Abstract Level-cascaded four-wave mixing systems with multimode quantum state squeezing are of great significance for non-Hermitian exceptional control. In this paper, based on non-Hermitian systems, we couple the energy level dressing to generate multimode quantum correlated beams. We have conducted an in-depth discussion on the quantum squeezing characteristics of the cascaded four-mode system. We use the gain squeezing matrix of the Hamiltonian matrix to introduce a pair of Einstein–Podolsky–Rosen (EPR) injections and two pairs of EPR injections at different positions in the cascaded four-mode system. We found several key phenomena: (1) In covariance squeezing, dual EPR injections not only disrupt the original squeezing strength but also produce varying numbers of Hamiltonians depending on injection location; (2) For intensity-difference squeezing, multiple coherent injections enhance squeezing coherence proportionally to injection count, while increased Hamiltonians strengthen intensity-difference correlations. Particularly noteworthy is the equivalence between single EPR injections and E 2 E 3 dual injections, as well as between position-B dual EPR injections and E 2 E 3 E 4 triple injections. The results establish that EPR injections exhibit superior intensity hierarchy compared to multiple coherent or Hamiltonian injections, with their configuration capable of actively modifying inter-mode hierarchical relationships.
Abstract Level-cascaded four-wave mixing systems with multimode quantum state squeezing are of great significance for non-Hermitian exceptional control. In this paper, based on non-Hermitian systems, we couple the energy level dressing to generate multimode quantum correlated beams. We have conducted an in-depth discussion on the quantum squeezing characteristics of the cascaded four-mode system. We use the gain squeezing matrix of the Hamiltonian matrix to introduce a pair of Einstein–Podolsky–Rosen (EPR) injections and two pairs of EPR injections at different positions in the cascaded four-mode system. We found several key phenomena: (1) In covariance squeezing, dual EPR injections not only disrupt the original squeezing strength but also produce varying numbers of Hamiltonians depending on injection location; (2) For intensity-difference squeezing, multiple coherent injections enhance squeezing coherence proportionally to injection count, while increased Hamiltonians strengthen intensity-difference correlations. Particularly noteworthy is the equivalence between single EPR injections and E 2 E 3 dual injections, as well as between position-B dual EPR injections and E 2 E 3 E 4 triple injections. The results establish that EPR injections exhibit superior intensity hierarchy compared to multiple coherent or Hamiltonian injections, with their configuration capable of actively modifying inter-mode hierarchical relationships.
Einstein–Podolsky–Rosen (EPR) steering is a type of directional quantum correlation that holds immense significance and broad applications in quantum information processing. While EPR steering has been achieved across various physical systems, research into its implementation in non-Hermitian systems remains in its early stages. In this study, we delve into the realm of non-Hermitian control of EPR steering by leveraging atomic coherence-controlled energy-level cascaded four-wave mixing (ELC-FWM) processes. We derive analytical expressions for the generation of EPR steering within such non-Hermitian nonlinear systems, demonstrating that exceptional points (EPs) and multimode EPR steering can be realized through introducing dressing-control fields. Furthermore, we illustrate that nonlinear coherent channels and the associated steerability distribution of the output modes can be tailored during the EPR steering generation process, which is directly linked to the eigenvalues of non-Hermitian processes. Additionally, we analyze the impact of loss effects on generated multimode EPR steering. Our findings suggest that non-Hermitian control offers a promising all-optical approach for constructing practical quantum networks.
In recent years, multi-mode quantum entanglement and quantum squeezing have gained significant research interest. This paper successfully realizes quantitative control over the characteristic of quantum entanglement produced by cascaded parametrically amplified four-wave mixing (PA-FWM) through adjusting the Rabi frequency and dephasing rate of dressing fields, in which PT and anti-PT symmetry breaking, respectively, induce distinct energy-level quantization and generate coherent multi-channels in the atomic transition of the natural non-Hermitian system. Further simulations of the Duan criterion, the PPT criterion, and quantum steering have been implemented to investigate the properties of generated multi-mode entanglement when employing schemes featuring EPR injection and degenerate FWM. The comparison reveals that EPR injection enhances the entanglement of the injected EPR mode while suppressing the entanglement of other modes. Distinctive schemes of degenerate FWM and two pairs of EPR injections would successfully transform two originally separate modes into a pair of entangled modes, exhibiting significant research value in quantum metrology and relevant applications.
Abstract We report the quantum correlated triple beams via cascaded four-wave mixing (CFWM) amplified in single hot atomic vapor. Experimentally, we show that strong quantum correlation of three light beams, among them any two’s quantum correlation is characterized by the maximum value of intensity-difference squeezing (IDS) about −7.8 ± 0.3 dB. We found there is IDS between two idler beams, because two pairs of Einstein–Podolsky–Rosen injections potentially exist in our system. Besides, CFWM can emit three-mode beams at three different frequencies, in which these beams can be well separated in the spatial domain. Moreover, much difference with other methods, the injecting probe field can manipulate the gain and IDS of output three-mode light beams, which is resulting from competition relationship between cascaded two four-wave mixing processes. More interestingly, Autler–Townes splitting of gain peaks of output signals due to dressing effect of pumping fields, will lead to the evolution of measured two- and three-mode IDS from single-mode to multi-mode at frequency domain. This result will provide a multimode quantum resource which can potentially realize multimode entanglement and quantum networks.
Abstract We report the control of the dressed state in three-mode optical entanglement in an N-type four-level system using two cascaded parametric amplification four-wave mixing steps inside an atom-like optical cavity and injected by thermal optical fields: a coherent field and the Einstein–Podolsky–Rosen field. First, cavity dressing results in Aulter–Towns-like (AT-like peak) anti-squeezing. And the three-cavity dressing interaction induces multi-AT-like peaks. Meanwhile, the cavity enhanced nonlinear gain results in one squeezing dip polariton. In addition, the coupling of three enhanced nonlinear gains brings about multi-dip squeezing. Second, as two nonlinear coefficients change, the nonlinear phase makes the squeezing profile (in phase, amplification) turn into an anti-squeezing profile due to nonlinear loss (out of phase, de-amplification). Finally, the squeezing profile can also be modified by field dressing (AT splitting, enhancement and suppression), and the squeezing degree is affected by injection fields. Thus, by judging the squeezing of three nonseparability criteria, we get three-mode optical entanglement.
Einstein-Podolsky-Rosen (EPR) steering, a distinct class of quantum correlation intermediate between entanglement and Bell nonlocality, exhibits unique asymmetry and directionality. EPR steering swapping, analogous to entanglement swapping, enables two initially independent particles to establish EPR steering correlations. Recent advances in all-optical entanglement and EPR steering swapping have overcome the limitation of mutual electro-optical conversions. However, for quantum information systems required in real-world applications, extending these capabilities to multimode regimes remains largely underexplored. Here, we propose an m -to- n multimode all-optical EPR steering swapping architecture based on energy-level-cascaded four-wave mixing processes. By harnessing fundamental light-atom interactions, we demonstrate scalable multimode EPR steering swapping and realize non-Hermitian control over dressing-induced coherent channels. Crucially, our multimode approach demonstrates distinctive, mode-dependent features of non-monotonicity and asymmetry, which are unattainable in conventional two-mode schemes. The flexible controllability afforded by such multimode quantum correlations also facilitates interfaces between non-Hermitian light-matter systems, paving the way for practical implementations of EPR steering and all-optical quantum networks.
Multimode quantum squeezing plays an essential role in the fields of quantum metrology and quantum information. In this paper, we first construct a three- and four-mode energy-level cascaded four-wave mixing system in a single 85 R b vapor, and then analyze the quantum properties of the produced states, including the covariance matrix and the intensity squeezing with 11 possible Hamiltonians. In addition, the dressing field is applied to modulate the nonlinear susceptibility and the multimode quantum states. Our scheme allows active modulation of the quantum states integrated within the generation step, without the need for any post-operation of the optics. The mode number of the states also can be extended using more pump fields and the dressing effect. Our study provides a promising candidate to generate multimode quantum states and multimode quantum squeezing within a quantum device involved in the construction of practical quantum networks.