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International Workshop on Active-Matrix Flatpanel Displays and Devices

Analysis of Liquid Crystal Optical Switching Devices Aimed at Quantum Computing

Hiroyuki Okada

Published Jul 2, 2024• 0 citations
Publisher

Abstract

In order to realize the ultimate goal of developing universal photon quantum circuits using liquid crystals, we have numerically analyzed the transmission and reflection of photons in a 4× 4 matrix method for an optical switching device, and clarified the possibility of applying interference light to quantum circuits. The results showed that switching between reflection and entangled states was possible at an incident angle of 86° with homogeneous orientation and HOM interference condition. Very small amplitude of photon analysis was also carried out to analyze the symmetry of the properties based on the uncertainty quantities.

DOI
10.23919/am-fpd61635.2024.10615867

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In order to realize the ultimate goal of developing universal photon quantum circuits using liquid crystals, we have numerically analyzed the transmission and reflection of photons in a 4× 4 matrix method for an optical switching device, and clarified the possibility of applying interference light to quantum circuits. The results showed that switching between reflection and entangled states was possible at an incident angle of 86° with homogeneous orientation and HOM interference condition. Very small amplitude of photon analysis was also carried out to analyze the symmetry of the properties based on the uncertainty quantities.
We present here our results on using liquid crystals 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, cholesteric liquid crystal hosts were used to create definite circular polarization of antibunched photons emitted by nanocrystal quantum dots. 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 nanocrystal quantum dot fluorescence in a 1-D chiral photonic bandgap cholesteric liquid crystal microcavity. In the second part of this paper with indistinguishable, time-entangled photons, we demonstrate our experimental results on simulating quantum-mechanical barrier tunnelling 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 liquid crystal 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 tunnelling times of photon through this structure with femtosecond resolution permitted us to answer some unresolved questions in quantum-mechanical barrier tunnelling phenomena.
Four-bit input linear quantum computing with liquid crystal (LC) devices was studied using the Deutsch–Jozsa algorithm. A laser beam is split into four paths and passed through a configuration of twisted nematic (TN) LC device/(λ/2 waveplate)/TN LC device for computation. In order to minimize the effect of photon loss in the light path, a 4 × 4 matrix analysis was done for optimization. We fabricated a prototype for four optical-path linear quantum computing. As a result, we obtained changes in the number of photons counting according to Deutsch–Jozsa’s algorithm under the extremely weak light state.
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.
Abstract A basic experiment on 2-bit quantum calculations related to the Deutsch–Jozsa algorithm on a linear optical quantum computer using a liquid crystal (LC) device as a linear optical element was investigated. By controlling the phase of each of the two split laser beams and checking the number of photons at the output, it is possible to determine if the input bits are “not equal” or “not uniform.” The phase of the laser light was controlled using an LC device and a half-wave plate, and changes in the interference state of the output light and the number of photons were observed. The voltage application to the LC device is set at the input bit. As a result, the interference state changed according to the input bit, and changes in the number of photons were observed.
We review recent research in various types of optical quantum computing using liquid crystal devices. First, we have investigated Young’s Interference experiment using self-aligned liquid crystal (LC) devices and a logical “NOT” operation is achieved. Second, numerical quantization of interfering small photons using an LC retarder is investigated. Third, a Mach–Zehnder interferometer with an optical phase control by a twisted nematic (TN) LC device was studied. Fourth, a basic experiment on 2-bit quantum calculations related to the Deutsch-Jozsa algorithm on a linear optical quantum computer using the LC device as a linear optical element was investigated.
We review recent research in various types of optical quantum computing using liquid crystal (LC) devices. First, we have investigated Young's Interference experiment using self-aligned LC devices and a logical “NOT” operation is achieved. Second, numerical quantization of interfering small photons using a LC retarder is investigated. Third, a Mach-Zehnder interferometer with an optical phase control by a twisted nematic (TN) LC device was studied. Fourth, 4-bit optical path linear quantum computation using Deutsch-Jozsa algorithm with the LC device as a linear optical element was investigated.