ABSTRACT Quantum imaging leverages the intrinsic sharpness of quantum correlations between entangled photon pairs, offering the potential for high spatial resolution and enhanced signal‐to‐noise performance. However, practical quantum imaging systems often suffer from complex optical architectures and long acquisition times, limiting their applicability in dynamic scenarios. In this work, we propose quantum Gabor holography (QGH) and introduce array‐based coincidence counting with joint probability analysis to directly extract the spatial correlations of entangled photon pairs. The system selectively identifies true photon‐pair events while effectively suppressing uncorrelated background photons and detector noise. Experiments confirm that correlation‐based QGH preserves intrinsic quantum spatial information, improves noise robustness, and enables reliable amplitude and phase reconstruction even under ultra‐weak photon flux. The proposed method provides an efficient and physically grounded pathway toward lensless, low‐light, and high‐resolution quantum imaging.
ABSTRACT Quantum imaging leverages the intrinsic sharpness of quantum correlations between entangled photon pairs, offering the potential for high spatial resolution and enhanced signal‐to‐noise performance. However, practical quantum imaging systems often suffer from complex optical architectures and long acquisition times, limiting their applicability in dynamic scenarios. In this work, we propose quantum Gabor holography (QGH) and introduce array‐based coincidence counting with joint probability analysis to directly extract the spatial correlations of entangled photon pairs. The system selectively identifies true photon‐pair events while effectively suppressing uncorrelated background photons and detector noise. Experiments confirm that correlation‐based QGH preserves intrinsic quantum spatial information, improves noise robustness, and enables reliable amplitude and phase reconstruction even under ultra‐weak photon flux. The proposed method provides an efficient and physically grounded pathway toward lensless, low‐light, and high‐resolution quantum imaging.
Quantum holography exploits quantum correlation in entangled photon pairs to enhance holography. An inherent principle of holography is that each partial hologram can enhance the reconstruction of the entire object, a property that has not yet been explored in the quantum realm. The current fabrication technology for single-photon detectors is limited, making it extremely challenging to manufacture large-area detectors. Since resolution is directly related to the system aperture, achieving a resolution equivalent to that of a large-area detector under the constraint of a limited detection area is a key challenge for realizing high-resolution quantum holography. Here we demonstrate that the spatial correlations of entangled photons can extract crucial additional information from photon wave packets beyond the boundaries of the experimentally recorded region, where the photons have no direct interaction with the object. We validate the approach experimentally and benchmark it against the approach using only the detection area, achieving the advancements with an increase of up to 15 dB in signal-to-noise ratio and up to approximately tenfold improvement in structural similarity. We show the versatility of the approach by demonstrating significantly improved performance across various objects, including quantum holography of complex biological specimens. This work can advance the nascent field of quantum holography and accelerate its application in life sciences and biological systems.
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.
Classical light sources emit a randomly-timed stream of individual photons, the spatial distribution of which can be detected with a camera to form an image. Quantum light sources, based on parametric down conversion, emit photons as correlated photon-pairs. The spatial correlations between the photons enables imaging systems where the preferential selection of photon-pairs allows for enhancements in the noise performance over what is possible using classical light sources. However, until now the technical challenge of measuring, and correlating both photons has led to system complexity. Here we show that a camera capable of resolving the number of individual photons in each pixel of the detector array can be used to record an image formed from these photon-pair events and hence achieve a greater contrast than possible using a classical light source. We achieve an enhancement in the ratio of two-photon events compared to one-photon events using spatially correlated SPDC light compared to uncorrelated illumination by a LED. These results indicate the potential advantages of using photon counting cameras in quantum imaging schemes and these advantages will further increase as the technology is developed. Operating in photon sparse regimes such systems have potential applications in low-light microscopy and covert imaging.
This study investigates quantum holography, emphasizing its capability to conduct holographic imaging without the requirement for first-order coherence—a limitation of classical physics. By harnessing quantum entanglement, where image data is embedded in the phase correlation of polarization-entangled photon pairs and spread across the transverse spatial dimension, quantum holography enhances imaging performance. This technique not only improves resolution for polarization-sensitive phase objects but also provides resilience against stochastic phase fluctuations and uncontrolled ambient light, offering significant tangible benefits compared to conventional holography. Additionally, its integration with quantum tomography enables precise analysis of multi-dimensional hyper-entangled states, advancing quantum state analysis. Although current challenges remain, such as extended acquisition times due to technological constraints, ongoing advancements in faster, more affordable sensors are expected to address these issues. As a result, quantum holography is poised to have broad applications in biological imaging, sensing, and the exploration of complex high-dimensional quantum states. These developments position quantum holography as a crucial technology in the future of quantum optical communication and information processing, driving innovation and opening new avenues in these fields.
Quantum technology promises improvements in imaging, computing, and communication, for example using the resource of entanglement between photons with spatial correlations. Detecting spatial correlations, or coincidences, between entangled photons scalably, efficiently, and affordably is therefore an essential capability. However, this task is non-trivial for existing camera technologies, which require low illumination intensities or low detection duty cycles to count coincidences at high signal-to-noise ratios, resulting in long acquisition time, or use expensive custom electronic components. Here, we present an entanglement imaging system based around a novel Single-Photon Avalanche Diode (SPAD) array camera, optimized for sparse illumination with correlated photon pairs. The system is capable of maintaining a duty cycle close to 100%, while simultaneously detecting spatially resolved coincidences with high SNR, enabling the acquisition of real-time entanglement videos at a ~Hz frame rate. We use our system to demonstrate real-time monitoring of entanglement interference visibility, optical system point spread function, as well as real-time widefield entanglement-enhanced phase imaging. Our results show that SPAD array cameras represent a natural choice for scalable entanglement detection and imaging applications.
Abstract Quantum correlation of two‐photon states is utilized to suppress the environmental noise in imaging down to the single‐photon level. However, the size of the coherence area of the photon pairs limits the applications of quantum imaging based on spatial correlations. Here, a quantum imaging scheme exploiting twisted photon pairs with tunable spatial‐correlation regions to circumvent this limitation is proposed. A bulk‐density coincidence is employed to enhance the imaging signal. Specifically, a re‐scaled image signal is introduced, which is immune to the background intensity distribution profile of the photon pulse. A destructive interference between the anti‐bunched photon pair and bunched photon pair in the imaging process is revealed. This work can pave a way for twisted‐photon‐based quantum holography and quantum microscopy.