scholarly journals EntangleNet: Theoretical Reestablishment of Entanglement in Quantum Networks †

2018 ◽  
Vol 8 (10) ◽  
pp. 1935
Author(s):  
Mihai-Zicu Mina ◽  
Pantelimon Popescu
Keyword(s):  
Reliable Method ◽  
Entanglement Swapping ◽  
Quantum States ◽  
Entangled State ◽  
Quantum Network ◽  
Quantum Networks ◽  
Maximally Entangled State ◽  
Highly Sensitive ◽  
The Subject ◽  
Entanglement Distribution

In the practical context of quantum networks, the most reliable method of transmitting quantum information is via teleportation because quantum states are highly sensitive. However, teleportation consumes a shared maximally entangled state. Two parties Alice and Bob located at separate nodes that wish to reestablish their shared entanglement will not send entangled qubits directly to achieve this goal, but rather employ a more efficient mechanism that ensures minimal time resources. In this paper, we present a quantum routing scheme that exploits entanglement swapping to reestablish consumed entanglement. It improves and generalizes previous work on the subject and reduces the entanglement distribution time by a factor of 4 k in an arbitrary scale quantum network, where N = 4 k - 1 is a required number of quantum nodes located between source and destination. In addition, k is the greatest positive integer considered by Alice or Bob, such that afterwards they choose N quantum switches.

scholarly journals Experimental creation of multi-photon high-dimensional layered quantum states

2020 ◽  
Vol 6 (1) ◽  
Author(s):  
Xiao-Min Hu ◽  
Wen-Bo Xing ◽  
Chao Zhang ◽  
Bi-Heng Liu ◽  
Matej Pivoluska ◽  
...  
Keyword(s):  
Quantum Information ◽  
Quantum Entanglement ◽  
Quantum State ◽  
Quantum States ◽  
High Dimensional ◽  
Entangled States ◽  
Entangled State ◽  
Quantum Network ◽  
Quantum Networks ◽  
Qubit States

Abstract Quantum entanglement is one of the most important resources in quantum information. In recent years, the research of quantum entanglement mainly focused on the increase in the number of entangled qubits or the high-dimensional entanglement of two particles. Compared with qubit states, multipartite high-dimensional entangled states have beneficial properties and are powerful for constructing quantum networks. However, there are few studies on multipartite high-dimensional quantum entanglement due to the difficulty of creating such states. In this paper, we experimentally prepared a multipartite high-dimensional state $$\left|{\Psi }_{442}\right\rangle =\frac{1}{2}(\left|000\right\rangle +\left|110\right\rangle +\left|221\right\rangle +\left|331\right\rangle )$$ Ψ 442 = 1 2 ( 000 + 110 + 221 + 331 ) by using the path mode of photons. We obtain the fidelity F = 0.854 ± 0.007 of the quantum state, which proves a real multipartite high-dimensional entangled state. Finally, we use this quantum state to demonstrate a layered quantum network in principle. Our work highlights another route toward complex quantum networks.

scholarly journals Optimal teleportation via noisy quantum channels without additional qubit resources

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Dong-Gil Im ◽  
Chung-Hyun Lee ◽  
Yosep Kim ◽  
Hyunchul Nha ◽  
M. S. Kim ◽  
...  
Keyword(s):  
Quantum Computing ◽  
Quantum Teleportation ◽  
Quantum Communication ◽  
Quantum Noise ◽  
Single Copy ◽  
Entangled State ◽  
Quantum Network ◽  
Quantum Channels ◽  
Maximally Entangled State ◽  
Near Term

AbstractQuantum teleportation exemplifies how the transmission of quantum information starkly differs from that of classical information and serves as a key protocol for quantum communication and quantum computing. While an ideal teleportation protocol requires noiseless quantum channels to share a pure maximally entangled state, the reality is that shared entanglement is often severely degraded due to various decoherence mechanisms. Although the quantum noise induced by the decoherence is indeed a major obstacle to realizing a near-term quantum network or processor with a limited number of qubits, the methodologies considered thus far to address this issue are resource-intensive. Here, we demonstrate a protocol that allows optimal quantum teleportation via noisy quantum channels without additional qubit resources. By analyzing teleportation in the framework of generalized quantum measurement, we optimize the teleportation protocol for noisy quantum channels. In particular, we experimentally demonstrate that our protocol enables to teleport an unknown qubit even via a single copy of an entangled state under strong decoherence that would otherwise preclude any quantum operation. Our work provides a useful methodology for practically coping with decoherence with a limited number of qubits and paves the way for realizing noisy intermediate-scale quantum computing and quantum communication.

The influence of excitation number of photon-added coherent state field on the entanglement swapping process

2017 ◽  
Vol 31 (27) ◽  
pp. 1750198 ◽  
Author(s):  
M. Soltani ◽  
M. K. Tavassoly ◽  
R. Pakniat
Keyword(s):  
Coherent State ◽  
Quantum Electrodynamics ◽  
Coherent States ◽  
Success Probability ◽  
Entanglement Swapping ◽  
Cavity Quantum Electrodynamics ◽  
Linear Entropy ◽  
Entangled State ◽  
Maximally Entangled State ◽  
Coherent Field

In this paper, we outline a scheme for the entanglement swapping procedure based on cavity quantum electrodynamics using the Jaynes–Cummings model consisting of the coherent and photon-added coherent states. In particular, utilizing the photon-added coherent states ([Formula: see text][Formula: see text][Formula: see text][Formula: see text], where [Formula: see text] is the Glauber coherent state) in the scheme, enables us to investigate the effect of [Formula: see text], i.e., the number of excitations corresponding to the photon-added coherent field on the entanglement swapping process. In the scheme, two two-level atoms [Formula: see text] and [Formula: see text] are initially entangled together, and distinctly two exploited cavity fields [Formula: see text] and [Formula: see text] are prepared in an entangled state (a combination of coherent and photon-added coherent states). Interacting the atom [Formula: see text] with field [Formula: see text] (via the Jaynes–Cummings model) and then making detection on them, transfers the entanglement from the two atoms [Formula: see text], [Formula: see text] and the two fields [Formula: see text], [Formula: see text] to the atom-field “[Formula: see text]-[Formula: see text]”, i.e., entanglement swapping occurs. In the continuation, we pay our attention to the evaluation of the fidelity of the swapped entangled state relative to a suitable maximally entangled state, success probability of the performed detections and linear entropy as the degree of entanglement of the swapped entangled state. It is demonstrated that, an increase in the number of excitations, [Formula: see text], leads to the increment of fidelity as well as the amount of entanglement. According to our numerical results, the maximum values of fidelity (linear entropy) 0.98 (0.46) is obtained for [Formula: see text], however, the maximum value of success probability does not significantly change by increasing [Formula: see text].

scholarly journals Policies for elementary links in a quantum network

Quantum ◽  
2021 ◽  
Vol 5 ◽  
pp. 537
Author(s):  
Sumeet Khatri
Keyword(s):  
Decision Process ◽  
Success Probability ◽  
Coherence Time ◽  
Decision Processes ◽  
Quantum Network ◽  
Quantum Networks ◽  
Fundamental Limitations ◽  
Process Framework ◽  
Entanglement Distribution ◽  
Near Term

Distributing entanglement over long distances is one of the central tasks in quantum networks. An important problem, especially for near-term quantum networks, is to develop optimal entanglement distribution protocols that take into account the limitations of current and near-term hardware, such as quantum memories with limited coherence time. We address this problem by initiating the study of quantum network protocols for entanglement distribution using the theory of decision processes, such that optimal protocols (referred to as policies in the context of decision processes) can be found using dynamic programming or reinforcement learning algorithms. As a first step, in this work we focus exclusively on the elementary link level. We start by defining a quantum decision process for elementary links, along with figures of merit for evaluating policies. We then provide two algorithms for determining policies, one of which we prove to be optimal (with respect to fidelity and success probability) among all policies. Then we show that the previously-studied memory-cutoff protocol can be phrased as a policy within our decision process framework, allowing us to obtain several new fundamental results about it. The conceptual developments and results of this work pave the way for the systematic study of the fundamental limitations of near-term quantum networks, and the requirements for physically realizing them.

PERFECT TELEPORTATION OF UNKNOWN QUDIT BY A d-LEVEL GHZ CHANNEL

2009 ◽  
Vol 07 (04) ◽  
pp. 755-770 ◽  
Author(s):  
YINXIANG LONG ◽  
DAOWEN QIU ◽  
DONGYANG LONG
Keyword(s):  
General Scheme ◽  
Bell State ◽  
Ghz State ◽  
Quantum States ◽  
Entangled State ◽  
Input State ◽  
Quantum Channels ◽  
Maximally Entangled State ◽  
Ghz States ◽  
Measurement Basis

In the past decades, various schemes of teleportation of quantum states through different types of quantum channels (a prior shared entangled state between the sender and the receiver), e.g. EPR pairs, generalized Bell states, qubit GHZ states, standard W states and its variations, genuine multiqubit entanglement states, etc., have been developed. Recently, three-qutrit quantum states and two-qudit quantum states have also been considered as quantum channels for teleportation. In this paper, we investigate the teleportation of an unknown qudit using a d level GHZ state, i.e. a three-qudit maximally entangled state, as quantum channel. We design a general scheme of faithful teleportation of an unknown qudit using a d-level GHZ state shared between the sender and the receiver, or among the sender, the receiver and the controller; an unknown two-qudit of Schmidt form using a d level GHZ state shared between the sender and the receiver; as well as an unknown arbitrary two-qudit using two shared d level GHZ states between the sender, the receiver and the controller, or using one shared d level GHZ state and one shared generalized Bell state. We obtain the general formulas of Alice's measurement basis, Charlie's measurement basis and Bob's unitary operations to recover the input state of Alice. It is intuitionistic to generalize the protocols of teleporting an arbitrary two-qudit state to teleporting an arbitrary n-qudit state.

scholarly journals A Practical Quantum Network Coding Protocol Based on Non-Maximally Entangled State

2021 ◽  
Vol 68 (2) ◽  
pp. 2651-2663
Author(s):  
Zhen-Zhen Li ◽  
Zi-Chen Li ◽  
Xiu-Bo Chen ◽  
Zhiguo Qu ◽  
Xiaojun Wang ◽  
...  
Keyword(s):  
Network Coding ◽  
Entangled State ◽  
Quantum Network ◽  
Maximally Entangled State ◽  
Quantum Network Coding

scholarly journals Percolation Distribution in Small-World Quantum Networks

2022 ◽  
Vol 12 (2) ◽  
pp. 701
Author(s):  
Jianxiong Liang ◽  
Xiaoguang Chen ◽  
Tianyi Wang
Keyword(s):  
Percolation Threshold ◽  
Network Structure ◽  
Percolation Theory ◽  
Small World ◽  
Entanglement Swapping ◽  
Quantum Networks ◽  
Communication Links ◽  
Network Topologies ◽  
Entanglement Distribution ◽  
Percolation Thresholds

Quantum networks have good prospects for applications in the future. Compared with classical networks, small-world quantum networks have some interesting properties. The topology of the network can be changed through entanglement exchange operations, and different network topologies will result in different percolation thresholds when performing entanglement percolation. A lower percolation threshold means that quantum networks require fewer minimum resources for communication. Since a shared singlet between two nodes can still be a limitation, concurrency percolation theory (ConPT) can be used to relax the condition. In this paper, we investigate how entanglement distribution is performed in small-world quantum networks to ensure that nodes in the network can communicate with each other by establishing communication links through entanglement swapping. Any node can perform entanglement swapping on only part of the connected edges, which can reduce the influence of each node in the network during entanglement swapping. In addition, the ConPT method is used to reduce the percolation threshold even further, thus obtaining a better network structure and reducing the resources required.

Deterministic bidirectional quantum-controlled teleportation with six-qubit maximally entangled state

2019 ◽  
Vol 34 (35) ◽  
pp. 1950290 ◽  
Author(s):  
Wanbin Zhang
Keyword(s):  
Quantum Channel ◽  
Controlled Teleportation ◽  
Entangled State ◽  
Quantum Network ◽  
Maximally Entangled State ◽  
Bidirectional Quantum Controlled Teleportation ◽  
The Given

Each of three nodes in a quantum network has two qubits. The total six qubits are in a maximally entangled state [Helwig et al., Phys. Rev. A 86, 052335 (2012)]. Using such an entangled state as quantum channel, we put forward three deterministic bidirectional quantum-controlled teleportation (BQCT) schemes. To be specific, BQCT can be realized between any two nodes in a deterministic manner with another as the control. Alternatively, the BQCT capacity of such state in the given qubit distribution is thus essentially revealed by virtue of the schemes.

scholarly journals A SUFFICIENT AND NECESSARY CONDITION FOR SUPERDENSE CODING OF QUANTUM STATES

2008 ◽  
Vol 06 (05) ◽  
pp. 1115-1125 ◽  
Author(s):  
DAOWEN QIU
Keyword(s):  
Lower Bound ◽  
Success Probability ◽  
Quantum States ◽  
Entangled States ◽  
Necessary Condition ◽  
Entangled State ◽  
Maximally Entangled State ◽  
High Success Probability ◽  
Sufficient And Necessary Condition ◽  
Arbitrary Quantum

Recently, Harrow et al. [Phys. Rev. Lett.92 (2004) 187901] gave a method for preparing an arbitrary quantum state with high success probability by physically transmitting some qubits, and by consuming a maximally entangled state, together with exhausting some shared random bits. In this paper, we discover that some states are impossible to be perfectly prepared by Alice and Bob initially sharing some entangled states. In particular, we present a sufficient and necessary condition for the states being enabled to be exactly prepared with probability equal to unity, in terms of the initial entangled states (maybe nonmaximally). In contrast, if the initially shared entanglement is maximal, then the probabilities for preparing these quantum states are smaller than unity. Furthermore, the lower bound on the probability for preparing some states are derived.

Four-agent bidirectional quantum controlled teleportation via quantum entanglement swapping

2021 ◽  
pp. 2150073
Author(s):  
Wanbin Zhang ◽  
Baosheng Li
Keyword(s):  
Quantum Entanglement ◽  
Quantum Channel ◽  
Entanglement Swapping ◽  
Controlled Teleportation ◽  
Entangled State ◽  
Long Distance ◽  
Maximally Entangled State ◽  
Distance Communication ◽  
Bidirectional Quantum Controlled Teleportation ◽  
The Given

A total of seven qubits are in a maximally entangled state. Using such an entangled state as quantum channel is based on the construction requirements of quantum long-distance communication [Pan et al., Nature 488, 185 (2012)]. Multi-party quantum channel (QC) should be studied. We put forward three deterministic bidirectional quantum controlled teleportation (BQCT) schemes. To be specific, BQCT can be realized between any two parties in a deterministic manner with another as the control. Alternatively, the BQCT capacity of such state in the given qubit distribution is thus essentially revealed by virtue of the schemes.

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