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Journal of Experimental and Theoretical Physics

Model of Optical Solitons in Liquid Crystals

Victor Vasilyevich Belyaev, T. F. Kamalov, Yu. T. Kamalov, Andrey D. Latipov

Published Jun 1, 2025• 1 citation
Publisher

Abstract

Abstract The conditions of soliton formation in a liquid crystal layer for generation of a pair of photons in an entangled quantum state (biphotons) during quantum calculations are considered. The geometrical dimensions of the soliton generated by a pulse of optical radiation, its dynamics and stability are estimated by using the knowledge of the liquid crystal physical parameters as well as its non-linear optical properties. The possibility of overlapping of optical solitons neighboring in space or time (or regions inside the liquid crystal layer, in which the deformation induced by the light wave field from successive light pulses occurs) is considered. In nematic liquid crystals (LCs), it is possible to obtain single solitons with spatial size of several tens of micrometers and less, the formation time from fractions of a millisecond to tens of milliseconds, and the existence time from fractions of the millisecond to hundreds of milliseconds. On this basis, it is possible to “encode” entangled states with a high level of signal distinction and to carry out quantum calculations.

DOI
10.1134/s1063776125700062

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Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE•Apr 1, 1991•0 citations
Abstract The conditions of soliton formation in a liquid crystal layer for generation of a pair of photons in an entangled quantum state (biphotons) during quantum calculations are considered. The geometrical dimensions of the soliton generated by a pulse of optical radiation, its dynamics and stability are estimated by using the knowledge of the liquid crystal physical parameters as well as its non-linear optical properties. The possibility of overlapping of optical solitons neighboring in space or time (or regions inside the liquid crystal layer, in which the deformation induced by the light wave field from successive light pulses occurs) is considered. In nematic liquid crystals (LCs), it is possible to obtain single solitons with spatial size of several tens of micrometers and less, the formation time from fractions of a millisecond to tens of milliseconds, and the existence time from fractions of the millisecond to hundreds of milliseconds. On this basis, it is possible to “encode” entangled states with a high level of signal distinction and to carry out quantum calculations.
It is an urgent task to create reliable, cost‐effective, simple in technology elements for performing quantum computing with qubits based on pairs of photons having entangled polarizations. The conditions of soliton formation in a liquid crystal (LC) layer for generation of a pair of photons in an entangled quantum state (biphotons) during quantum calculations are considered. The geometrical dimensions of the soliton generated by a pulse of optical radiation, its dynamics and stability are estimated. Besides, propagation of both extraordinary and ordinary rays in the nematic LC with different boundary conditions is calculated. The paper is a demonstration of using display technologies and science for new generation of optical processing tasks. From another side, quantum computing can be used also in images processing for the tasks of display picture rendering.
The features of the propagation of optical solitons in a dielectric are currently actively being applied in the fields of applied use of quantum phenomena. When creating new technologies based on the theory of solitons, the topical issue arises of developing soliton models accessible for practical implementation, suitable for subsequent modelling of real entangled systems. We chose a nematic liquid crystal as a dielectric medium for considering optical 1D envelopes of solitons. On the basis of a mathematical model of the behaviour of a pair of entangled solitons in a medium, a special stochastic representation of the wave function is constructed for subsequent modelling of entangled states of photons. Based on a qualitative analysis, a constructive addition to the entangled photon detector is proposed. The complete replacement of classical elements is discussed with a view to the possible use of the idea in the creation of quantum computers.
Abstract Liquid crystals, with their ability to self-assemble, strong response to an electric field and integrability into complex systems, are key materials in light-beam manipulation 1 . The recently discovered ferroelectric nematic liquid crystals 2,3 also have considerable second-order optical nonlinearity, making them a potential material for nonlinear optics 4,5 . Their use as sources of quantum light could considerably extend the boundaries of photonic quantum technologies 6 . However, spontaneous parametric down-conversion, the basic source of entangled photons 7 , heralded single photons 8 and squeezed light 9 , has so far not been observed in liquid crystals—or in any liquids or organic materials. Here we implement spontaneous parametric down-conversion in a ferroelectric nematic liquid crystal and demonstrate electric-field tunable broadband generation of entangled photons, with an efficiency comparable to that of the best nonlinear crystals. The emission rate and polarization state of photon pairs is markedly varied by applying a few volts or twisting the molecular orientation along the sample. A liquid-crystal source enables a special type of quasi-phase matching 10 , which is based on the molecular twist structure and is therefore reconfigurable for the desired spectral and polarization properties of photon pairs. Such sources promise to outperform standard nonlinear optical materials in terms of functionality, brightness and the tunability of the generated quantum state. The concepts developed here can be extended to complex topological structures, macroscopic devices and multi-pixel tunable quantum light sources.
Entangled photon pair sources relying on spontaneous parametric down-conversion (SPDC) are an essential ingredient for optical quantum technologies. Currently, the vast majority of SPDC sources is based on solid-state crystals. However, their rigid nature implies a careful design of the source as well as it limits the two-photon state that can be generated, without much possibility of tuning it. Here, we demonstrate a new generation of efficient, highly tunable sources of entangled photons based on recently discovered liquid crystal materials called ferroelectric nematic liquid crystals (FNLC). In addition to other highly desirable properties that liquid crystals possess, such as the ability to self-assemble into complex structures, strong response to the electric field and integrability into complex optical systems, FNLCs also possess considerable optical nonlinearity. This, as we demonstrate, enables also efficient SPDC generation and opens the door for promising new functionalities in quantum technologies. This work demonstrates the first-ever realization of SPDC in soft, organic matter, with the possibility of controlling the molecular order and thus tuning the two-photon polarization state. We show that almost any polarization state can be generated by simply adjusting the twist of the molecular orientation along the sample. Additionally, by applying only a few volts, we can drastically alter both the emission rate and the generated state of photon pairs, which enables real-time tunability. Developed concepts could lead to complex multi-pixel devices generating quantum light with real time tunability and therefore hold the potential to have a huge impact in the field of quantum technologies.
We present here our results on using liquid crystals (LCs) in experiments with nonclassical light sources: (1) single-photon sources exhibiting antibunching (separation of all photons in time), which are key components for secure quantum communication systems and (2) entangled photon source with photons exhibiting quantum interference in a Hong–Ou–Mandel interferometer. In the first part, both nematic and cholesteric liquid crystal (CLC) hosts were used to create definite linear or circular polarization of antibunched photons emitted by different types of single emitters (dye molecules, nanocrystal quantum dots (NQDs), nanodiamonds with color centers, etc.). If the photon has unknown polarization, filtering it through a polarizer to produce the desired polarization for quantum key distribution with bits based on polarization states of photons will reduce by half the efficiency of a quantum cryptography system. In the first part, we also provide our results on observation of a circular polarized microcavity resonance in NQD fluorescence in a 1-D chiral photonic bandgap CLC microcavity. In the second part of this paper with indistinguishable, time-entangled photons, we demonstrate our experimental results on simulating quantum mechanical barrier tunneling phenomena. A Hong–Ou–Mandel dip (quantum interference effect) is shifted when a phase change was introduced on the way of one of entangled photons in pair (one arm of the interferometer) by inserting in this arm an electrically controlled planar-aligned nematic LC layer between two prisms in the conditions close to a frustrated total internal reflection. By applying different AC-voltages to the planar-aligned nematic layer and changing its refractive index, we can obtain various conditions for incident photon propagation – from total reflection to total transmission. Measuring changes of tunneling times of photon through this structure with femtosecond resolution permitted us to answer some unresolved questions in quantum mechanical barrier tunneling phenomena.
Laser-induced bulk gratings and temporal instabilities of nonlinear wave processes with different components of light polarization have been studied in the liquid crystals (LC). A mirrorless feedback arises because of the non-local nonlinear response of an anisotropic elastic medium on the external field. The multiplicative nature of the molecular fluctuations in the LC under external field are discussed and the light-induced reorientation effects in this medium can be considered as a noise-induced phase transition. . The quantum aspects of behavior of the radiation fluctuations for passing through the LC light are considered. A new method of formation of quantum states of the light in the linear system at dynamic diffraction is discussed for the first time. The squeezed states of the field and the photon superbunching are obtained for two geometries (Bragg and Laue) of diffraction in spatially periodic medium. The approach gives a new opportunities for a verification of quantum properties of the light in experiment.