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Entanglement Activation in Multiphoton Distillation Networks

Yu-Ao Chen, Rui Zhang, Yue-Yang Fei, Zhenhuan Liu, Xingjian Zhang, Xu-Fei Yin, Yingqiu Mao, Li Li, Nai-Le Liu, Xiongfeng Ma, Jian-Wei Pan

Published Feb 2, 2024• 1 citation
Publisher

Abstract

Abstract In quantum networks, residual states remaining after information processing can be valuable resources. Efficiently recycling these states to extract resources such as genuine multipartite entanglement and Einstein-Podolsky-Rosen pairs is essential for optimizing network performance. Our work demonstrates a tripartite entanglement distillation scheme using an eight-photon quantum platform, showcasing entanglement activation phenomena unique to multipartite systems. We successfully generate a three-photon genuinely entangled state from two bi-separable states through local operations and classical communication, illustrating multipartite entanglement activation. Furthermore, we extend our scheme to generate a three-photon state capable of extracting Einstein-Podolsky-Rosen pairs from two initial states lacking this capability, revealing a new entanglement activation phenomenon. Our findings offer not only practical applications for quantum networks but also a deeper theoretical understanding of multipartite entanglement structures.

DOI
10.21203/rs.3.rs-3828402/v1

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Abstract In quantum networks, residual states remaining after information processing can be valuable resources. Efficiently recycling these states to extract resources such as genuine multipartite entanglement and Einstein-Podolsky-Rosen pairs is essential for optimizing network performance. Our work demonstrates a tripartite entanglement distillation scheme using an eight-photon quantum platform, showcasing entanglement activation phenomena unique to multipartite systems. We successfully generate a three-photon genuinely entangled state from two bi-separable states through local operations and classical communication, illustrating multipartite entanglement activation. Furthermore, we extend our scheme to generate a three-photon state capable of extracting Einstein-Podolsky-Rosen pairs from two initial states lacking this capability, revealing a new entanglement activation phenomenon. Our findings offer not only practical applications for quantum networks but also a deeper theoretical understanding of multipartite entanglement structures.
In quantum networks, after passing through noisy channels or information processing, residual states may lack sufficient entanglement for further tasks, yet they may retain hidden quantum resources that can be recycled. Efficiently recycling these states to extract entanglement resources, such as genuine multipartite entanglement or Einstein-Podolsky-Rosen pairs, is essential for optimizing network performance. Here, we develop a tripartite entanglement distillation scheme using an eight-photon quantum platform, demonstrating entanglement superactivation phenomena which are unique to multipartite systems. We successfully generate a three-photon genuinely entangled state from two biseparable states via local operations and classical communication, demonstrating superactivation of genuine multipartite entanglement. Furthermore, we extend our scheme to generate a three-photon state capable of extracting an Einstein-Podolsky-Rosen pair from two initial states lacking this capability, revealing a previously unobserved entanglement superactivation phenomenon. Our methods and findings offer not only practical applications for quantum networks, but also lead to a deeper understanding of multipartite entanglement structures.
A central concept in quantum information processing is genuine multipartite entanglement (GME), a type of correlation beyond biseparability, that is, correlations that cannot be explained by statistical mixtures of partially separable states. GME is relevant for characterizing and benchmarking complex quantum systems, and it is an important resource for applications such as quantum communication. Remarkably, it has been found that GME can be activated from multiple copies of biseparable quantum states, which do not possess GME individually. Here, we experimentally demonstrate unambiguous evidence of such GME activation from two copies of a biseparable three-qubit state in a trapped-ion quantum processor. These results not only challenge notions of quantum resources but also highlight the potential of using multiple copies of quantum states to achieve tasks beyond the capabilities of the individual copies.
Multipartite entangled states are a fundamental resource for a wide range of quantum information processing tasks. In particular, in quantum networks, it is essential for the parties involved to be able to verify if entanglement is present before they carry out a given distributed task. Here we design and experimentally demonstrate a protocol that allows any party in a network to check if a source is distributing a genuinely multipartite entangled state, even in the presence of untrusted parties. The protocol remains secure against dishonest behaviour of the source and other parties, including the use of system imperfections to their advantage. We demonstrate the verification protocol in a three- and four-party setting using polarization-entangled photons, highlighting its potential for realistic photonic quantum communication and networking applications.
Quantum steering is a critical resource for multiple parties in real networks. Due to its inherent properties, new steerable resources cannot be generated using only free operations, and reallocating Einstein-Podolsky-Rosen steering within networks of certain structures has significant challenges. Therefore, this paper proposes a distillation scheme that selects remaining three-qubit states with bipartite steering components and distills them to yield a state with purer steerability. Based on different construction of communication networks, our protocol combines scenario-specific distillation strategies to obtain high-fidelity steerable states using a low number of copies via distinct measurement operations. The results indicate that our scheme eliminates the need to reallocate new steering states, reduces the steerable resources required for distillation, and remains robust to measurement defects. Furthermore, we introduce a framework for determining the presence of bipartite steerable in three-qubit states.
Multipartite entanglement purification is revisited by using the Local operations and classical communications(LOCCs). We demonstrate our idea by considering the tripartite case, i.e. the purification of tripartite entanglement. We express the general tripartite entangled states in a special representation of total spin operators J1232J_{123}^{2}J1232​ and % J_{12}^{2} of tripartite system with eigenvalues 15/4 and 2 respectively. This basis is a \textit{genuine basis} because it consists of of all the genuine entangled states of tripartite system. Our protocol is a recurrence one, and only two copies of the initial mixed tripartite entangled states are needed in each round. It is shown that if the initial fidelity is larger than a threshold 0.4, the purification process will succeed.The yield of the current protocol is higher than the previous multipartite entanglement purification protocols. As a by-product, we can get a bipartite pure Bell state when the purification protocol fails for W state. Our protocol also shows that there may be some special kind of tripartite entanglement which belongs to neither W-type entanglement nor GHZ-type entanglement.
Sharing genuine multipartite entanglement by considering collective use of copies of biseparable states, which are entangled across all bipartitions but lack genuine multipartite entanglement at the single-copy level, plays a central role in several quantum information processing protocols, and has been referred as genuine multipartite entanglement activation. We present a protocol for three-qutrit systems showing that two copies of rank-two biseparable states, entangled across every bipartition, are sufficient to generate a genuinely multipartite entangled state with nonzero probability. This contrasts with the three-qubit scenario where many copies of biseparable states might be required for sharing genuine multipartite entanglement. We subsequently generalize our protocols to the case of an arbitrary number of parties. Interestingly, the proposed construction naturally leads to the activation of genuinely nonlocal correlations, yielding a result that is stronger than genuine multipartite entanglement activation alone.