A method for efficiently estimating non-Gaussianity of continuous-variable quantum states

2020 ◽  
Vol 74 (1) ◽  
Author(s):  
Shao-Hua Xiang ◽  
Yu-Jing Zhao ◽  
Cheng Xiang ◽  
Wei Wen ◽  
Xue-Wen Long
Keyword(s):  
Continuous Variable ◽  
Quantum States

Quantum dialogue protocol with four-mode continuous variable GHZ state

2019 ◽  
Vol 33 (05) ◽  
pp. 1950033 ◽  
Author(s):  
Ming-Hui Zhang ◽  
Jin-Ye Peng ◽  
Zheng-Wen Cao
Keyword(s):  
Channel Capacity ◽  
Quantum Channel ◽  
Beam Splitter ◽  
Information Leakage ◽  
Continuous Variable ◽  
Ghz State ◽  
Quantum States ◽  
Quantum Dialogue ◽  
Discrete Variable ◽  
Secret Information

Quantum dialogue can realize the mutual transmission of secret information between two legal users. In most of the existing quantum dialogue protocols, the information carriers applied in quantum dialogue are discrete variable (DV) quantum states. However, there are certain limitations on the preparation and detection of DV quantum states with current techniques. Continuous variable (CV) quantum states can overcome these problems effectively while improving the quantum channel capacity. In this paper, we propose a quantum dialogue protocol with four-mode continuous variable GHZ state. Compared with the existing CV-based quantum dialogue protocols, the protocol allows two users to transmit two groups of secret information with different lengths to each other simultaneously. The channel capacity of the protocol has been improved as each traveling mode carries two- or four-bits of information. In addition, the protocol has been proved to be secure against information leakage problem and some common attacks, such as beam splitter attack and intercept-and-resend attack.

TELEPORTATION OF ANY FORM OF SINGLE-MODE QUANTUM STATES

2006 ◽  
Vol 20 (02n03) ◽  
pp. 97-103
Author(s):  
TONG-QIANG SONG
Keyword(s):  
Quantum Channel ◽  
Quantum Teleportation ◽  
Single Mode ◽  
Continuous Variable ◽  
Quantum States ◽  
Squeezed Vacuum ◽  
Einstein Podolsky Rosen ◽  
Epr Pair

By using the two-mode Einstein–Podolsky–Rosen (EPR) pair eigenstates or the two-mode squeezed vacuum as quantum channel we study the quantum teleportation of any form of single-mode quantum states (which include discrete and continuous variable quantum states). The elegant properties of the EPR pair eigenstates bring much convenience to our discussion.

scholarly journals About the use of fidelity in continuous variable systems

2014 ◽  
Vol 12 (02) ◽  
pp. 1461015 ◽  
Author(s):  
Antonio Mandarino ◽  
Matteo Bina ◽  
Stefano Olivares ◽  
Matteo G. A. Paris
Keyword(s):  
Physical Properties ◽  
Continuous Variable ◽  
Quantum States ◽  
High Fidelity ◽  
Non Gaussian ◽  
Additional Constraints

We present examples of continuous variable (CV) states having high fidelity to a given target, say F > 0.9 or F > 0.99, and still showing striking differences in their physical properties, including classical and quantum states within the set, separable and entangled ones, or nearly Gaussian and strongly non-Gaussian ones. We also show that the phenomenon persists also when one imposes additional constraints on the energy or the squeezing fraction of the states, thus generally questioning the use of fidelity to assess properties of CV systems without a tomographic set of additional constraints.

scholarly journals Quantum channel of continuous variable teleportation and nonclassicality of quantum states

2002 ◽  
Vol 4 (2) ◽  
pp. 114-122 ◽  
Author(s):  
Masahiro Takeoka ◽  
Masashi Ban ◽  
Masahide Sasaki
Keyword(s):  
Quantum Channel ◽  
Continuous Variable ◽  
Quantum States

scholarly journals Quantum communication with coherent states of light

2017 ◽  
Vol 375 (2099) ◽  
pp. 20160235 ◽  
Author(s):  
Imran Khan ◽  
Dominique Elser ◽  
Thomas Dirmeier ◽  
Christoph Marquardt ◽  
Gerd Leuchs
Keyword(s):  
Coherent States ◽  
Secure Communication ◽  
Communication Systems ◽  
Quantum Communication ◽  
Continuous Variable ◽  
Quantum States ◽  
Complexity Of Algorithms ◽  
Laser Systems ◽  
Quantum Technology ◽  
Photon States

Quantum communication offers long-term security especially, but not only, relevant to government and industrial users. It is worth noting that, for the first time in the history of cryptographic encoding, we are currently in the situation that secure communication can be based on the fundamental laws of physics (information theoretical security) rather than on algorithmic security relying on the complexity of algorithms, which is periodically endangered as standard computer technology advances. On a fundamental level, the security of quantum key distribution (QKD) relies on the non-orthogonality of the quantum states used. So even coherent states are well suited for this task, the quantum states that largely describe the light generated by laser systems. Depending on whether one uses detectors resolving single or multiple photon states or detectors measuring the field quadratures, one speaks of, respectively, a discrete- or a continuous-variable description. Continuous-variable QKD with coherent states uses a technology that is very similar to the one employed in classical coherent communication systems, the backbone of today’s Internet connections. Here, we review recent developments in this field in two connected regimes: (i) improving QKD equipment by implementing front-end telecom devices and (ii) research into satellite QKD for bridging long distances by building upon existing optical satellite links. This article is part of the themed issue ‘Quantum technology for the 21st century’.

Cohering power and decohering power of Gaussian unitary operations

2019 ◽  
Vol 19 (7&8) ◽  
pp. 575-586
Author(s):  
Yangyang Wang ◽  
Xiaofei Qi ◽  
Jinchuan Hou ◽  
Rufen Ma
Keyword(s):  
Relative Entropy ◽  
Continuous Variable ◽  
Quantum States ◽  
Entropy Measure ◽  
Quantum Channels ◽  
Gaussian States ◽  
Basic Properties ◽  
Suitable Measure

Having a suitable measure to quantify the coherence of quantum states, a natural task is to evaluate the power of quantum channels for creating or destroying the coherence of input quantum states. In the present paper, by introducing the maximal coherent Gaussian states based on the relative entropy measure of coherence, we propose the (generalized) cohering power and the (generalized) decohering power of Gaussian unitary operations for continuous-variable systems. Some basic properties are obtained and the cohering power and decohering power of two special kinds of Gaussian unitary operations are calculated.

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