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## Schmidt-mode analysis of quadrature entanglement in superpositions of two-mode multiphoton states

Physica Scripta. 2020. Vol. 95. No. 6. Article 064001.

M V Fedorov

Schmidt-decomposition formalism is proposed to be used for evaluation of the degree of

quadrature entanglement in two-mode multiphoton states. A series of examples are considered,

including analysis of the quadrature entanglement of the two-mode squeezed vacuum. Singlemode

and two-mode coherent states with stochastic phases are analyzed by the same method

though in this case features of quadrature states are interpreted in terms of decoherence rather

than entanglement.

M V Fedorov, Laser Physics 2019 Vol. 29 No. 12 Article 124006

A brief overview of entanglement characterization is given in the cases of biphoton and
multiphoton polarization states. The importance of the approach is stressed based on the
Schmidt decomposition. This method is applied to the characterization of the quadrature
entanglement in two-mode multiphoton states. The fruitfulness of this approach is illustrated
by a series of examples. ...

Added: December 3, 2019

Федоров М. В., Physical Review A: Atomic, Molecular, and Optical physics 2016 Vol. 93 No. 3 Article 033830

Purely azimuthal entanglement is analyzed for noncollinear frequency-degenerate biphoton states. The degree
of azimuthal entanglement is found to be very high, with the Schmidt parameter K on the order of the ratio of the
pump waist to its wavelength. A scheme is suggested for partial realization of this high entanglement resource in
the form of a multichannel Schmidt-type ...

Added: February 24, 2018

Vintskevich S. V., Grigoriev D. A., Miklin N. I. et al., Laser Physics Letters 2020 Vol. 17 No. 3 Article 035209

Density matrices of pure multiphoton Fock polarization states and their resultant reduced density matrices of mixed states are expressed in similar ways in terms of matrices of correlators, defined as averaged products of equal numbers of creation and annihilation operators. The degree of entanglement of considered states is evaluated for various combinations of parameters of states and characters of ...

Added: April 6, 2021

В. П. Спиридонов, Теоретическая и математическая физика 2022 Т. 212 № 3 С. 403-413

We describe a family of quantum states of the Schrödinger cat type as superpositions of the harmonic oscillator coherent states with coefficients defined by the quadratic Gauss sums. These states emerge as eigenfunctions of the lowering operators obtained after canonical transformations of the Heisenberg–Weyl algebra associated with the ordinary and fractional Fourier transformations. The first member of this family is given by the well ...

Added: August 30, 2022

K S Kravtsov, Laser Physics Letters 2023 Vol. 20 No. 8 Article 085203

The paper analyzes security aspects of practical entanglement-based quantum key distribution
(QKD), namely, BBM92 or entanglement-based BB84 protocol. Similar to prepare-and-measure
QKD protocols, practical implementations of the entanglement-based QKD have to rely upon nonideal
photon sources. A typical solution for entanglement generation is the spontaneous parametric
down-conversion. However, this process creates not only single photon pairs, but also quantum
states ...

Added: March 12, 2024

Novikova E., Наноструктуры. Математическая физика и моделирование 2016 Т. 15 № 2 С. 75-98

Дано описание спектральных характеристик планарной ловушки Пеннинга с кольцевой конфигурацией электродов и магнитным полем, отклоненным от аксиальной оси. Найдены соотношения между физическими параметрами, при которых наступает комбинированный частотный резонанс в гармонической (квадратичной) части гамильтониана вблизи центра ловушки. Усредненная ангармоническая часть гамильтониана представлена обыкновенным дифференциальным оператором второго порядка с полиномиальными коэффициентами, найдена асимптотика его собственных значений ...

Added: October 23, 2016

Pashin D., Bastrakova M., Arkady Satanin et al., Sensors 2022 Vol. 22 No. 17 Article 6580

We study bifurcation behavior of a high-quality (high-Q) Josephson oscillator coupled to a superconducting qubit. It is shown that the probability of capture into the state of dynamic equilibrium is sensitive to qubit states. On this basis we present a new measurement method for the superposition state of a qubit due to its influence on ...

Added: October 26, 2022

Vinetskaya P. M., Kravtsov K. S., Borshchevskaia N. A. et al., Laser Physics Letters 2023 Vol. 20 No. 5 Article 055201

Entangled quantum key distribution (QKD) is a promising way to generate pairs of unconditionally secret keys. In this paper we review possible realizations of entanglement-based QKD and assess their feasibility in terms of implementation complexity and provided security. We also propose a novel active basis choice approach that enables to use only one single-photon detector ...

Added: March 12, 2024

Novikova E., Mathematical notes 2019 Vol. 106 No. 6 P. 940-956

The algebra of symmetries of the quantum three-frequency hyperbolic resonance oscillator is studied. It is shown that this algebra is determined by a nite set of generators with polynomial commutation relations. The irreducible representations of this algebra and the corresponding coherent states are constructed. ...

Added: October 28, 2019

Karasev M., Novikova E., Mathematical notes 2018 Vol. 104 No. 5-6 P. 833-847

For the three-frequency quantum resonance oscillator, the reducible case, where its frequencies are integer and at least one pair of frequencies has a nontrivial common divisor, is studied. It is shown how the description of the algebra of symmetries of such an oscillator can be reduced to the irreducible case of pairwise coprime integer frequencies. ...

Added: October 31, 2018

Seidelmann T., Cosacchi M., Cygorek M. et al., Advanced Quantum Technologies 2021 Vol. 4 No. 1 Article 2000108

Bell states are the most prominent maximally entangled photon states. In a typical four-level emitter, like a semiconductor quantum dot, the photon states exhibit only one type of Bell state entanglement. By adding an external driving to the emitter system, also other types of Bell state entanglement are reachable without changing the polarization basis. In ...

Added: February 24, 2022

Akulin, Physical Review A (USA) 2015 Vol. 92 No. 4

Using geometric means, we first consider a density matrix decomposition of a multipartite quantum system of a finite dimension into two density matrices: a separable one, also known as the best separable approximation, and an essentially entangled one, which contains no product state components. We show that this convex decomposition can be achieved in practice ...

Added: November 1, 2020

Burmistrov I., Tikhonov K., Gornyi I. V. et al., Annals of Physics 2017 Vol. 383 P. 140-156

We study the entanglement entropy and particle number cumulants for a system of disordered noninteracting fermions in d dimensions. We show, both analytically and numerically, that for a weak disorder the entanglement entropy and the second cumulant (particle number variance) are proportional to each other with a universal coefficient. The corresponding expressions are analogous to ...

Added: June 16, 2017

Seidelman T., Schimpf C., Bracht T. et al., Physical Review Letters 2022 Vol. 129 No. 19 Article 193604

Entangled photon pairs are key to many novel applications in quantum technologies. Semiconductor quantum dots can be used as sources of on-demand, highly entangled photons. The fidelity to a fixed maximally entangled state is limited by the excitonic fine-structure splitting. This work demonstrates that, even if this splitting is absent, the degree of entanglement cannot ...

Added: December 1, 2022

Katushkina O. A., Quemerais E., Izmodenov V.V. et al., JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS 2017 Vol. 122 No. 11 P. 10921-10937

In this work, we present for the first time the Lyman α intensities measured by Voyager 1/UVS in 2003–2014 (at 90–130 AU from the Sun). During this period Voyager 1 measured the Lyman α emission in the outer heliosphere at an almost fixed direction close to the upwind (i.e.“ toward the interstellar flow). The data show an unexpected behavior in 2003–2009: the ...

Added: January 26, 2018

Aaij R., Abdelmotteleb A. S., Abellan Beteta C. et al., The European Physical Journal C - Particles and Fields 2023 Vol. 83 Article 543

https://link.springer.com/article/10.1140/epjc/s10052-023-11673-x#Abs1 ...

Added: December 4, 2023

Ружицкая Д. Д., САМОЙЛЕНКО А. А., Иванов А. Д. et al., Optoelectronics, Instrumentation and Data Processing 2017 Vol. 54 No. 1 P. 1-8

This paper presents an algorithm for processing the transmission spectra of whisperinggallery optical microcavities for use as a nanoparticle detector. The algorithm is based on the broadening of the microcavity resonance curve during precipitation of nanoparticles on the microcavity surface. Experimental results on the detection of particles are compared with Langmuir adsorption theory. The contribution ...

Added: May 25, 2018

М. : National Instruments Russia, 2017

Содержание сборника составляют доклады с результатами оригинальных исследований и технических решений, ранее не публиковавшиеся. Мы надеемся, что предлагаемый сборник окажется полезным для специалистов, работающих в различных областях науки и техники, для широкого круга преподавателей, аспирантов и студентов ВУЗов, а также для преподавателей средних школ и технических колледжей. ...

Added: May 10, 2017

Загорский Д. Л., Долуденко И. М., Каневский В. М. et al., Известия РАН. Серия физическая 2021 Т. 85 № 8 С. 1088-1094

FeCo and FeNi alloyed nanowires (NW) were obtained by the matrix synthesis method: the effect of the
growth voltage and the effect of using a reference electrode were studied. It is shown that the composition of
FeNi nanowires strongly depends on the growth potential (with its increase, the bcc structure is changing into
fcc), and it is also ...

Added: November 12, 2021

Panina I., Balandin S., Tsarev A. et al., International Journal of Molecular Sciences 2023 Vol. 24 No. 2 P. 1

To date, a number of lantibiotics have been shown to use lipid II — a highly conserved peptidoglycan precursor in the cytoplasmic membrane of bacteria — as their molecular target. The α-component (Lchα) of the two-component lantibiotic lichenicidin (Lchα), previously isolated from the Bacillus licheniformis VK21 strain, seems to contain two putative lipid II binding ...

Added: February 21, 2023

Alfimov M., Litvinov A., Journal of High Energy Physics 2022 No. 01 Article 43

We study regularization scheme dependence of beta-function for sigma models with two-dimensional target space. Working within four-loop approximation, we conjecture the scheme in which the beta-function retains only two tensor structures up to certain terms containing zeta_3. Using this scheme, we provide explicit solutions to RG flow equation corresponding to Yang-Baxter- and lambda-deformed SU(2)/U(1) sigma ...

Added: February 1, 2022

Kuzmichev S. A., Kuzmicheva T. E., Tchesnokov S. N. et al., Journal of Superconductivity and Novel Magnetism 2016 Vol. 29 No. 4 P. 1111-1116

We present temperature dependences of the large and the small superconducting gaps measured directly by SnS-Andreev spectroscopy in various Fe-based superconductors and MgB2. The experimental L,S(T ) are wellfitted with a two-gap model based on Moskalenko and Suhl system of equations (supplemented with a BCS integral renormalization). From the fitting procedure, we estimate the key ...

Added: March 19, 2016

Min Namkung, Younghun K., Scientific Reports 2018 Vol. 8 No. 1 P. 16915-1-16915-18

Sequential state discrimination is a strategy for quantum state discrimination of a sender’s quantum
states when N receivers are separately located. In this report, we propose optical designs that can
perform sequential state discrimination of two coherent states. For this purpose, we consider not
only binary phase-shifting-key (BPSK) signals but also general coherent states, with arbitrary prior
probabilities. Since ...

Added: November 16, 2020

Orekhov M., Russian Journal of Physical Chemistry A 2021 Vol. 95 P. 2059-2064

Molecular dynamic models are created for properties of bivalent ions in organic solvents. It is shown that molecules of the considered solvents bound to ions via oxygen atoms. A theoretical model is developed that describes the ion coordination number. The coordination number in this model is determined by the ratio between the sizes of the ...

Added: October 14, 2021