FOUR-MODE EPR CONTINUOUS-VARIABLE ENTANGLED STATE AND ITS GENERATION

2002 ◽  
Vol 16 (22) ◽  
pp. 861-869 ◽  
Author(s):  
HONGYI FAN ◽  
XIANTING LIANG ◽  
JUNHUA CHEN
Keyword(s):  
Quantum Entanglement ◽  
Fock Space ◽  
Continuous Variable ◽  
Entangled States ◽  
Entangled State ◽  
Continuous Variables ◽  
Property A ◽  
Set Up

Based on Einstein, Podolsky and Rosen (EPR) quantum entanglement, we construct a new kind of four-mode entangled states of continuous variables in Fock space and examine its complete property and partly non-orthonormal property. A set-up of one beamsplitter and two polarizers can generate such a four-mode entangled state. The discussion can also be extended to constructing more particles' entangled states.

scholarly journals On-chip continuous-variable quantum entanglement

Nanophotonics ◽  
2016 ◽  
Vol 5 (3) ◽  
pp. 469-482 ◽  
Author(s):  
Genta Masada ◽  
Akira Furusawa
Keyword(s):  
Quantum Information ◽  
Integrated Circuits ◽  
Quantum Entanglement ◽  
Information Science ◽  
Essential Feature ◽  
Continuous Variable ◽  
Entangled State ◽  
Discrete Variable ◽  
Light Beams ◽  
Optical Circuits

AbstractEntanglement is an essential feature of quantum theory and the core of the majority of quantum information science and technologies. Quantum computing is one of the most important fruits of quantum entanglement and requires not only a bipartite entangled state but also more complicated multipartite entanglement. In previous experimental works to demonstrate various entanglement-based quantum information processing, light has been extensively used. Experiments utilizing such a complicated state need highly complex optical circuits to propagate optical beams and a high level of spatial interference between different light beams to generate quantum entanglement or to efficiently perform balanced homodyne measurement. Current experiments have been performed in conventional free-space optics with large numbers of optical components and a relatively large-sized optical setup. Therefore, they are limited in stability and scalability. Integrated photonics offer new tools and additional capabilities for manipulating light in quantum information technology. Owing to integrated waveguide circuits, it is possible to stabilize and miniaturize complex optical circuits and achieve high interference of light beams. The integrated circuits have been firstly developed for discrete-variable systems and then applied to continuous-variable systems. In this article, we review the currently developed scheme for generation and verification of continuous-variable quantum entanglement such as Einstein-Podolsky-Rosen beams using a photonic chip where waveguide circuits are integrated. This includes balanced homodyne measurement of a squeezed state of light. As a simple example, we also review an experiment for generating discrete-variable quantum entanglement using integrated waveguide circuits.

scholarly journals Continuous Variable Entanglement in Non-Zero Orbital Angular Momentum States

Proceedings ◽  
2019 ◽  
Vol 12 (1) ◽  
pp. 7
Author(s):  
Adriana Pecoraro ◽  
Filippo Cardano ◽  
Lorenzo Marrucci ◽  
Alberto Porzio
Keyword(s):  
Angular Momentum ◽  
Orbital Angular Momentum ◽  
Direct Detection ◽  
Hybrid Approach ◽  
Photon Number ◽  
Local Oscillator ◽  
Continuous Variable ◽  
Degree Of Freedom ◽  
Entangled State ◽  
Continuous Variables

Orbital angular momentum is a discrete degree of freedom that can access an infinite dimensional Hilbert space, thus enhancing the information capacity of a single optical beam. Continuous variables field quadratures allow achieving some quantum tasks in a more advantageous way with respect to the use of photon-number states. Here, we use a hybrid approach realizing bipartite continuous-variable Gaussian entangled state made up of two electromagnetic modes carrying orbital angular momentum. A q-plate is used for endowing a pair of entangled beams with such a degree of freedom. This quantum state is then completely characterized thanks to a novel design of a homodyne detector in which also the local oscillator is an orbital angular momentum-carrying beams so allowing the direct detection of vortex modes quadratures.

scholarly journals TIGHTENING THE EAVESDROPPING ACCESSIBLE INFORMATION FOR CONTINUOUS VARIABLE QUANTUM KEY DISTRIBUTION PROTOCOLS THAT INVOLVE NONMAXIMALLY ENTANGLEMENT

2012 ◽  
Vol 26 (16) ◽  
pp. 1250109 ◽  
Author(s):  
A. BECIR ◽  
M. R. B. WAHIDDIN
Keyword(s):  
Quantum Key Distribution ◽  
Key Distribution ◽  
Continuous Variable ◽  
Upper Bounds ◽  
Entangled States ◽  
Entangled State ◽  
Protocol Implementation ◽  
Accessible Information ◽  
Heisenberg Uncertainty

In this paper, we derive tight bounds for the eavesdropping attacks on continuous variable quantum key distribution (CV-QKD) protocol that involves nonmaximally entangled states. We show that deriving bounds on the eavesdropper's accessible information based on the Heisenberg uncertainty yields upper bounds, but those bounds are not tight. For this reason, we follow different techniques to derive the desired tight bounds. The new bounds are tight for all CV-QKD protocols that involve two-mode entangled state. Our derivations are applied to direct and reverse reconciliation schemes of protocol implementation, respectively.

Unbounded entanglement in nonlocal games

2015 ◽  
Vol 15 (15&16) ◽  
pp. 1317-1332
Author(s):  
Laura Mančinska ◽  
Thomas Vidick
Keyword(s):  
Quantum Entanglement ◽  
Finite Length ◽  
Success Probability ◽  
The Other ◽  
Entangled States ◽  
Entangled State ◽  
Local Dimension ◽  
Hardy's Paradox ◽  
First Time ◽  
Quantum Strategies

Quantum entanglement is known to provide a strong advantage in many two-party distributed tasks. We investigate the question of how much entanglement is needed to reach optimal performance. For the first time we show that there exists a purely classical scenario for which no finite amount of entanglement suffices. To this end we introduce a simple two-party nonlocal game H, inspired by Lucien Hardy’s paradox. In our game each player has only two possible questions and can provide bit strings of any finite length as answer. We exhibit a sequence of strategies which use entangled states in increasing dimension d and succeed with probability 1 − O(d−c ) for some c ≥ 0.13. On the other hand, we show that any strategy using an entangled state of local dimension d has success probability at most 1 − Ω(d−2 ). In addition, we show that any strategy restricted to producing answers in a set of cardinality at most d has success probability at most 1 − Ω(d−2 ). Finally, we generalize our construction to derive similar results starting from any game G with two questions per player and finite answers sets in which quantum strategies have an advantage.

Implementation of continuous variable quantum cryptography in optical fibres using a go-&-return configuration

2006 ◽  
Vol 6 (4&5) ◽  
pp. 326-335
Author(s):  
M. Legré ◽  
H. Zbinden ◽  
N. Gisin
Keyword(s):  
Quantum Cryptography ◽  
Quantum Key Distribution ◽  
Key Distribution ◽  
Continuous Variable ◽  
Optical Fibres ◽  
Continuous Variables ◽  
Phase Fluctuations ◽  
Degree Of Stability ◽  
Set Up ◽  
High Degree

We demonstrate an implementation of quantum key distribution with continuous variables based on a go-&-return configuration over distances up to 14km. This configuration leads to self-compensation of polarisation and phase fluctuations. We observe a high degree of stability of our set-up over many hours.

THE APPLICATION AND CHARACTERISTICS OF THE COHERENT ENTANGLED STATE |β, x〉

2011 ◽  
Vol 25 (12) ◽  
pp. 1611-1618
Author(s):  
YUN-HAI ZHANG ◽  
XING-LEI XU ◽  
SHI-MIN XU ◽  
HONG-QI LI
Keyword(s):  
Fock Space ◽  
Entangled States ◽  
Entangled State ◽  
Quantum Mechanical ◽  
Completeness Relation ◽  
Schmidt Decomposition ◽  
Experimental Scheme ◽  
Quantum Mechanical Representation

The coherent entangled state |β, x〉 is proposed in Fock space, which exhibits both the properties of the coherent and entangled states. The |β, x〉 makes up a new quantum mechanical representation, and the completeness relation of |β, x〉 is proved by virtue of the technique of integral within an ordered product of operators. The corresponding Schmidt decomposition of |β, x〉 is investigated. Furthermore, a feasible experimental scheme of |β, x〉 is presented, and generalized P-representation is constructed in the coherent entangled state |β, x〉.

scholarly journals Phase-Conjugate-State Pairs in Entangled States

2012 ◽  
Vol 2012 ◽  
pp. 1-12
Author(s):  
Ryo Namiki
Keyword(s):  
Continuous Variable ◽  
Entangled States ◽  
Entangled State ◽  
Discrete Variable ◽  
Maximally Entangled State ◽  
Phase Conjugate ◽  
Singlet States ◽  
Conjugate State ◽  
Local Access

We consider the probability that a bipartite quantum state contains phase-conjugate-state (PCS) pairs and/or identical-state pairs as signatures of quantum entanglement. While the fraction of the PCS pairs directly indicates the property of a maximally entangled state, the fraction of the identical-state pairs negatively determines antisymmetric entangled states such as singlet states. We also consider the physical limits of these probabilities. This imposes fundamental restrictions on the pair appearance of the states with respect to the local access of the physical system. For continuous-variable system, we investigate similar relations by employing the pairs of phase-conjugate coherent states. We also address the role of the PCS pairs for quantum teleportation in both discrete-variable and continuous-variable systems.

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.

TRIPARTITE ENTANGLED STATE REPRESENTATION AND ITS APPLICATION IN QUANTUM TELEPORTATION

2002 ◽  
Vol 16 (30) ◽  
pp. 1193-1200 ◽  
Author(s):  
HONGYI FAN ◽  
NIANQUAN JIANG ◽  
HAILIANG LU
Keyword(s):  
Fock Space ◽  
Entangled State ◽  
Entangled State Representation ◽  
Squeezed State ◽  
State Representation ◽  
Schmidt Decomposition ◽  
Tripartite Entangled State ◽  
Relative Coordinates ◽  
The Common ◽  
Set Up

We set up a tripartite entangled state representation |p, χ2, χ3> in three-mode Fock space which is composed of the common eigenvectors of three particles' relative coordinates X1 - X2 and X1 - X3 as well as the total momentum P1 + P2 + P3. The Schmidt decomposition of |p, χ2, χ3 > is made and its application in quantum teleporting a two-particle entangled state or a two-mode squeezed state is analyzed.

Sign in / Sign up

Export Citation Format

Share Document