scholarly journals Coherent preorder of quantum states

2020 ◽  
Vol 20 (13&14) ◽  
pp. 1124-1137
Author(s):  
Zhaofang Bai ◽  
Shuanping Shuanping Du
Keyword(s):  
Information Processing ◽  
Quantum Information ◽  
Coherent States ◽  
Quantum Coherence ◽  
Quantum Information Processing ◽  
Quantum States ◽  
Mixed States ◽  
Quantum Hypothesis ◽  
Quantum Hypothesis Testing

As an important quantum resource, quantum coherence play key role in quantum information processing. It is often concerned with manipulation of families of quantum states rather than individual states in isolation. Given two pairs of coherent states $(\rho_1,\rho_2)$ and $(\sigma_1,\sigma_2)$, we are aimed to study how can we determine if there exists a strictly incoherent operation $\Phi$ such that $\Phi(\rho_i) =\sigma_i,i = 1,2$. This is also a classic question in quantum hypothesis testing. In this note, structural characterization of coherent preorder under strongly incoherent operations is provided. Basing on the characterization, we propose an approach to realize coherence distillation from rank-two mixed coherent states to $q$-level maximally coherent states. In addition, one scheme of coherence manipulation between rank-two mixed states is also presented.

scholarly journals Construction of genuinely entangled subspacesand the associated bounds on entanglement measures for mixed states

2021 ◽  
Author(s):  
Konstantin Antipin
Keyword(s):  
Information Processing ◽  
Quantum Information ◽  
Lower Bounds ◽  
Quantum Information Processing ◽  
Multipartite Entanglement ◽  
Quantum Channels ◽  
Valuable Resource ◽  
Mixed States ◽  
Entanglement Measures ◽  
Pure States

Abstract Genuine entanglement is the strongest form of multipartite entanglement. Genuinely entangled pure states contain entanglement in every bipartition and as such can be regarded as a valuable resource in the protocols of quantum information processing. A recent direction of research is the construction of genuinely entangled subspaces — the class of subspaces consisting entirely of genuinely entangled pure states. In this paper we present methods of construction of such subspaces including those of maximal possible dimension. The approach is based on the composition of bipartite entangled subspaces and quantum channels of certain types. The examples include maximal subspaces for systems of three qubits, four qubits, three qutrits. We also provide lower bounds on two entanglement measures for mixed states, the concurrence and the convex-roof extended negativity, which are directly connected with the projection on genuinely entangled subspaces.

Proposal for dimensionality testing in QPQ

2018 ◽  
Vol 18 (13&14) ◽  
pp. 1125-1142
Author(s):  
Arpita Maitra ◽  
Bibhas Adhikari ◽  
Satyabrata Adhikari
Keyword(s):  
Information Processing ◽  
Quantum Information ◽  
Quantum System ◽  
Quantum State ◽  
Quantum Information Processing ◽  
Quantum States ◽  
Quantum Private Query ◽  
Unfair Advantage ◽  
Security Proofs

Recently, dimensionality testing of a quantum state has received extensive attention (Ac{\'i}n et al. Phys. Rev. Letts. 2006, Scarani et al. Phys. Rev. Letts. 2006). Security proofs of existing quantum information processing protocols rely on the assumption about the dimension of quantum states in which logical bits are encoded. However, removing such assumption may cause security loophole. In the present paper, we show that this is indeed the case. We choose two players' quantum private query protocol by Yang et al. (Quant. Inf. Process. 2014) as an example and show how one player can gain an unfair advantage by changing the dimension of subsystem of a shared quantum system. To resist such attack we propose dimensionality testing in a different way. Our proposal is based on CHSH like game. As we exploit CHSH like game, it can be used to test if the states are product states for which the protocol becomes completely vulnerable.

scholarly journals Amination of the Gd@C82 endohedral fullerene: tunable substitution effect on quantum coherence behaviors

2020 ◽  
Vol 11 (39) ◽  
pp. 10737-10743 ◽  
Author(s):  
Zheng Liu ◽  
Huan Huang ◽  
Ye-Xin Wang ◽  
Bo-Wei Dong ◽  
Bao-Yun Sun ◽  
...  
Keyword(s):  
Information Processing ◽  
Quantum Information ◽  
Quantum Coherence ◽  
Quantum Information Processing ◽  
Substitution Effect ◽  
Quantum Phase ◽  
Endohedral Fullerene ◽  
Memory Time ◽  
Phase Memory

Amination of the endohedral fullerene Gd@C82 exhibits enhanced quantum phase memory time and tunable substitution effect for quantum information processing.

scholarly journals Heralded orthogonalisation of coherent states and their conversion to discrete-variable superpositions

2017 ◽  
Vol 4 (1) ◽  
pp. 35-43 ◽  
Author(s):  
Regina Kruse ◽  
Christine Silberhorn ◽  
Tim Bartley
Keyword(s):  
Information Processing ◽  
Quantum Information ◽  
Coherent States ◽  
Quantum Information Processing ◽  
Fundamental Property ◽  
Discrete Variable ◽  
Successful Operation ◽  
State Discrimination ◽  
Unambiguous State Discrimination

Abstract The nonorthogonality of coherent states is a fundamental property which prevents them from being perfectly and deterministically discriminated. Here, we present an experimentally feasible protocol for the probabilistic orthogonalisation of a pair of coherent states, independent of their amplitude and phase. In contrast to unambiguous state discrimination, a successful operation of our protocol is heralded without measuring the states. As such, they remain suitable for further manipulation and the obtained orthogonal states serve as a discretevariable basis. Therefore, our protocol doubles as a simple continuous-to-discrete variable converter, which may find application in hybrid continuous-discrete quantum information processing protocols.

Ququats as superposition of coherent states and their application in quantum information processing

2021 ◽  
pp. 2150013
Author(s):  
Manoj K. Mishra ◽  
Hari Prakash ◽  
Vibhuti B. Jha
Keyword(s):  
Hilbert Space ◽  
Information Processing ◽  
Quantum Information ◽  
Quantum Channel ◽  
Coherent States ◽  
Beam Splitter ◽  
Quantum Information Processing ◽  
Key Distribution ◽  
Dimensional Hilbert Space ◽  
Entangled Coherent States

Superposition of optical coherent states (SCS) [Formula: see text], possessing opposite phases, plays an important role as qubits in quantum information processing tasks like quantum computation, teleportation, key distribution, etc. and are of fundamental importance in testing quantum mechanics. Passage of such SCS from a 50:50 beam splitter leads to generation of entangled coherent states. Recently, ququats and qutrits defined in four- and three-dimensional Hilbert space, respectively, have attracted much attention as they offer advantage in secure quantum communication. However, practical utilization of these advantages essentially requires physical realization of quantum optical ququats and qutrits. Here, we define four new multi-photonic states (MPS) with [Formula: see text] (here, [Formula: see text] or 3 and [Formula: see text]) numbers of photon and show how the SCS can be used to encode ququat using these MPS as basis vectors of a four-dimensional Hilbert space. When these MPS fall upon a 50:50 beam splitter, the resulting states are bipartite four-component entangled coherent states (BFECS) equivalently representing the entangled ququats. We briefly discuss the photon statistical properties of such MPS and BFECS. We show that these MPS and BFECS can be synthesized using even coherent states as input to an interferometer. We give a simple linear optical protocol for almost perfect teleportation of a ququat encoded in SCS with the aid of BFECS as quantum channel. We also describe how these ququats can be used for realization of higher-dimensional BB84 protocol to increase the security of quantum key distribution. Finally, we discuss the possible advantages of using SCS as ququats and BFECS as quantum channel in different quantum information processing tasks.

Super fidelity and related metrics

Open Physics ◽  
2011 ◽  
Vol 9 (4) ◽  
Author(s):  
Zhi-Hua Chen ◽  
Zhihao Ma ◽  
Fu-Lin Zhang ◽  
Jing-Ling Chen
Keyword(s):  
Information Processing ◽  
Quantum Information ◽  
Quantum Information Processing ◽  
Quantum States

AbstractWe report a new metric of quantum states. This metric is built up from super-fidelity, which has a deep connection with the Uhlmann-Jozsa fidelity and plays an important role in quantum information processing. We find that the new metric possesses some interesting properties.

scholarly journals Almost minimum error discrimination of N-ary weak coherent states by Jaynes-Cummings Hamiltonian dynamics

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Min Namkung ◽  
Younghun Kwon
Keyword(s):  
Information Processing ◽  
Quantum Information ◽  
Quantum State ◽  
Coherent States ◽  
Quantum Information Processing ◽  
Hamiltonian Dynamics ◽  
Quantum State Discrimination ◽  
Minimum Error ◽  
State Discrimination

AbstractQuantum state discrimination of coherent states has been one of important problems in quantum information processing. Recently, R. Han et al. showed that minimum error discrimination of two coherent states can be nearly done by using Jaynes-Cummings Hamiltonian. In this paper, based on the result of R. Han et al., we propose the methods where minimum error discrimination of more than two weak coherent states can be nearly performed. Specially, we construct models which can do almost minimum error discrimination of three and four coherent states. Our result can be applied to quantum information processing of various coherent states.

Entangled coherent states for quantum information processing

Optik ◽  
2014 ◽  
Vol 125 (15) ◽  
pp. 3788-3790 ◽  
Author(s):  
Syed Hamad Bukhari ◽  
Samia Aslam ◽  
Faiza Mustafa ◽  
Ayesha Jamil ◽  
Salman Naeem Khan ◽  
...  
Keyword(s):  
Information Processing ◽  
Quantum Information ◽  
Coherent States ◽  
Quantum Information Processing ◽  
Entangled Coherent States
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