Quantum imaging holds potential benefits over classical imaging but has faced challenges such as poor signal-to-noise ratios, low resolvable pixel counts, difficulty in imaging biological organisms, and inability to quantify full birefringence properties. Here, we introduce quantum imaging by coincidence from entanglement (ICE), using spatially and polarization-entangled photon pairs to overcome these challenges. With spatial entanglement, ICE offers higher signal-to-noise ratios, greater resolvable pixel counts, and the ability to image biological organisms. With polarization entanglement, ICE provides quantitative quantum birefringence imaging capability, where both the phase retardation and the principal refractive index axis angle of an object can be remotely and instantly quantified without changing the polarization states of the photons incident on the object. Furthermore, ICE enables 25 times greater suppression of stray light than classical imaging. ICE has the potential to pave the way for quantum imaging in diverse fields, such as life sciences and remote sensing.
Quantum imaging holds potential benefits over classical imaging but has faced challenges such as poor signal-to-noise ratios, low resolvable pixel counts, difficulty in imaging biological organisms, and inability to quantify full birefringence properties. Here, we introduce quantum imaging by coincidence from entanglement (ICE), using spatially and polarization-entangled photon pairs to overcome these challenges. With spatial entanglement, ICE offers higher signal-to-noise ratios, greater resolvable pixel counts, and the ability to image biological organisms. With polarization entanglement, ICE provides quantitative quantum birefringence imaging capability, where both the phase retardation and the principal refractive index axis angle of an object can be remotely and instantly quantified without changing the polarization states of the photons incident on the object. Furthermore, ICE enables 25 times greater suppression of stray light than classical imaging. ICE has the potential to pave the way for quantum imaging in diverse fields, such as life sciences and remote sensing.
Entangled photons enable quantum imaging to surpass classical limits in resolution and noise. To address long-standing challenges in quantum imaging (such as low signal-to-noise, limited resolvable pixels, and difficulty imaging biological samples), we present imaging by coincidence from entanglement (ICE). ICE leverages spatial and polarization entanglement to enhance resolution, support biological imaging, and quantify birefringence properties. Polarization entanglement enables remote, quantitative measurement of both phase retardation and principal axis orientation without changing input polarization. ICE achieves up to 25-fold stray light suppression relative to classical imaging. We further introduce wide-field quantum microscopy by coincidence (QMC) using symmetric, balanced paths to achieve Heisenberg-limited super-resolution, with up to 155-fold suppression of stray light and improved speed and contrast-to-noise ratio. Together, QMC and ICE represent significant advances in quantum bioimaging, offering low-light, high-resolution, and noninvasive imaging capabilities with potential impact in life sciences and remote sensing.
Entangled photons have the remarkable ability to be more sensitive to signal and less sensitive to noise than classical light. Joint photons can sample an object collectively, resulting in faster phase accumulation and higher spatial resolution, while common components of noise can be subtracted. Even more, they can accomplish this while physically separate, due to the nonlocal properties of quantum mechanics. Indeed, nearly all quantum optics experiments rely on this separation, using individual point detectors that are scanned to measure coincidence counts and correlations. Scanning, however, is tedious, time consuming, and ill-suited for imaging. Moreover, the separation of beam paths adds complexity to the system while reducing the number of photons available for sampling, and the multiplicity of detectors does not scale well for greater numbers of photons and higher orders of entanglement. We bypass all of these problems here by directly imaging collinear photon pairs with an electron-multiplying CCD camera. We show explicitly the benefits of quantum nonlocality by engineering the spatial entanglement of the illuminating photons and introduce a new method of correlation measurement by converting time-domain coincidence counting into spatial-domain detection of selected pixels. We show that classical transport-of-intensity methods are applicable in the quantum domain and experimentally demonstrate nearly optimal (Heisenberg-limited) phase measurement for the given quantum illumination. The methods show the power of direct imaging and hold much potential for more general types of quantum information processing and control.
With the advancement of non-classical light sources such as single-photon and entangled-photon sources, innovative microscopy based on quantum principles has been proposed for traditional microscopy. This paper introduces the experimental demonstration of a quantum polarization microscopic technique that incorporates a quantum-entangled photon source. Although the point that employs the variation in polarization angle due to reflection or transmission at the sample is similar to classical polarization microscopy, the method for constructing the image contrast is significantly different. The image contrast is constructed by the coincidence count of signal and idler photons. In the case that the coincidence count is recorded from both the signal and idler photons, the photon statistics resemble a thermal state, similar to the blackbody radiation, but with a significantly higher peak intensity in the second-order autocorrelation function at zero delay that is derived from the coincidence count, while, when the coincidence count is taken from either the signal or idler photon only, although the photon state exhibits a thermal state again, the photon statistics become more dispersive and result in a lower peak intensity of the autocorrelation function. These different thermal states can be switched by slightly changing the photon polarization, which is suddenly aroused within a narrow range of the analyzer angle. The autocorrelation function g2(0) at the thermal state exhibits a sensitivity that is three times higher compared to the classical coincidence count rate, and this concept can be effectively utilized to enhance the contrast of the image. One of the key achievements of our proposed method is ensuring a low power of illumination (in the order of Pico-joules) for constructing the image. In addition, the robustness without any precise setup is also favorable for practical use. This polarization microscopic technique can provide a superior imaging technique compared to the classical method, opening a new frontier for research in material sciences, biology, and other fields requiring high-resolution imaging.
With the advancement of non-classical light sources such as single-photon and entangled-photon sources, innovative microscopy based on the quantum principles has been proposed over traditional microscopy. This paper introduces the experimental demonstration of a quantum polarization microscopic technique that incorporates a quantum-entangled photon source. Although the point that employs the variation of polarization angle due to reflection or transmission at the sample is similar to classical polarization microscopy, the method for constructing image contrast is significantly different. Image contrast is constructed by the coincidence count of signal and idler photons. In the case that coincidence count is recorded from both the signal and idler photons, the photon statistics resemble a thermal state, similar to the blackbody radiation, but with a significantly higher peak intensity in the second order autocorrelation function at zero delay that is derived from coincidence count. While, when the coincidence count is taken from either the signal or idler photon only, though the photon state exhibits a thermal state again, the photon statistics become more dispersive and result in a lower peak intensity of the autocorrelation function. These different thermal states can be switched by slightly changing the photon polarization, which is suddenly aroused within narrow range of analyzer angle. This polarization microscopic technique can provide a superior imaging technique compared to the classical method, opening a new frontier for research in material sciences, biology, and other fields requiring high-resolution imaging.
Entangled biphoton sources exhibit nonclassical characteristics and have been applied to imaging techniques such as ghost imaging, quantum holography, and quantum optical coherence tomography. The development of wide-field quantum imaging to date has been hindered by low spatial resolutions, speeds, and contrast-to-noise ratios (CNRs). Here, we present quantum microscopy by coincidence (QMC) with balanced pathlengths, which enables super-resolution imaging at the Heisenberg limit with substantially higher speeds and CNRs than existing wide-field quantum imaging methods. QMC benefits from a configuration with balanced pathlengths, where a pair of entangled photons traversing symmetric paths with balanced optical pathlengths in two arms behave like a single photon with half the wavelength, leading to a two-fold resolution improvement. Concurrently, QMC resists stray light up to 155 times stronger than classical signals. The low intensity and entanglement features of biphotons in QMC promise nondestructive bioimaging. QMC advances quantum imaging to the microscopic level with significant improvements in speed and CNR toward the bioimaging of cancer cells. We experimentally and theoretically prove that the configuration with balanced pathlengths illuminates an avenue for quantum-enhanced coincidence imaging at the Heisenberg limit.
A study published in the international journal Biomedical Optics Express comprehensively demonstrates the potential of quantum imaging techniques using entangled photons to simultaneously achieve minimal invasiveness (non-destructiveness) and extreme precision when observing biological specimens. It argues that illuminating biological specimens with non-classical states of light, such as entangled photon pairs, can physically block uncorrelated classical background noise and exponentially improve the signal-to-noise ratio (SNR). By utilizing quantum correlations and squeezed light states, it transcends the diffraction limit of conventional optical systems, offering unprecedented resolution to visualize delicate biological structures in their natural state. [Quantum Biology Society] Achieving a perfect balance between minimal invasiveness and extreme precision in biological measurements has long been a challenge in the scientific community. Conventional classical optical imaging techniques required intense illumination to obtain high resolution, which inevitably led to cellular damage and ran into the barrier of physical diffraction limits. A recent study published in the international journal Biomedical Optics Express, titled "Application of quantum imaging in biology," comprehensively highlights how quantum imaging technology based on non-classical light breaks through these classical limitations. A joint research team consisting of Hoda Lotfipour, Hassan Sobhani, Mohamad Taghi Dejpasand, and Morteza Sasani Ghamsari from the Photonics and Quantum Technologies Research School at the Nuclear Science and Technology Research Institute (NSTRI) in Tehran, Iran, published this disruptive review study. ■ Quantum Entanglement Perfectly Blocking Noise The researchers focused on the potential of quantum metrology, which introduces non-classical states of light—particularly methods utilizing entangled photon pairs—into biological imaging. When extremely delicate and fragile biological specimens are illuminated with light in entangled quantum states, significant signals can be precisely sorted out through the strong quantum correlations between photons. Through this process, classical background noise that occurs randomly and independently of the entanglement state is physically blocked, ultimately leading to a remarkable, exponential improvement in the system's signal-to-noise ratio (SNR). ■ Extreme Resolution Without Destructive Sampling This innovative, non-invasive quantum microscopy technique opens the path to visualizing living organisms in their natural state without burning or damaging specimens with intense light energy. Furthermore, by actively exploiting quantum correlations and squeezed light states, it easily surpasses the diffraction limits and shot-noise limits of conventional microscopes, making it possible to observe the minute dynamics of intermolecular interactions. This study eloquently demonstrates that quantum imaging technology, which provides unprecedented ultra-high resolution without the risk of destructive sampling, is the core key that will fundamentally shift the paradigm of next-generation biology and precision medicine research. #QuantumImaging #BiologicalImaging #QuantumEntanglement #NonInvasiveImaging #QuantumMicroscopy #PhotonEntanglement #OvercomingNoiseLimits #QuantumBiology #Biophysics #KoreanQuantumBiologySociety https://pmc.ncbi.nlm.nih.gov/articles/PMC12339294/