressing effect is observed with more coherent channels and larger information capacity than single dressing in the energy‐level cascaded four‐wave mixing system. The study found that the splitting of the real part is larger than an imaginary part in a second‐order system, and the imaginary part splitting is also greater than the real part splitting in a third‐order system. The real part (in phase) is constructive dressing quantization, and the imaginary (out of phase) is destructive dressing quantization. Exceptional points (EP points) can be used to enhance sensitivity detection of entanglement quantum state.
Multipartite entanglement has emerged as a valuable quantum resource for constructing large-scale quantum networks. However, the presence of non-Hermitian features induced by natural microscopic quantum systems significantly modifies the overall response of nonlinear parametric processes, thereby enabling direct manipulation of multipartite entanglement properties. In this study, we demonstrate the generation of multimode entanglement through atomic four-wave mixing (FWM) and analyze the properties of exceptional points (EP) under dressing control in non-Hermitian systems. By leveraging dressing-controlled atomic nonlinearity, we achieve versatile EPs and higher-order EPs by carefully tuning the atomic multi-parameter in the cascading FWM system. Additionally, we investigate the entanglement properties of various permutations of the output signal modes using the positive partial transpose (PPT) criterion. Notably, under non-Hermitian control, the application of single-, double-, and N-dressing splits leads to coherent multichannel control and further extends the scale of quantum entanglement. The outcomes of our research offer a novel approach to actively control non-Hermitian quantum phenomena without relying on artificial photonic structures. Furthermore, this paves the way for the realization of complex quantum information tasks by exploiting the non-Hermitian characteristics of the light-matter interaction.
The response of open physical systems has recently been recognized as a novel way to engineer non-Hermitian degeneracies, also known as exceptional points (EPs). We investigate the fourth-order parity-time (PT) and anti-parity-time (APT) symmetries for phase conjugation and self-diffraction under spontaneous six-wave mixing (SSWM) processes across various dressing schemes, including parallel, parallel-cascade, parallel-nested, pure-nested, cascade-nested, pure-cascade, and nested-cascade triple dressing schemes. Our investigation reveals that during the “self-diffraction” process sequential fourth-order non-Hermitian interactions between nested and cascade-nested triple dressing fields, where the photon dressing Rabi frequency exhibits dominance, lead to the sequential fourth-order quantization characterized by five EPs. Meanwhile, a sequential third-order PT–APT quantization is governed by six EPs under the dominance of the dephasing rate. Pure-cascade and nested-cascade triple dressing schemes exhibit a third-order quantization accompanied by four EPs. Additionally, the differential interplay between two dressing dephasing rates yields eight EPs in the pure-cascade triple dressing scheme. In the context of phase conjugation, pure-nested and cascade-nested dominated by the photon dressing Rabi frequency manifest a fourth-order PT–APT symmetric quantization characterized by two EPs. Simultaneously, a third-order PT–APT quantization characterized by six EPs results from an enhanced dephasing rate. Finally, three dressing schemes (parallel, parallel-nested, and parallel-cascade) exhibit second-order quantization arising from weakest non-Hermitian interaction. These outcomes are used to develop quantum memory devices with enhanced sensitivity in the atomic system.
Non-Hermitian degeneracy, also known as exceptional point, has been recently seen as a new way to engineer the response of open physical systems. Based on natural non-Hermitian atomic coherence, we investigate spontaneous six-wave mixing (SSWM) and eight-wave mixing (SEWM) processes under both parity–time (PT) and anti-parity–time (anti-PT) symmetry, and we obtain high-dimensional coherent channels under third-order energy-level splitting. Finally, we reveal that the third-order non-Hermitian interaction between two dressing fields of the nested scheme is the strongest, and the parallel scheme is the weakest, with the cascade scheme considered intermediate between them. It can also be used to develop quantum memory devices with enhanced sensitivity in the atom-like system.