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Molecular Crystals and Liquid Crystals

Extremely weak optical phase control and photon statistical analysis using liquid crystal devices

Akira Terazawa, Hiroyuki Okada

Published Mar 13, 2026• 0 citations
Publisher

Abstract

Variation in extremely-weak photon counts with changing gate time was investigated using a Mach–Zehnder interferometer and a liquid crystal (LC) device. The number of photon counts per unit time of measurement was miniaturized, and changes in the discrete counts were observed by changing the gate time. In addition, changing the voltage applied to the LC device confirmed that the average photon count in the extremely weak light state can be treated statistically and changes according to the Poisson distribution. This indicates that the photons flew independently. This phenomenon is considered a promising simple variable photon light source for Boson sampling.

DOI
10.1080/15421406.2026.2642358

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Variation in extremely-weak photon counts with changing gate time was investigated using a Mach–Zehnder interferometer and a liquid crystal (LC) device. The number of photon counts per unit time of measurement was miniaturized, and changes in the discrete counts were observed by changing the gate time. In addition, changing the voltage applied to the LC device confirmed that the average photon count in the extremely weak light state can be treated statistically and changes according to the Poisson distribution. This indicates that the photons flew independently. This phenomenon is considered a promising simple variable photon light source for Boson sampling.
Abstract We have evaluated a number of photon modulations using a Mach–Zehnder interferometer combined with a surface-stabilized ferroelectric liquid crystal (SSFLC) device for optical phase control. By varying the applied voltage to the SSFLC, a clear change in the detected number of photons was observed. Statistical analysis of the photon counts revealed that the weak optical field followed the Poisson distributions with two distinct mean numbers of photons, corresponding to the two voltage-induced states of the SSFLC. This result suggests the probabilistic nature of independently emitted laser photons and demonstrates that such discrete photon statistics can be achieved via binary voltage control of the SSFLC.
Abstract A Mach–Zehnder interferometer with an optical phase control by a twisted nematic (TN) liquid crystal (LC) device was studied. In a typical TN LC device, a change in the optical rotation state of π/2 can be obtained by applying a voltage of about 5 V with a cell thickness of several-micron. The TN cell is inserted into one optical path in the Mach–Zehnder interferometer. We obtained a pattern change when voltage was applied to the LC cell due to the change of the optical interference state. As a result, a change in the number of photons under weak light conditions is observed.
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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.
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.