Quantum image distillation aims to extract the signal image from a mixture of the signal and noise images that are indistinguishable in terms of spectrum and polarization, a process that is unachievable with classical methods. However, in contrast to the amplitude image, phase distillation is challenging via direct spatial or temporal correlation of photon pairs. Incorporating with the polarization entanglement of photon pairs, it is demonstrated here that the phase signal can be quickly distilled by using an integrated computing metasurface to solve the Poisson equation. The proposed technique remains robust even with noise levels two orders higher than the signal, with potential applications in quantum communication and cryptography. Based on the present scheme, it also enables the measurement of photon wave function and the achievement of noninterferometric quantum-enhanced quantitative phase imaging. Our work involving the integrated-metasurface analogue computing paves the way for advancing efficient and rapid quantum information and image processing.
Quantum image distillation aims to extract the signal image from a mixture of the signal and noise images that are indistinguishable in terms of spectrum and polarization, a process that is unachievable with classical methods. However, in contrast to the amplitude image, phase distillation is challenging via direct spatial or temporal correlation of photon pairs. Incorporating with the polarization entanglement of photon pairs, it is demonstrated here that the phase signal can be quickly distilled by using an integrated computing metasurface to solve the Poisson equation. The proposed technique remains robust even with noise levels two orders higher than the signal, with potential applications in quantum communication and cryptography. Based on the present scheme, it also enables the measurement of photon wave function and the achievement of noninterferometric quantum-enhanced quantitative phase imaging. Our work involving the integrated-metasurface analogue computing paves the way for advancing efficient and rapid quantum information and image processing.
Phase reconstruction plays a pivotal role in biology, medical imaging, and wavefront sensing. However, multiple measurements and adjustments are usually required for conventional schemes, which inevitably reduces the quality of phase imaging. Here, based on multi-channel metasurface and quantum entanglement source, a simple and integrated quantum analog operation system is proposed to realize quantitative phase reconstruction with a high signal-to-noise ratio (SNR) under a low signal photon level. Without additional measurements and adjustments, four differential images necessary for the phase reconstruction are captured simultaneously. The non-local correlation of entangled photon pairs enables to remotely manipulate working modes of the system. Besides, the consistency of entangled photon pairs in time domain makes it possible to achieve a high SNR imaging by trigger detection. The results may potentially empower the application of metasurfaces in optical chip, wave function reconstruction, and label-free biology imaging.
Phase contrast microscopy is essential in optical imaging, but traditional systems are bulky and limited by single-phase modulation, hindering visualization of complex specimens.Metasurfaces, with their subwavelength structures, offer compact integration and versatile light field control.Quantum imaging further enhances performance by leveraging nonclassical photon correlations to suppress classical noise, improve contrast, and enable multifunctional processing.Here, we report, a dual-mode bright-dark phase contrast imaging scheme enabled by quantum metasurface synergy.By combining polarization entanglement from quantum light sources with metasurface phase modulation, our method achieves highcontrast, adaptive bright-dark phase contrast imaging of transparent samples with arbitrary phase distributions under low-light conditions.Compared to classical weak light imaging, quantum illumination suppresses environmental noise at equivalent photon flux, improving the contrast from 0.22 to 0.81.Moreover, quantum polarization entanglement enables remote switching to ensure high-contrast imaging in at least one mode, supporting dynamic observation of biological cells with complex phase structures.This capability is especially valuable in scenarios where physical intervention is difficult, such as in miniaturized systems, in vivo platforms, or extreme environments.Overall, the proposed scheme offers an efficient noninvasive solution for biomedical imaging with strong potential in life science applications.
Quantum phase imaging enables the analysis of transparent samples with thickness and refractive index variations in scenarios requiring precise measurements under low-light conditions. Here, we present a compact quantum phase-gradient imaging system integrating a lithium niobate (LiNbO3) metasurface for generating spatially entangled photon pairs and a silicon (Si) metasurface for phase gradient extraction. By leveraging nonlocal resonances, the LiNbO3 metasurface enables efficient spontaneous parametric down-conversion (SPDC) with all-optically angularly tunable emission, while the Si metasurface provides a nearly linear optical transfer function (OTF) that differentiates the photon wavefunction and extracts phase gradients.Experimental proof-of-concept results demonstrate the imaging of up to 25~rad/mm phase gradients, achieving 89% similarity with the reference values. The pixel resolution of the system can be potentially enhanced by orders of magnitude by increasing the metasurface dimensions and resonance quality factor.Our work showcases the application of metasurfaces in both generating and detecting quantum states and establishes a new paradigm for portable quantum phase-gradient imaging, with potential applications in quantum sensing, microscopy, and LiDAR technology.
Quantum imaging using entangled photon pairs from spontaneous parametric down-conversion (SPDC) provides fundamental advantages over classical phase imaging in the study of transparent object, such as the operation at ultra-low photon flux and high signal-to-noise ratio [1], [2]. Metasurfaces supporting angle-dependent resonances have recently been employed to achieve phase imaging by extracting phase gradients of incident light [3]. These nanoscale metasurfaces indicate significant potential to replace bulky differential interference contrast microscopes, offering an opportunity for integration into ultra-compact biomedical devices. Together with recent development on metasurface-based quantum light source, this opens up the potential for developing a compact quantum phase imaging device, where metasurfaces serve both generation and detection functions.
Quantum imaging has non-negligible advantages in terms of sensitivity, signal-to-noise ratio, and novel imaging schemes. Based on metasurfaces, the information density and stability of the quantum imaging system can be further improved. Here we experimentally demonstrate that two patterns, simultaneously and independently superimposed on a high-efficiency dielectric metasurface, can be remotely switched via polarization-entangled photon pairs. Furthermore, using the time-correlated property of entangled photon pairs, the information carried by quantum light can be remarkably discriminated from background noise. This work confirms that the phase manipulation of quantum light with metasurfaces has a huge potential in the field of quantum imaging, quantum state tomography, and also promises real-world quantum metasurface devices.
Quantum-enhanced optical sensing leverages correlations and entanglement in multiphoton states to surpass the limitations of classical measurement. However, the widespread deployment of quantum imaging and polarimetry has been hindered by bulky nonlinear crystals, alignment-sensitive free-space optics, and limited control over the spatial and polarization structure of quantum light. This thesis investigates how engineered nanophotonic metasurfaces, together with two-photon probing schemes, can overcome these constraints and enable compact, versatile, and high-performance quantum sensing platforms. The first component of the thesis introduces a metasurface-enabled quantum imaging system based on spatially entangled photon pairs generated from a subwavelength-thick lithium niobate (LiNbO3) nonlinear metasurface. Exploiting nonlocal guided-mode resonances with strong angular dispersion, the system realizes a hybrid imaging protocol that combines quantum ghost imaging with all-optical wavelength-controlled scanning. A theoretical framework linking momentum-space biphoton correlations to image formation is developed, including the effects of pump-beam waist and metasurface quality factor. Numerical simulations and proof-of-principle experiments demonstrate 2D imaging with strong contrast and establish that metasurface-based photon-pair sources can achieve fields of view and resolution-cell counts far beyond what is possible with bulk-crystal SPDC. Building on this platform, the thesis presents the first quantum phase imaging system that integrates metasurfaces for both photon-pair generation and phase-gradient detection. A silicon (Si) metasurface with a near-linear optical transfer function directly maps phase gradients of transparent samples into spatial quantum correlations, eliminating the need for interferometers or long propagation paths. Experiments show that phase gradients up to 25rad/mm can be retrieved with high fidelity, and the system supports switchable operation between amplitude and phase imaging within a significantly more compact scale. The final component of the thesis develops a two-photon probing quantum polarimetry (TPQP) protocol for characterizing scattering media. By combining Monte Carlo modeling of microscopic photon trajectories with Mueller-matrix decomposition and quantum state tomography, the framework links entanglement degradation to macroscopic polarization observables and resolves ambiguities in Mueller-matrix extraction through tailored probe states. Experiments using tissue-mimicking phantoms confirm that TPQP exhibits significantly higher sensitivity to depolarization than one-photon probing, validating its potential for quantum-enhanced polarimetric sensing and imaging. Overall, this thesis advances quantum optical sensing through two distinct but complementary directions. The first two parts demonstrate how engineered metasurfaces enable compact quantum imaging and phase-gradient detection by integrating photon-pair generation and spatial processing within ultrathin nanophotonic structures. Independently, the two-photon probing quantum polarimetry framework, implemented using a conventional BBO-based entangled source, shows how nonlinear two-photon correlations can enhance sensitivity to depolarization and improve Mueller-matrix reconstruction in scattering media. Although realized on different physical platforms, all components of this work exploit quantum correlations to extract amplitude, phase, and polarization information beyond classical approaches, contributing to the development of practical quantum sensing methodologies.