scholarly journals Graph Picture of Linear Quantum Networks and Entanglement

Quantum ◽  
2021 ◽  
Vol 5 ◽  
pp. 611
Author(s):  
Seungbeom Chin ◽  
Yong-Su Kim ◽  
Sangmin Lee
Keyword(s):  
Perfect Matching ◽  
Entangled States ◽  
Entangled State ◽  
Quantum Networks ◽  
Entanglement Generation ◽  
Essential Information ◽  
Quantum Particles ◽  
Number Increase ◽  
Mapping Process ◽  
Linear Quantum

The indistinguishability of quantum particles is widely used as a resource for the generation of entanglement. Linear quantum networks (LQNs), in which identical particles linearly evolve to arrive at multimode detectors, exploit the indistinguishability to generate various multipartite entangled states by the proper control of transformation operators. However, it is challenging to devise a suitable LQN that carries a specific entangled state or compute the possible entangled state in a given LQN as the particle and mode number increase. This research presents a mapping process of arbitrary LQNs to graphs, which provides a powerful tool for analyzing and designing LQNs to generate multipartite entanglement. We also introduce the perfect matching diagram (PM diagram), which is a refined directed graph that includes all the essential information on the entanglement generation by an LQN. The PM diagram furnishes rigorous criteria for the entanglement of an LQN and solid guidelines for designing suitable LQNs for the genuine entanglement. Based on the structure of PM diagrams, we compose LQNs for fundamental N-partite genuinely entangled states.

Practical one-step synthesis of multipartite entangled states on superconducting circuits

2019 ◽  
Vol 17 (07) ◽  
pp. 1950051
Author(s):  
Rui Tao ◽  
Xiao-Tao Mo ◽  
Zheng-Yuan Xue ◽  
Jian Zhou
Keyword(s):  
Quantum Information Processing ◽  
Single Step ◽  
Entangled States ◽  
Entangled State ◽  
Many Body ◽  
Entanglement Generation ◽  
Superconducting Circuits ◽  
Transmission Line Resonator ◽  
One Step ◽  
Microwave Control

Quantum entanglement is an important resource for quantum information processing tasks. However, realistic multipartite entangled state production is very difficult. In this paper, we propose an efficient single-step scheme for generating many body Greenberger–Horne–Zeilinger (GHZ) states on superconducting circuits by using a superconducting transmission-line resonator (TLR) interact with [Formula: see text] superconducting transmon qubits. The distinct merit of our proposal is that it does not require the qubit-resonator coupling strengths to be the same, which is usually impractical experimentally, and thus is one of the main reasons for entanglement generation infidelity in previous single-step schemes. The removing of the uniform interaction requirement is achieved by modulating the qubits splitting frequencies with ac microwave fields, which results in tunable individual qubit-resonator coupling strength, and thus effective uniform qubit–qubit interaction Hamiltonian can be obtained. Since microwave control is conventional nowadays, our proposal can be directly tested experimentally, which makes previous multipartite entangled states generation schemes more efficient.

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 Path identity as a source of high-dimensional entanglement

2020 ◽  
Vol 117 (42) ◽  
pp. 26118-26122
Author(s):  
Jaroslav Kysela ◽  
Manuel Erhard ◽  
Armin Hochrainer ◽  
Mario Krenn ◽  
Anton Zeilinger
Keyword(s):  
Angular Momentum ◽  
Degrees Of Freedom ◽  
General Scheme ◽  
Higher Dimensions ◽  
High Dimensional ◽  
Entangled States ◽  
Entangled State ◽  
Experimental Demonstration ◽  
Entanglement Generation ◽  
High Degree

We present an experimental demonstration of a general entanglement-generation framework, where the form of the entangled state is independent of the physical process used to produce the particles. It is the indistinguishability of multiple generation processes and the geometry of the setup that give rise to the entanglement. Such a framework, termed entanglement by path identity, exhibits a high degree of customizability. We employ one class of such geometries to build a modular source of photon pairs that are high-dimensionally entangled in their orbital angular momentum. We demonstrate the creation of three-dimensionally entangled states and show how to incrementally increase the dimensionality of entanglement. The generated states retain their quality even in higher dimensions. In addition, the design of our source allows for its generalization to various degrees of freedom and even for the implementation in integrated compact devices. The concept of entanglement by path identity itself is a general scheme and allows for construction of sources producing also customized states of multiple photons. We therefore expect that future quantum technologies and fundamental tests of nature in higher dimensions will benefit from this approach.

scholarly journals Topologically Protected Quantum Entanglement Emitters

2021 ◽  
Author(s):  
Jianwei Wang ◽  
Tianxiang Dai ◽  
Yutian Ao ◽  
Jueming Bao ◽  
Jun Mao ◽  
...  
Keyword(s):  
Quantum Entanglement ◽  
Entangled States ◽  
Entangled State ◽  
Ambient Conditions ◽  
Monolithically Integrated ◽  
Environmental Perturbations ◽  
Quantum Particles ◽  
Silicon Photonic ◽  
Einstein Podolsky Rosen ◽  
Photonic Quantum Computation

Abstract Entanglement and topology both portray nature at the fundamental level but in different manners. Entangled states of quantum particles are intrinsically sensitive to environment, whereas topological phases of matters represent natural robustness against environmental perturbations. Harnessing topology physics to protect entanglement thus has a great potential for reliable quantum applications. However, generating topologically-protected entanglement remains a significant challenge, which requires operating complex quantum devices in combined extreme conditions. Here we report topologically-protected quantum entanglement emitters, that emit topological Einstein-Podolsky-Rosen entangled state and topological multiphoton entangled state from a monolithically-integrated plug-and-play silicon-photonic chip in ambient conditions. The device emulating a photonic anomalous Floquet insulator allows the generation of up to four-photon topological entangled states at nontrivial edge modes. More importantly, we show that the Einstein-Podolsky-Rosen entanglement emitters can be topologically protected against artificial structure defects, by comparing tomographically measured fidelities of 0.968 ± 0.004 and 0.951 ± 0.01 for the perfect and defected emitters, respectively. Our topologically-protected entanglement emitters may find applications in photonic quantum computation and quantum simulation, and in the study of quantum topological physics.

scholarly journals A nondestructive Bell-state measurement on two distant atomic qubits

2021 ◽  
Author(s):  
Stephan Welte ◽  
Philip Thomas ◽  
Lukas Hartung ◽  
Severin Daiss ◽  
Stefan Langenfeld ◽  
...  
Keyword(s):  
Measurement Techniques ◽  
Bell State ◽  
Repeated Measurements ◽  
Entangled States ◽  
Entangled State ◽  
Initial State ◽  
Quantum Networks ◽  
Maximally Entangled State ◽  
Network Nodes ◽  
State Measurement

AbstractOne of the most fascinating aspects of quantum networks is their capability to distribute entanglement as a nonlocal communication resource1. In a first step, this requires network-ready devices that can generate and store entangled states2. Another crucial step, however, is to develop measurement techniques that allow for entanglement detection. Demonstrations for different platforms3–13 suffer from being not complete, destructive or local. Here, we demonstrate a complete and nondestructive measurement scheme14–16 that always projects any initial state of two spatially separated network nodes onto a maximally entangled state. Each node consists of an atom trapped inside an optical resonator from which two photons are successively reflected. Polarization measurements on the photons discriminate between the four maximally entangled states. Remarkably, such states are not destroyed by our measurement. In the future, our technique might serve to probe the decay of entanglement and to stabilize it against dephasing via repeated measurements17,18.

The Construction and Simulation Analysis of Three-Qubit Hxx Chain Refrigerator Based on Quantum Entangled States

2013 ◽  
Vol 380-384 ◽  
pp. 4849-4855
Author(s):  
Xing Kui Huang
Keyword(s):  
Field Strength ◽  
Simulation Analysis ◽  
Heat Engine ◽  
State Theory ◽  
Entangled States ◽  
Entangled State ◽  
Working Process ◽  
Mapping Analysis ◽  
Quantum Entangled States ◽  
Working Efficiency

Quantum entangled state theory is combined with quantum thermodynamics theory to build quantum entangled state heat engine. The basic nature of three-qubit Hxx chain, and all parameters of the orbit are analyzed. Energy model of quantum entangled state refrigerator in working process is taken as as a theoretical basis to construct three qubits Hxx chain refrigerator based on quantum entangled states. The working nature of the new quantum entangled state refrigerator under different field strength is studied. Compaired with two-qubit Hxxx chain refrigerator based on quantum entangled states and mapping analysis, the working efficiency of three qubits Hxx chain refrigerator based on quantum entangled states is much higher when the field strength is not zero and its working state is more stable.

Infinitely entangled states

2003 ◽  
Vol 3 (4) ◽  
pp. 281-306
Author(s):  
M. Keyl ◽  
D. Schlingemann ◽  
R.F. Werner
Keyword(s):  
Hilbert Spaces ◽  
Degrees Of Freedom ◽  
Entangled States ◽  
Entangled State ◽  
Bounded Operators ◽  
Infinite Dimensional ◽  
Infinite Dimensional Hilbert Space ◽  
Density Operators ◽  
Fundamental Paper ◽  
Extended Notion

For states in infinite dimensional Hilbert spaces entanglement quantities like the entanglement of distillation can become infinite. This leads naturally to the question, whether one system in such an infinitely entangled state can serve as a resource for tasks like the teleportation of arbitrarily many qubits. We show that appropriate states cannot be obtained by density operators in an infinite dimensional Hilbert space. However, using techniques for the description of infinitely many degrees of freedom from field theory and statistical mechanics, such states can nevertheless be constructed rigorously. We explore two related possibilities, namely an extended notion of algebras of observables, and the use of singular states on the algebra of bounded operators. As applications we construct the essentially unique infinite analogue of maximally entangled states, and the singular state used heuristically in the fundamental paper of Einstein, Rosen and Podolsky.

scholarly journals Probabilistic Resumable Quantum Teleportation of a Two-Qubit Entangled State

Entropy ◽  
2019 ◽  
Vol 21 (4) ◽  
pp. 352 ◽  
Author(s):  
Zhan-Yun Wang ◽  
Yi-Tao Gou ◽  
Jin-Xing Hou ◽  
Li-Ke Cao ◽  
Xiao-Hui Wang
Keyword(s):  
Quantum Channel ◽  
Quantum Teleportation ◽  
The State ◽  
Entangled States ◽  
Entangled State ◽  
Quantum Channels ◽  
Unknown State ◽  
Optimal Probability

We explicitly present a generalized quantum teleportation of a two-qubit entangled state protocol, which uses two pairs of partially entangled particles as quantum channel. We verify that the optimal probability of successful teleportation is determined by the smallest superposition coefficient of these partially entangled particles. However, the two-qubit entangled state to be teleported will be destroyed if teleportation fails. To solve this problem, we show a more sophisticated probabilistic resumable quantum teleportation scheme of a two-qubit entangled state, where the state to be teleported can be recovered by the sender when teleportation fails. Thus the information of the unknown state is retained during the process. Accordingly, we can repeat the teleportion process as many times as one has available quantum channels. Therefore, the quantum channels with weak entanglement can also be used to teleport unknown two-qubit entangled states successfully with a high number of repetitions, and for channels with strong entanglement only a small number of repetitions are required to guarantee successful teleportation.

MULTIPARTY REMOTELY PREPARING MULTIPARTITE EQUATORIAL ENTANGLED STATES IN HIGH DIMENSIONS

2011 ◽  
Vol 09 (06) ◽  
pp. 1437-1448
Author(s):  
YI-BAO LI ◽  
KUI HOU ◽  
SHOU-HUA SHI
Keyword(s):  
Quantum State ◽  
Quantum Channel ◽  
Success Probability ◽  
Quantum States ◽  
Remote State Preparation ◽  
Entangled States ◽  
Entangled State ◽  
High Dimensions ◽  
Original State ◽  
State Preparation

We propose two kinds of schemes for multiparty remote state preparation (MRSP) of the multiparticle d-dimensional equatorial quantum states by using partial entangled state as the quantum channel. Unlike more remote state preparation scheme which only one sender knows the original state to be remotely prepared, the quantum state is shared by two-party or multiparty in this scheme. We show that if and only if all the senders agree to collaborate with each other, the receiver can recover the original state with certain probability. It is found that the total success probability of MRSP is only by means of the smaller coefficients of the quantum channel and the dimension d.

Bidirectional quantum teleportation and cyclic quantum teleportation of multi-qubit entangled states via G-state

2020 ◽  
Vol 34 (28) ◽  
pp. 2050261
Author(s):  
Vikram Verma
Keyword(s):  
Quantum Channel ◽  
Quantum Teleportation ◽  
The Other ◽  
Entangled States ◽  
Entangled State ◽  
Bidirectional Quantum Teleportation

We propose a novel scheme for faithful bidirectional quantum teleportation (BQT) in which Alice can transmit an unknown N-qubit entangled state to Bob and at the same time Bob can transmit an unknown M-qubit entangled state to Alice by using a four-qubit entangled G-state as a quantum channel. We also propose a new scheme for cyclic QT of multi-qubit entangled states by using two G-states as a quantum channel. The advantage of our schemes is that it seems to be much simpler and requires reduced number of qubits in quantum channel as compared with the other proposed schemes.

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