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Quantum Communications and Quantum Imaging

Verification of quantum entanglement of two-mode squeezed light source towards quantum radar and imaging

Genta Masada

Published Aug 30, 2017• 5 citations
Publisher

Abstract

Two-mode squeezed light is an effective resource for quantum entanglement and shows a non-classical correlation between each optical mode. We are developing a two-mode squeezed light source to explore the possibility of quantum radar based on the quantum illumination theory. It is expected that the error probability for discrimination of target presence or absence is improved even in a lossy and noisy environment. We are also expecting to apply two-mode squeezed light source to quantum imaging. In this work we generated two-mode squeezed light and verify its quantum entanglement property towards quantum radar and imaging. Firstly we generated two independent single-mode squeezed light beams utilizing two sub-threshold optical parametric oscillators which include periodically-polled potassium titanyl phosphate crystals for the second order nonlinear interaction. Two single-mode squeezed light beams are combined using a half mirror with the relative optical phase of 90◦ between each optical field. Then entangled two-mode squeezed light beams can be generated. We observes correlation variances between quadrature phase amplitudes in entangled two-mode fields by balanced homodyne measurement. Finally we verified quantum entanglement property of two-mode squeezed light source based on Duan’s and Simon’s inseparability criterion.

DOI
10.1117/12.2273585

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Two-mode squeezed light is an effective resource for quantum entanglement and shows a non-classical correlation between each optical mode. We are developing a two-mode squeezed light source to explore the possibility of quantum radar based on the quantum illumination theory. It is expected that the error probability for discrimination of target presence or absence is improved even in a lossy and noisy environment. We are also expecting to apply two-mode squeezed light source to quantum imaging. In this work we generated two-mode squeezed light and verify its quantum entanglement property towards quantum radar and imaging. Firstly we generated two independent single-mode squeezed light beams utilizing two sub-threshold optical parametric oscillators which include periodically-polled potassium titanyl phosphate crystals for the second order nonlinear interaction. Two single-mode squeezed light beams are combined using a half mirror with the relative optical phase of 90◦ between each optical field. Then entangled two-mode squeezed light beams can be generated. We observes correlation variances between quadrature phase amplitudes in entangled two-mode fields by balanced homodyne measurement. Finally we verified quantum entanglement property of two-mode squeezed light source based on Duan’s and Simon’s inseparability criterion.
Two-mode squeezed light is a macroscopic quantum entangled state of electro-magnetic fields and shows non-classical correlation between quadrature phase amplitudes in each optical mode. In this work the author is developing a high-quality two-mode squeezed light source for exploring the possibility of a quantum radar system based on a quantum illumination method and also expecting to apply it to quantum imaging. Two-mode squeezed light can be generated by combining two independent single-mode squeezed light beams using a beam splitter with a relative optical phase of 90 degrees between them. In current experimental progress the author developed two sub-threshold optical parametric oscillators to generate single-mode squeezed light beams. In the actual quantum radar or quantum imaging system, a turbulent atmosphere degrades quantum entanglement of a light source and affects performance of target detection. An optical loss is one of the simplest and most probable examples of environmental factors. In this work an evaluation method for quantum entanglement of two-mode squeezed light source is developed with consideration for the optical loss based on Duan's inseparability criteria.
We started to research quantum illumination radar and quantum imaging by utilizing high quality continuous-wave two-mode squeezed light source as a quantum entanglement resource. Two-mode squeezed light is a macroscopic quantum entangled state of the electro-magnetic field and shows strong correlation between quadrature phase amplitudes of each optical field. One of the most effective methods to generate two-mode squeezed light is combining two independent single-mode squeezed lights by using a beam splitter with relative phase of 90 degrees between each optical field. As a first stage of our work we are developing two-mode squeezed light source for exploring the possibility of quantum illumination radar and quantum imaging. In this article we introduce current development of experimental investigation of single-mode squeezed light. We utilize a sub-threshold optical parametric oscillator with bow-tie configuration which includes a periodically-polled potassium titanyl phosphate crystal as a nonlinear optical medium. We observed the noise level of squeezed quadrature −3.08±0.13 dB and anti-squeezed quadrature at 9.29±0.13 dB, respectively. We also demonstrated the remote tuning of squeezing level of the light source which leads to the technology for tuning the quantum entanglement in order to adapt to the actual environmental condition.
We started to research quantum radar based on a quantum illumination method by utilizing continuous-wave two-mode squeezed light as a quantum entanglement resource. Two-mode squeezed light is a macroscopic quantum entangled state of electro-magnetic fields and shows a property of non-classical correlation between quadrature phase amplitudes of each optical field. One of the most effective methods to generate two-mode squeezed light is combining two independent single-mode squeezed light beams by using a beam splitter. As a first step of our work we introduce current development of a single-mode squeezed light source and construction of a balanced homodyne detection part. We utilized a sub-threshold optical parametric oscillator to generate squeezed light and observed the noise level of squeezed quadrature at －3.08±0.13 dB and anti-squeezed quadrature at 9.29±0.13 dB by balanced homodyne measurement.
Quantum illumination is an attractive scheme for target detection utilizing quantum entanglement to improve error probability of discrimination for target presence or absence even in a lossy and noisy environment. In the quantum illumination with two-mode squeezed vacuum states, one of the entangled beams, a signal beam is transmitted towards a lossy optical medium. And the other beam, a reference beam is directly sent to receiver with a lossless channel. So, the entangled light beams are affected by the asymmetric optical loss. In this work we calculate the correlation variance of quadrature phase amplitudes of two-mode squeezed light under the asymmetric optical-loss conditions and discuss its non-classical correlation based on Duan’s and Simon’s inseparability criterion. The asymmetric optical loss sensitively increases the correlation variance and violates the inseparability criterion. In this work we consider asymmetric two-mode squeezed light as an initial state where the signal beam has larger quadrature phase amplitudes than the reference beam. After exposition to the asymmetric optical loss only the quadrature phase amplitudes of the signal beam is attenuated and become comparable to those of the reference beam. As a result it is expected that the asymmetric two-mode squeezed light has an ability to compensate the effect of the asymmetric optical loss and can maintain the inseparability criterion in the sense of Duan and Simon.
Squeezed light is a nonclassical state of electro-magnetic field and has noise suppressed below the standard quantum limit in one quadrature component while increased in the other. One of the important applications of squeezed lights is quantum enhanced sensing such as gravitational wave detector with ultimate resolution. Another important application is continuous variables quantum teleportation which utilizes two mode squeezed lights as an essential resource for quantum entanglement. In these applications the final outcome is limited by squeezing level. So it is important to generate highly squeezed light. Over the past few decades a considerable number of the experiments have been performed to generate highly squeezed lights. One of the successful methods is utilization of a sub-threshold optical parametric oscillator (OPO) which includes a nonlinear optical crystal. In this article we will introduce current development of experimental investigation of continuous-wave highly squeezed light by utilizing the OPO and current topics about applications of squeezed light.
Abstract In this study, we explore the theoretical application of entangled multi-mode squeezed light for label-free optical super-resolution imaging. By generating massively entangled multi-mode squeezed light through an array of balanced beam splitters, using a single-mode squeezed light input, we create a multi-mode quantum light state with exceptional entanglement and noise suppression below the shot noise level. This significantly reduces imaging measurement errors compared to classical coherent state light imaging when the same number of photons are used on the imaging sample. We demonstrate how to optimize the imaging system’s parameters to achieve the Heisenberg imaging error limit, taking into account the number of entangled modes and photons used. We also examine the effects of optical losses in the imaging system, necessitating adjustments to the optimized parameters based on the degree of optical loss. In practical applications, this new quantum imaging approach reduces the number of photons needed to achieve the same image quality by two orders of magnitude compared to classical imaging methods that use non-entangled, non-squeezed coherent state light.