Quantum imaging utilizing entangled photon pairs takes advantage of their strong quantum correlations to surpass the limitations of classical imaging techniques in terms of spatial resolution and signal-to-noise ratio. However, due to the low brightness of entangled photon sources, an enormous amount number of intensity images (\(\sim 10^7\)) is required for imaging, posing a challenge for practical implementation. In this study, we propose the use of a BiBO crystal for generating entangled photons to enhance the efficiency of quantum imaging. A BiBO crystal has large nonlinear optical coefficient, so it has been expected to serve as a high-brightness entangled photon source. However, a BiBO crystal has never been applied to quantum imaging because it's relatively recently discovered. Here, we investigate the potential of a BiBO crystal as a light source for high-efficiency quantum imaging by performing parallel intensity correlation measurements and implementing quantum image distillation as an example in comparison with the commonly used a BBO crystal. As a result, we achieved a tenfold reduction in measurement time of the conventional method and a significant improvement in imaging efficiency.
Quantum imaging utilizing entangled photon pairs takes advantage of their strong quantum correlations to surpass the limitations of classical imaging techniques in terms of spatial resolution and signal-to-noise ratio. However, due to the low brightness of entangled photon sources, an enormous amount number of intensity images ((\sim 10^7)) is required for imaging, posing a challenge for practical implementation. In this study, we propose the use of a BiBO crystal for generating entangled photons to enhance the efficiency of quantum imaging. A BiBO crystal has large nonlinear optical coefficient, so it has been expected to serve as a high-brightness entangled photon source. However, a BiBO crystal has never been applied to quantum imaging because it's relatively recently discovered. Here, we investigate the potential of a BiBO crystal as a light source for high-efficiency quantum imaging by performing parallel intensity correlation measurements and implementing quantum image distillation as an example in comparison with the commonly used a BBO crystal. As a result, we achieved a tenfold reduction in measurement time of the conventional method and a significant improvement in imaging efficiency.
Quantum imaging utilizing entangled photon pairs takes advantage of their strong quantum correlations to surpass the limitations of classical imaging techniques in terms of spatial resolution and signal-to-noise ratio. However, due to the low brightness of entangled photon sources, an enormous number of intensity images (∼107) is required for imaging in previous studies in order to acquire images with a sufficient signal-to-noise ratio, posing a challenge for practical implementation. A BiBO crystal, known for its large nonlinear optical coefficient, is considered a promising high-brightness entangled photon source. However, its performance has not been quantitatively evaluated in the context of quantum imaging systems, particularly regarding its impact on imaging performance. Here, we investigate the potential of a BiBO crystal as a light source for high-efficiency quantum imaging by performing parallel intensity correlation measurements and implementing quantum image distillation as an example in comparison with a commonly used BBO crystal. The results demonstrate that the use of the BiBO crystal enables more efficient quantum imaging compared to the conventional BBO crystal.
Quantum imaging utilizes the correlation of photons to enhance the security, covertness, and noise resilience of optical imaging. Despite recent advances, developing a quantum imaging system with long-distance and strong noise resilience remains challenging. Here, we present an experimental demonstration of high-performance quantum imaging at telecom band with enhanced noise resilience. We use a fiber-integrated quantum light source via cascaded second-order nonlinear processes to generate high-quality correlated/entangled photon pairs at telecom band and a fiber-coupled confocal optical system to effectively suppress the background noise and improve the collection efficiency of echo signal photons by optimizing its bandwidth and aperture. In our demonstration, the quantum imaging with correlated/entangled photon pairs or heralded single photons is achieved at a distance of 11 m under indoor illumination. When the detected environment noise is 33 dB stronger than the signal photons, corresponding to a coincidence-to-accidental coincidence ratio of 1.7 ± 0.1, an imaging contrast of 0.23 ± 0.09 is achieved, which is 46 times higher than single-photon imaging without correlation. The results will open venues for the development of practical quantum imaging techniques.
We describe the full characterization of the biaxial nonlinear crystal BiB₃O₆ (BiBO) as a polarization entangled photon source using non-collinear type-II parametric down-conversion. We consider the relevant parameters for crystal design, such as cutting angles, polarization of the photons, effective nonlinearity, spatial and temporal walk-offs, crystal thickness and the effect of the pump laser bandwidth. Experimental results showing entanglement generation with high rates and a comparison to the well investigated β-BaB₂O₄ (BBO) crystal are presented as well. Changing the down-conversion crystal of a polarization entangled photon source from BBO to BiBO enhances the generation rate as if the pump power was increased by 2.5 times. Such an improvement is currently required for the generation of multiphoton entangled states.
Correlation imaging based on entangled light sources offers potential benefits over classical single-photon imaging (SPI) in noisy environments, but also faces challenges such as low brightness, long integration times, and difficulty imaging biological organisms. Here, we propose noise-resistant biologically correlated biphoton imaging (CPI) based on a super-bunching light source, addressing the challenge of severe signal-to-noise ratio degradation in conventional SPI schemes. Our CPI, based on a super-bunching light source with high brightness, broadband spectrum (400–1100 nm), and strong quantum correlation (g 2 (0) ∼ 250), delivers high-performance, noise-resistant operation by extracting correlated photon pairs between the reference and signal paths. Experimental results show that under extreme noise conditions (noise-to-signal ratio up to 600), the structural profile in conventional SPI is entirely obscured by noise. In contrast, CPI still clearly resolves the target structure. Quantitative analysis further reveals that, as noise intensity increases, the imaging visibility of CPI can be enhanced by more than two orders of magnitude compared to SPI schemes. This study confirms the exceptional robustness and practical utility of super-bunching light-based correlated imaging in high-noise environments, offering an effective technical approach for high-quality biological observation in complex optical conditions.
Quantum imaging is emerging as a transformative approach for biomedical applications, applying nonclassical properties of light, such as entanglement, squeezing, and quantum correlations, to overcome fundamental limits of conventional techniques. These methods promise superior spatial resolution, enhanced signal-to-noise ratios, improved phase sensitivity, and reduced radiation dose, for potentially safer and more precise imaging for delicate biological samples. Here, we present an overview of quantum optical biomedical imaging technologies as well as quantum-inspired imaging methods, including quantum optical coherence tomography, quantum optical microscopy, ghost imaging, multi-parameter quantum imaging, and imaging with quantum-grade cameras. We describe the operating principles, biomedical applications, and unique advantages of each approach, along with the specific challenges for their translation into real-life practice. This review aims to guide future research toward advancing quantum imaging from experimental demonstrations to impactful biomedical tools.
We use entangled photons as the light source in a normal microscope. Using this quantum illumination improves both the resolution and noise rejection in the image. The resolution of any classical imaging system is limited by the diffraction created by the finite size of the imaging lens. By using a light source that emits pairs of entangled photons and carefully controlling a camera that is capable of detecting single photons it is possible to observe these photons arriving two-by-two. Applying camera analysis software to log only these two-by-two events one can form an image from the mid-point (bisector) of each of these pair events. The image formed from the sum of all these bisectors has an improved resolution that surpasses the classical limit. Another advantage of using a quantum illumination is that it allows the two-by-two events from entangled photon pairs to be distinguished from background (classical) light and sensor noise. When processed in this way the resulting image is free of camera noise and any background light may be eliminated. The use of a quantum illumination protocol such as that used here results in the elimination of background light and therefore allows the development of the optical equivalent of quantum radar – a quantum enhanced LIDAR scheme. Using quantum illumination, combined with commercially available cameras that are sensitive to single photons creates a new approach to super-resolution and low noise microscopy. Imaging through noise with quantum illumination, T Gregory, P-A Moreau, E Toninelli, and M J Padgett, Science Advances 6, eaay2652 (2020) Resolution-enhanced quantum imaging by centroid estimation of biphotons, E Toninelli, P-A Moreau, T Gregory, A Mihalyi, M Edgar, N Radwell, and M J Padgett, Optica 6, 347-353 (2019)