Abstract: Entanglement has been one of the dominant aspects distinguishing quantum theory from its classical counterpart. Indeed, entanglement has played a central role in recent developments in quantum technology, such as quantum computing, key distribution, etc. In order to use entanglement in these situations, a particular form is often needed, namely the maximal case. Various techniques have been used to manipulate entangled states, especially between distant parties. Generating long-distance entanglement from multiple shorter states has been studied, and it has been shown that there exists a class of states that can achieve optimal entanglement resources. In this paper, the particular class of states that yields the weakest link is numerically examined. The findings reveal that the range of this class is limited but substantial. Keywords: Quantum entanglement, Numerical methods, Maximal states.
Abstract: Entanglement has been one of the dominant aspects distinguishing quantum theory from its classical counterpart. Indeed, entanglement has played a central role in recent developments in quantum technology, such as quantum computing, key distribution, etc. In order to use entanglement in these situations, a particular form is often needed, namely the maximal case. Various techniques have been used to manipulate entangled states, especially between distant parties. Generating long-distance entanglement from multiple shorter states has been studied, and it has been shown that there exists a class of states that can achieve optimal entanglement resources. In this paper, the particular class of states that yields the weakest link is numerically examined. The findings reveal that the range of this class is limited but substantial. Keywords: Quantum entanglement, Numerical methods, Maximal states.
Entanglement has recently been one of the most essential elements in the development of various quantum technologies. In fact, a swapping protocol was introduced to create a long-distance entanglement from multiple shorter ones. Extending the previous work, this paper provides a more detailed numerical analysis to help create long-distance entanglement out of the two non-maximal three-level states. Specifically, it shows that while the protocol does not always yield optimal results, namely, the weaker link, there is a substantial number of states that yield an optimal result. Moreover, we discuss the numerical approach in showing the existence of states that provide a result close to the optimal outcome, which may be useful in realizing the long-distance entanglement used in quantum technology.
The quantum information network is important in establishing next-generation technology. In particular, maximal and long-distance entangled states are important in realizing a number of quantum information technologies, such as teleportation, key distribution and so forth. Entanglement swapping is a scheme that creates a long-distance network by using multiple short ones. Entanglement swapping protocols applied to non-maximal correlations have been thoroughly investigated by various people. Rather than providing any new analytic results, some examples of a numerical approach will be provided in this paper. In particular, the paper reveals the existence of different classes of coefficients that approximate the optimal outcome ( i.e. , the weaker average maximal entanglement between the two initial states). The new class of states is non-trivial in the sense that their coefficients are just as widely distributed as the coefficients of states satisfying optimality conditions are. Moreover, we will numerically examine entanglement swapping methods and show the distribution of optimal and general coefficients for three and four 2-level correlations.
The subjectivity seen in quantum theory has been the topic of major debate ever since the theory was first introduced about a century ago. The idea of treating the subject and the object independently has been difficult to accept in the science community; however, the subjective limit of knowledge has been discussed in philosophy for centuries. On the other hand, one of the important outcomes of recent studies of quantum theory is developing useful and practical applications from often controversial and philosophical debates such as the simultaneous existence of multiple states or superluminal influencing, which appears to violate the locality imposed by relativity. Establishing a long-distance correlation may be effective in a number of applications in quantum information technology. In this paper, an entanglement swapping scheme for three 2-level states is examined using numerical methods. In particular, it is studied that there is a class of non-maximal states that approximate the optimal outcome, namely, the weakest link.
Recent successes in quantum technology have provided a number of powerful tools for viewing nature in terms of information. In particular, quantum information science has proved to be a useful way to greatly simplify the way the universe is viewed as well as treating the subject, an observer, and the object, the observed universe, on an equal footing. Several important applications in quantum technology such as communication, information processing, etc., use a distinctive property of entanglement. In this article, a numerical simulation is applied to a swapping measurement protocol involving two 3-level entangled states. A different condition, in non-maximal states, that approximates the optimal result (i.e., the weaker link between the two initial states) will be shown through a numerical method. This different class of states is distributed just as wide as the class yielding the optimal result. The result may be useful in establishing a long distance maximal entanglement that is often fragile and unstable due to noise.
Building large-scale quantum computers, essential to demonstrating quantum advantage, is a key challenge. Quantum networks can help address this challenge by enabling the construction of large, robust, and more capable quantum computing platforms by connecting smaller quantum computers. Moreover, unlike classical systems, quantum networks can enable fully secured long-distance communication. Thus, quantum networks lie at the heart of the success of future quantum information technologies. In quantum networks, multipartite entangled states distributed over the network help implement and support many quantum network applications for communications, sensing, and computing. Our work focuses on developing optimal techniques to generate and distribute multipartite entanglement states efficiently. Prior works on generating general multipartite entanglement states have focused on the objective of minimizing the number of maximally entangled pairs while ignoring the heterogeneity of the network nodes and links as well as the stochastic nature of underlying processes. In this work, we develop a hypergraph-based linear programming framework that delivers optimal (under certain assumptions) generation schemes for general multipartite entanglement represented by graph states, under the network resources, decoherence, and fidelity constraints, while considering the stochasticity of the underlying processes. We illustrate our technique by developing generation schemes for the special cases of path and tree graph states and discuss optimized generation schemes for more general classes of graph states. Using extensive simulations over a quantum network simulator, we demonstrate the effectiveness of our developed techniques and show that they outperform prior known schemes by up to orders of magnitude.
Quantum entanglement plays a central role in many quantum communication protocols. It allows distant particles to share correlations beyond the limits of classical interactions. Entanglement is essential for superdense coding, quantum teleportation, and secure cryptographic key distribution in quantum communication. It is also a pillar for developing quantum networks, where the management and distribution of entanglement are crucial for connecting distant nodes. Although perfect entanglement is a sought-after ideal, experimental imperatives, including entanglement distribution over long distances, often limit the quality of entangled states. An important question is whether weaker entanglement still offers advantages. First, we study more general tasks than dense coding to show that simpler measurements, combined with entanglement, allow advantageous and sometimes even optimal qubit communication protocols to be obtained. We also demonstrate that simple measurements can generate quantum correlations that cannot be modelled by two classical communication bits and can constitute an optimal protocol with quantum resources. We implement a novel Bell-type inequality tailored for certifying full network non-locality (FNN) to develop certification methods guaranteeing security on an entanglement-based network. Our experiment uses two pairs of polarised entangled photons in a network configuration with three nodes, briefly referred to as a bilocal network scenario. Finally, we show that weakly entangled states can improve communication over a qubit channel using only separate (local) measurements on isotropic non-steerable two-qubit states, without interference, of individual photons, across two communication tasks: secret sharing and its stochastic variant.