Quantum super-resolution imaging provides a nonlabeling method to surpass the diffraction limit of imaging systems. This technique relies on measurement of the second-order correlation function and usually employs spatially entangled photon sources. We introduce recent methods that achieve spatial resolution enhancement through quantum approaches, particularly the imaging techniques utilizing biphoton states. The fundamental mechanisms are discussed in detail to explain why biphoton states enable super-resolution. Additionally, we introduce multiple algorithms that extract the correlation function from the readings of two-dimensional detectors. Several cases are reviewed to evaluate the advantages and prospects of quantum imaging, along with a discussion of practical developments and potential applications.
Quantum super-resolution imaging provides a nonlabeling method to surpass the diffraction limit of imaging systems. This technique relies on measurement of the second-order correlation function and usually employs spatially entangled photon sources. We introduce recent methods that achieve spatial resolution enhancement through quantum approaches, particularly the imaging techniques utilizing biphoton states. The fundamental mechanisms are discussed in detail to explain why biphoton states enable super-resolution. Additionally, we introduce multiple algorithms that extract the correlation function from the readings of two-dimensional detectors. Several cases are reviewed to evaluate the advantages and prospects of quantum imaging, along with a discussion of practical developments and potential applications.
Quantum imaging emerged quite recently as a breakthrough technology of overcoming the diffraction limit in microscopy and enhancement of optical resolution without the necessity to use hard radiation or perform scanning in the near field [1] , [2] . Both, the quantum imaging itself and the more “classical” techniques inspired by it (for example, super-resolution optical fluctuations imaging – SOFI [3] ), rely on detection and analysis of photon (intensity) correlations. Typically, it is believed that the more correlated illuminating light is used and the higher order of the correlations is measured, the larger super-resolution can be achieved. That conclusion is based on efficient narrowing of the point-spread function, which, however, does not necessarily imply better resolution as the ability to reconstruct smaller features of the investigated object successfully.
ABSTRACT Sources of light characterized by a well‐defined number of photons are widely used in quantum experiments and technologies due to their peculiar properties, which include sub‐Poissonian statistics, spatial, temporal, and frequency correlations, as well as maximal and high‐dimensional entanglement. Searching for the best experimental approaches that allow us to visualize the quantum state of two (or more) photons has been a long‐standing fundamental question, which has been mainly addressed via mode projection techniques. The rapid development of single‐photon‐sensitive cameras, however, has opened the pathway to conceptually simple, yet faster and more efficient, measurement techniques. This review explores the latest advancements in measuring the spatial structure of the quantum state of light using 3D imaging techniques. An overview of the most used single‐photon camera technologies is given, highlighting their differences and respective advantages. Besides the fundamental interest in reconstructing experimentally one of the most mysterious concepts of microscopic physics, this review illustrates how the techniques developed in this direction can lead to new ideas in the fields of imaging and sensing, for instance, superresolution measurements and phase‐enhanced and sub‐shot noise imaging.
The spatial resolution of an optical system is limited by diffraction. Various schemes have been proposed to achieve resolution enhancement by employing either a scanning source/detector configuration or a two-photon response of the object. Here, we experimentally demonstrate a full-field resolution-enhancing scheme, based on the centroid estimation of spatially quantum-correlated biphotons. Our standard-quantum-limited scheme is able to image a general non-fluorescing object, using low-energy and low-intensity infrared illumination (i.e., with <0.001 photon per pixel per frame at 710 nm), achieving 41% of the theoretically available resolution enhancement. Images of real-world objects are shown for visual comparison, in which the classically bound resolution is surpassed using our technically straightforward quantum-imaging scheme.
Classically, the angular resolution of a telescope is limited by its diffraction limit: the ratio of its observing wavelength to its diameter. Developments in quantum information theory over the past decade have uncovered quantum-optimal measurement methods that enable super-resolution imaging beyond the diffraction limit, and many laboratory-scale demonstrations of these methods have been performed over the past decade, culminating in the recent first on-sky demonstration of quantum-enhanced astronomical imaging. In this Review, we detail the current progress and achievements of these theoretical and experimental results, discuss the astronomical science cases motivating the development of higher resolution telescopes, summarise the technological challenges facing the practical application of quantum imaging technologies to astronomy, and present a vision for the realization of \emph{quantum telescopes} with imaging resolutions orders of magnitude better than current observatories.
Quantum imaging is an emerging field based on quantum mechanics and imaging technology, capable of unique capabilities in resolution, sensitivity, and information processing. An extensive review of the concepts, methods, and uses of quantum imaging is given in this chapter. The main ideas of quantum mechanics that are relevant to imaging, including superposition, entanglement, and quantum measurement, are introduced in this chapter. Following this, the various quantum imaging techniques, including quantum entanglement imaging, ghost imaging, and quantum lithography, illuminating their operational mechanisms and advantages over classical methods, are explored. The role of advanced photonic systems, single-photon detectors, and quantum dots in enhancing image quality are discussed. Additionally, the incorporation of quantum computing and machine learning with quantum imaging is examined, highlighting how these interdisciplinary approaches are pushing the boundaries of what can be visualized and analysed. Quantum imaging applications are varied, groundbreaking, and innovative, ranging from medical diagnostics and biological imaging to quantum communication and fundamental physics research. By harnessing the exclusive properties of quantum states, these applications achieve higher precision and new capabilities that classical imaging techniques cannot match. The challenges and future directions of quantum imaging, considering both the technical hurdles and the potential for groundbreaking discoveries, are discussed as well. In a nutshell, the chapter aims to offer the readers an in-depth insight into quantum imaging, its current state, and its future prospects by providing a holistic view of how quantum imaging is composed to revolutionize various scientific and technological fields.
One of the most surprising consequences of quantum mechanics is the entanglement of two or more distant particles. Although questions regarding fundamental issues of quantum theory still exist, quantum entanglement has started to play important roles in practical engineering applications. Quantum imaging is one of these exciting areas. Quantum imaging has demonstrated two peculiar features: 1) reproducing ghost images in a nonlocal manner and 2) enhancing the spatial resolution of imaging beyond the diffraction limit. In this paper, we start with the review of classical imaging to establish the basic concepts and formalisms of imaging. We then analyze two-photon imaging with particular emphasis on the physics of spatial resolution enhancement and the ghost imaging phenomenon.