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arXiv:2602.07788

Quantum Steering and Entanglement in a Tritter: Hierarchy under Loss

Jifeng Sun, Shumin Yang, Teng Zhao, Qingqian Kang, Liyun Hu

quant-phSubmitted Feb 8, 2026• Announced Feb 10, 2026• 0 citations
v1 · Feb 8, 2026v2 · Aug 3, 2026
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Abstract

Multipartite entangled states of continuous variables are fundamental resources for scalable quantum information processing. We study the correlation hierarchy in a tripartite state engineered by mixing a two-mode squeezed vacuum with a coherent state on a tritter, a key linear optical element for multimode state generation. Using the covariance matrix formalism, we comprehensively analyze the entanglement and Einstein-Podolsky-Rosen (EPR) steering among the output modes. The strength of both correlations is governed solely by the squeezing parameter and is independent of the coherent amplitude. We further examine the impact of inevitable optical losses in various channel configurations. The results show that while losses degrade correlations, EPR steering remains monogamous and exhibits stricter resilience thresholds than entanglement. Our analysis, supported by parameter extension techniques, confirms that the steering condition is more stringent than the inseparability criterion, clearly demonstrating that steering forms a strict subset of entanglement. These results elucidate the correlation structure in a readily generated multimode state and offer practical insights for developing asymmetric quantum protocols, such as one-sided device-independent tasks, where EPR steering serves as a critical resource.

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Multipartite entangled states of continuous variables are fundamental resources for scalable quantum information processing. We study the correlation hierarchy in a tripartite state engineered by mixing a two-mode squeezed vacuum with a coherent state on a tritter, a key linear optical element for multimode state generation. Using the covariance matrix formalism, we comprehensively analyze the entanglement and Einstein-Podolsky-Rosen (EPR) steering among the output modes. The strength of both correlations is governed solely by the squeezing parameter and is independent of the coherent amplitude. We further examine the impact of inevitable optical losses in various channel configurations. The results show that while losses degrade correlations, EPR steering remains monogamous and exhibits stricter resilience thresholds than entanglement. Our analysis, supported by parameter extension techniques, confirms that the steering condition is more stringent than the inseparability criterion, clearly demonstrating that steering forms a strict subset of entanglement. These results elucidate the correlation structure in a readily generated multimode state and offer practical insights for developing asymmetric quantum protocols, such as one-sided device-independent tasks, where EPR steering serves as a critical resource.
Einstein-Podolsky-Rosen (EPR) steering exhibits an inherent asymmetric feature that differs from both entanglement and Bell nonlocality, which leads to one-way EPR steering. Although this one-way EPR steering phenomenon has been experimentally observed, the schemes to manipulate the direction of EPR steering have not been investigated thoroughly. In this paper, we propose and experimentally demonstrate three schemes to manipulate the direction of EPR steering, either by varying the noise on one party of a two-mode squeezed state (TMSS) or transmitting the TMSS in a noisy channel. The dependence of the direction of EPR steering on the noise and transmission efficiency in the quantum channel is analyzed. The experimental results show that the direction of EPR steering of the TMSS can be changed in the presented schemes. Our work is helpful in understanding the fundamental asymmetry of quantum nonlocality and has potential applications in future asymmetric quantum information processing.
Einstein-Podolsky-Rosen (EPR) steering, a distinctive quantum correlation, reveals a unique and inherent asymmetry. This research delves into the multifaceted asymmetry of EPR steering within high-dimensional quantum systems, exploring both theoretical frameworks and experimental validations. We introduce the concept of genuine high-dimensional one-way steering, wherein a high Schmidt number of bipartite quantum states is demonstrable in one steering direction but not reciprocally. Additionally, we explore two criteria to certify the lower and upper bounds of the Schmidt number within a one-sided device-independent context. These criteria serve as tools for identifying potential asymmetric dimensionality of EPR steering in both directions. By preparing two-qutrit mixed states with high fidelity, we experimentally observe asymmetric structures of EPR steering in the C^{3}⊗C^{3} Hilbert space. Our Letter offers new perspectives to understand the asymmetric EPR steering beyond qubits and has potential applications in asymmetric high-dimensional quantum information tasks.
Using Venn diagrams, we classify the different types of two-mode Gaussian continuous variable quantum correlation including directional entanglement and Einstein-Podolsky-Rosen (EPR) steering. We establish unified signatures for one- and two-way quantum steering, entanglement, and discord beyond entanglement in terms of an EPR-type variance. By focusing on Gaussian states, we link an optimized condition for entanglement based on an EPR variance to the Simon-Peres condition. This allows us to quantify the asymmetry of the Gaussian entanglement, and to relate the asymmetry to a directional quantum teleportation protocol where Alice and Bob possess asymmetrically noisy channels. Our analysis enables a determination of the type and direction of quantum correlation in a way that is easily measured in experiment. We also find that for symmetric states, when discord exceeds a certain threshold, the states are necessarily steerable.
Abstract Einstein–Podolsky–Rosen (EPR) steering is a useful resource for secure quantum information tasks. It is crucial to investigate the effect of inevitable loss and noise in quantum channels on EPR steering. We analyze and experimentally demonstrate the influence of purity of quantum states and excess noise on Gaussian EPR steering by distributing a two-mode squeezed state through lossy and noisy channels, respectively. We show that the impurity of state never leads to sudden death of Gaussian EPR steering, but the noise in quantum channel can. Then we revive the disappeared Gaussian EPR steering by establishing a correlated noisy channel. Different from entanglement, the sudden death and revival of Gaussian EPR steering are directional. Our result confirms that EPR steering criteria proposed by Reid and I. Kogias et al. are equivalent in our case. The presented results pave way for asymmetric quantum information processing exploiting Gaussian EPR steering in noisy environment.
In this work, we propose an asymmetric multi-user access optical network with hierarchical structure in terms of steering ability. The N-partite system is generated by mixing two squeezed lights and N−2 vacuum modes at N−1 beam splitters. The asymmetry of this system can be constructed by choosing proper reflectivities of beam splitters and introducing asymmetric loss to channels of the network, such that the steering ability is distributed asymmetrically among users. By proper construction, one superior in the network possesses higher steering ability than any one of the remaining N−1 subordinates. We show how to accomplish the directional quantum steering between them, i.e., the superior can apparently steer any subordinate’s state, but it cannot always happen in the opposite direction. In addition, we quantify the thresholds of loss tolerance that will prevent the extraction of information of the superior by M(1≤M≤N−1) subordinates’ local measurements. An important feature of such a network is that the superior can send a secret message to certain subordinates without trustworthy assumptions about them and their apparatus. Our findings have applications in one-sided device-independent quantum communication protocol with multi-users.
Quantum steering is a stronger form of quantum entanglement and is considered to rigorously address the nonlocal correlation in the original Einstein–Podolsky–Rosen paradox. We study the quantum steerability of two classes of continuous-variable (CV) entangled states that are most often employed for CV quantum informatics-entangled coherent states (ECSs) and two-mode-squeezed vacuum (TMSV). We test the two steering criteria by utilizing Heisenberg and entropic uncertainty relations, respectively, and find that the latter can reveal the steerability of ECSs of any size and parity, whereas the former scarcely can. The steering behaviors of the two states are investigated and compared when they experience a noisy environment, i.e., an amplitude damping channel. When the noise is added asymmetrically, e.g., when only one party of the bipartite system is subject to noise, quantum steering can be possible only in one direction, e.g., Alice on Bob’s state but not Bob on Alice’s state. We show the emergence of this one-directional steering for both ECSs and the TMSV in a certain parameter range under decoherence.