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Frontiers of Physics

Evaluation of continuous variable controlled quantum teleportation through quantum nonlocality

Yuehan Tian, Nengfei Gong, Yining Li, Tiejun Wang

Published Jan 1, 2026• 0 citations
Publisher

Abstract

Quantum nonlocality is an important resource for ensuring the security of quantum communication, which plays an indispensable role in building quantum networks. From bipartite to multipartite quantum systems, various inequalities are constructed as tools to unearth the quantum nonlocality. Control power is a crucial indicator for evaluating supervision, control, and collaboration in quantum networks. However, there is currently no exploration of the relevance between the control power and the quantum nonlocality in continuous variable quantum networks. In this work, based on the Mermin−Klyshko (MK) inequality with rotated quantum-number parity operators, we reveal the quantum nonlocality of general Greenberger−Horne−Zeilinger-type (GHZ-type) entangled coherent states, which can be extended to arbitrary multi-mode states. And then, we evaluate the control power through quantum nonlocality in continuous variable controlled quantum teleportation via a 3-mode GHZ-type entangled coherent state as channel. The results show that the control power of continuous variable quantum networks is a monotonically increasing function of genuine tripartite nonlocality. This quantitative dependence of control power on quantum nonlocality remains robust even with decoherence. The advantages of the MK inequality are simplicity in computation and scalability into arbitrary multi-mode channels. In addition, maximal violation of the MK inequality can be achieved more easily in the experiment. Our work proves that, compared with the Bell−Mermin inequality, the MK inequality performs better in experimental measurements of complete control power; compared with the Svetlichny inequality, the MK inequality avoids negative and unreasonable control power when inequalities exceed the classical upper bound. Therefore, the MK inequality is found to be a more reliable tool to reveal the quantum nonlocality in multipartite systems. This work illuminates the important application of nonlocality in multipartite continuous variable quantum communications and is of significance for the construction of practical quantum protocols.

DOI
10.15302/frontphys.2026.083203

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Quantum nonlocality is an important resource for ensuring the security of quantum communication, which plays an indispensable role in building quantum networks. From bipartite to multipartite quantum systems, various inequalities are constructed as tools to unearth the quantum nonlocality. Control power is a crucial indicator for evaluating supervision, control, and collaboration in quantum networks. However, there is currently no exploration of the relevance between the control power and the quantum nonlocality in continuous variable quantum networks. In this work, based on the Mermin−Klyshko (MK) inequality with rotated quantum-number parity operators, we reveal the quantum nonlocality of general Greenberger−Horne−Zeilinger-type (GHZ-type) entangled coherent states, which can be extended to arbitrary multi-mode states. And then, we evaluate the control power through quantum nonlocality in continuous variable controlled quantum teleportation via a 3-mode GHZ-type entangled coherent state as channel. The results show that the control power of continuous variable quantum networks is a monotonically increasing function of genuine tripartite nonlocality. This quantitative dependence of control power on quantum nonlocality remains robust even with decoherence. The advantages of the MK inequality are simplicity in computation and scalability into arbitrary multi-mode channels. In addition, maximal violation of the MK inequality can be achieved more easily in the experiment. Our work proves that, compared with the Bell−Mermin inequality, the MK inequality performs better in experimental measurements of complete control power; compared with the Svetlichny inequality, the MK inequality avoids negative and unreasonable control power when inequalities exceed the classical upper bound. Therefore, the MK inequality is found to be a more reliable tool to reveal the quantum nonlocality in multipartite systems. This work illuminates the important application of nonlocality in multipartite continuous variable quantum communications and is of significance for the construction of practical quantum protocols.
Controlled quantum teleportation is an important extension of multipartite quantum teleportation, which plays an indispensable role in building quantum networks. Compared with discrete variable counterparts, continuous variable controlled quantum teleportation can generate entanglement deterministically and exhibit higher superiority of the supervisor's authority. Here, we define a measure to quantify the control power in continuous variable controlled quantum teleportation via Greenberger-Horne-Zeilinger-type entangled coherent state channels. Our results show that control power in continuous variable controlled quantum teleportation increases with the mean photon number of coherent states. Its upper bound is 1/2, which exceeds the upper bound in discrete variable controlled quantum teleportation (1/3). The robustness of the protocol is analyzed with photon absorption. The results show that the improving ability of the control power will descend by the increasing photon loss, with the upper bound unchanged and robust. Our results illuminate the role of control power in multipartite continuous variable quantum information processing and provide a criterion for evaluating the quality of quantum communication networks.
We study how conditional photon operations can affect multipartite quantum correlations, specifically nonlocality and entanglement, of the continuous-variable Greenberger-Horne-Zeilinger (GHZ) states. We find that the violation of the Mermin-Klyshko inequality revealing the multipartite nonlocality can be made stronger with photon subtraction applied on each mode of the original GHZ states, particularly in a weak squeezing regime. Photon addition applied on local modes also turns out to enhance the degree of multipartite nonlocality in a broad range of parameters. We further investigate the effects of the photon operations on the degree of multipartite entanglement by looking into the Gaussian tangle, the fidelity of teleportation network, and the quadrature correlations. We find that photon subtraction applied on two modes enhances those entanglement characteristics in a practical squeezing regime while there is no improvement made by photon addition.
Multipartite quantum nonlocality is an important diagnostic tool and resource for both researches in fundamental quantum mechanics and applications in quantum information protocols. Shared reference frames among all parties are usually required for experimentally observing quantum nonlocality, which is not possible in many circumstances. Previous results have shown violations of bipartite Bell inequalities with approaching unit probability, without shared reference frames. Here we experimentally demonstrate genuine multipartite quantum nonlocality without shared reference frames, using the Svetlichny inequality. A significant violation probability of 0.58 is observed with a high-fidelity three-photon Greenberger-Horne-Zeilinger state. Furthermore, when there is one shared axis among all the parties, which is the usual case in fiber-optic or earth-satellite links, the experimental results demonstrate the genuine three-partite nonlocality with certainty. Our experiment will be helpful for applications in multipartite quantum communication protocols.
Controlled quantum gate teleportation (CQGT) enables controller-regulated quantum gate transmission in distributed networks. The current CQGT scheme faces security challenges as both genuine tripartite entanglement and insecure classical-quantum hybrid resources can achieve high standard metrics (fidelity or control power). In this paper, we propose a device-independent (DI) CQGT verification scheme using genuine tripartite nonlocality in black-box scenarios. In the quantum cnot gate teleportation, our DI verification scheme based on Svetlichny inequality achieved the maximum inequality violation, which is superior to the traditional Clauser-Horne-Shimony-Holt (CHSH) type scheme. It is crucial that we establish a direct relationship between Svetlichny inequality violation and the effective control power (ECP) of the controller in eavesdropping depolarization channels, where ECP corresponds to the maximum inequality violation. This work addresses critical security verification gaps in CQGT protocols while highlighting the fundamental role of multipartite nonlocality in quantum information processing.
According to the studies of genuine tripartite nonlocality in discrete variable quantum systems conducted so far, Svetlichny inequality is considered as the best Bell-type inequality to detect genuine (three way) nonlocality of pure tripartite genuine entangled states. In the present work, we have considered another Bell-type inequality (which has been reported as the 99th facet of NS 2 local polytope in Bancal et al (2013 Phys. Rev. A 88 014102 ), to reveal genuine tripartite nonlocality of generalized GHZ (Greenberger–Horne–Zeilinger) class and a subclass of extended GHZ class states Acín et al (2000 Phys. Rev. Lett. 85 1560 ) thereby proving the conjecture given by Bancal et al (2013 Phys. Rev. A 88 014102 ) for the GGHZ class and the subclass of extended GHZ states. We compare the violation of this inequality with Svetlichny inequality which reveals the efficiency of the former inequality over the latter to demonstrate genuine nonlocality using the above classes of quantum states. Even in some cases discord monogamy score can be used as a better measure of quantum correlation over Svetlichny inequality for those classes of pure states. Besides, the 99th facet inequality is found efficient not only for revealing genuine nonlocal behavior of correlations emerging in systems using pure entangled states but also in some cases of mixed entangled states over Svetlichny inequality and some well known measures of entanglement.
Teleporting an unknown qubit state is a paradigmatic quantum information processing task revealing the advantage of quantum communication protocols over their classical counterpart. For a teleportation protocol using a Bell state as quantum channel, the resource has been identified to be the concurrence. However, for mixed multipartite states the lack of computable entanglement measures has made the identification of the quantum resource responsible for this advantage more challenging. Here, by building on previous results showing that localizable concurrence is the necessary resource for controlled quantum teleportation, we show that any teleportation protocol using an arbitrary multipartite state, that includes a Bell measurement, requires a nonvanishing localizable concurrence between two of its parties to perform better than the classical protocol. By first analyzing Greenberger–Horne–Zeilinger (GHZ) channel and GHZ measurement teleportation protocol, in the presence of GHZ-symmetric-preserving noise, we compare different multipartite entanglement measures with the fidelity of teleportation, and we find that the protocol performs better than the classical protocol when all multipartite entanglement measures vanish, except for the localizable concurrence. Finally, we extend our proof to an arbitrary teleportation protocol with an arbitrary multipartite entangled channel.