scholarly journals ENTANGLEMENT CRITERION FOR COHERENT SUBTRACTION AND COHERENT ADDITION OF BIPARTITE CONTINUOUS VARIABLE STATES

2013 ◽  
Vol 11 (06) ◽  
pp. 1350060
Author(s):  
LI-ZHEN JIANG ◽  
XIAO-YU CHEN ◽  
TIAN-YU YE ◽  
FANG-YU HONG ◽  
LIANG-NENG WU
Keyword(s):  
Thermal Noise ◽  
Photon Number ◽  
Sufficient Conditions ◽  
Continuous Variable ◽  
Entangled State ◽  
Gaussian States ◽  
Non Gaussian ◽  
Entanglement Criterion ◽  
Entanglement Conditions ◽  
Thermal States

We study the entanglement conditions of two quite general classes of two-mode non-Gaussian states. Using computable cross norm and realignment criterion, we obtain the sufficient conditions of entanglement for coherently added or subtracted two-mode squeezed thermal states, and the sufficient condition of entanglement for any photon number entangled state (PNES) evolving in a thermal noise and amplitude damping channel.

Teleportation improvement by noiseless linear amplification

2019 ◽  
Vol 19 (11&12) ◽  
pp. 935-951
Author(s):  
Hamza Adnane ◽  
Matteo G.A. Paris
Keyword(s):  
Coherent States ◽  
Large Range ◽  
Low Energy ◽  
Entangled State ◽  
Continuous Variables ◽  
Linear Amplification ◽  
Gaussian States ◽  
Linear Amplifier ◽  
Twin Beam ◽  
Non Gaussian

We address de-Gaussification of continuous variables Gaussian states by optimal non-deterministic noiseless linear amplifier (NLA) and analyze in details the properties of the amplified states. In particular, we investigate the entanglement content and the non-Gaussian character for the class of non-Gaussian entangled state obtained by using NL-amplification of two-mode squeezed vacua (twin-beam, TWB). We show that entanglement always increases, whereas improved EPR correlations are observed only when the input TWB has low energy. We then examine a Braunstein-Kimble-like protocol for the teleportation of coherent states, and compare the performances of TWB-based teleprotation with those obtained using NL-amplified resources. We show that teleportation fidelity and security may be improved for a large range of NLA parameters (gain and threshold).

scholarly journals Fidelity-based unitary operation-induced quantum correlation for continuous-variable systems

2019 ◽  
Vol 17 (04) ◽  
pp. 1950035
Author(s):  
Liang Liu ◽  
Xiaofei Qi ◽  
Jinchuan Hou
Keyword(s):  
Quantum Correlation ◽  
Quantum Correlations ◽  
Continuous Variable ◽  
Gaussian Channel ◽  
Simple Computation ◽  
Gaussian States ◽  
Text Mode ◽  
Computation Formula ◽  
Geometric Measurement ◽  
Thermal States

We propose a measure of nonclassical correlation [Formula: see text] in terms of local Gaussian unitary operations based on square of the fidelity [Formula: see text] for bipartite continuous-variable systems. This quantity is easier to be calculated or estimated and is a remedy for the local ancilla problem associated with the geometric measurement-induced nonlocality. A simple computation formula of [Formula: see text] for any [Formula: see text]-mode Gaussian states is presented and an estimation of [Formula: see text] for any [Formula: see text]-mode Gaussian states is given. For any [Formula: see text]-mode Gaussian states, [Formula: see text] does not increase after performing a local Gaussian channel on the unmeasured subsystem. Comparing [Formula: see text] in scale with other quantum correlations such as Gaussian geometric discord for two-mode symmetric squeezed thermal states reveals that [Formula: see text] is much better in detecting quantum correlations of Gaussian states.

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 GAUSSIAN GEOMETRIC DISCORD

2011 ◽  
Vol 09 (07n08) ◽  
pp. 1773-1786 ◽  
Author(s):  
GERARDO ADESSO ◽  
DAVIDE GIROLAMI
Keyword(s):  
Quantum Discord ◽  
Gaussian Quadrature ◽  
Continuous Variable ◽  
Upper And Lower Bounds ◽  
Gaussian States ◽  
Physical Constraints ◽  
Geometric Measure ◽  
Classical Correlations ◽  
Qubit States ◽  
Thermal States

We extend the geometric measure of quantum discord, introduced and computed for two-qubit states, to quantify non-classical correlations in composite Gaussian states of continuous variable systems. We lay the formalism for the evaluation of a Gaussian geometric discord in two-mode Gaussian states, and present explicit formulas for the class of two-mode squeezed thermal states. In such a case, under physical constraints of bounded mean energy, geometric discord is shown to admit upper and lower bounds for a fixed value of the conventional (entropic) quantum discord. We finally discuss alternative geometric approaches to quantify Gaussian quadrature correlations.

Nonclassical properties and decoherence of fields in photon-added squeezing-enhanced thermal states

2014 ◽  
Vol 28 (19) ◽  
pp. 1450115 ◽  
Author(s):  
Zhen Wang ◽  
Xiang-guo Meng ◽  
Heng-mei Li ◽  
Hong-chun Yuan
Keyword(s):  
Thermal Noise ◽  
Photon Number ◽  
Sufficient Time ◽  
Thermal Photon ◽  
Time Interaction ◽  
Decoherence Time ◽  
Nonclassical Properties ◽  
Poissonian Statistics ◽  
Decoherence Effect ◽  
Thermal States

We put forward the photon-added squeezing-enhanced thermal states (PASETS) theoretically by adding photon to the squeezed enhancing thermal states (SETS) repeatedly. Based on the normally ordered density operator of PASETS, we investigate the nonclassical behavior of the PASETS by evaluating, both analytically and numerically, Mandel's Q-parameter, photon-number distribution (PND), and Wigner function (WF). It is found that smaller squeezing parameter r and thermal photon number nc can lead to more chance of the appearance of sub-Poissonian statistics. And it is shown that the PND of PASETS exhibit more remarkable oscillations than that of SETS in stronger squeezing case. The WF exhibit partial negativity in phase space and the squeezing parameter r can result in both squeezing and rotating effect. By investigating the fidelity between PASETS and SETS shows that the fidelity tender to steady values in the high value of squeezing parameter or thermal photon number. In addition, the decoherence effect on the PASETS is examined by the time-evolution of the analytical WF in thermal channel. The results show that the PASETS shall lose nonclassicality and non-Gaussianity and reduce to classical states with Gaussian distribution after sufficient time interaction with the thermal noise. And larger photon-added number or thermal photon number shall render shorter decoherence time.

scholarly journals Photon-number discrimination without a photon counter and its application to reconstructing non-Gaussian states

2011 ◽  
Vol 84 (5) ◽  
Author(s):  
H. M. Chrzanowski ◽  
J. Bernu ◽  
B. M. Sparkes ◽  
B. Hage ◽  
A. P. Lund ◽  
...  
Keyword(s):  
Photon Number ◽  
Photon Counter ◽  
Gaussian States ◽  
Number Discrimination ◽  
Non Gaussian
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