Quantum imaging is an emerging field that offers several advantages over classical protocols. Researchers have been exploring the use of undetected probing photons to achieve super-resolution imaging in low-photon flux scenarios. Additionally, quantum protocols based on interference and entanglement can be designed without classical counterparts. However, one of the challenges in quantum imaging is dealing with noise. In a recent study published in Science Advances, Jorge Fuenzalida and his team demonstrated a method that enables the generation of high-quality images of objects even in the presence of extreme noise levels. They introduced a quantum imaging distillation technique to detect single photons only. Let’s delve deeper into this ground-breaking research.
The method employed by Fuenzalida and his team is known as Quantum Imaging with Undetected Light (QIUL). It involves using photon pairs, where one photon illuminates the object and its partner photon is detected on the camera. The key idea is that the illuminating photon remains undetected. This approach allows for a unique discovery method to probe samples. To ensure the resilience of the method to noise, the team introduced a source of noise in the quantum imaging scheme and tested its performance even for noise intensities exceeding 250 times the quantum signal intensity.
One of the challenges in quantum imaging is cleaning the image from noise. Fuenzalida and his team proposed a distillation method called Quantum Holography with Undetected Light (QHUL) to remove unwanted noise signals superimposed over the quantum image on the camera. The principle behind this distillation method is to carry the object information into a single-photon interference pattern. If the intensity difference of the method is greater than the intensity variance of noise, the quantum image can be successfully distilled.
To generate photon pairs, the researchers used spontaneous parametric down-conversion, where an intense pump beam interacts with the atoms of a nonlinear crystal. The imaging setup involved an interferometer to generate a pair of signal-idler photons. The noise variance in the setup contributed to the signal intensity variance. The team implemented an experimental setup using a nonlinear interferometer in a Michelson configuration and pumped a crystal with a continuous wave laser. They carefully controlled the properties of classical illumination, such as intensity and variance, to examine the effects of noise and the distillation performance.
Through the QIUL method, Fuenzalida and colleagues were able to achieve two-photon wide-field interferometric imaging. While one photon illuminated the object, its partner photon remained on the camera, undetected. The image cleaning was performed using quantum holography with undetected light (QHUL). The team superimposed classical and quantum images to assess the distillation performance under various intensities of noise. Surprisingly, the method worked consistently, even when noise intensities exceeded the signal intensity.
To further explore the capabilities of the method, the team conducted simulations of quantum holography under extreme noise scenarios. The experimental outcomes of this study provide valuable insights into the potential of quantum imaging in open systems. It also paves the way for the development of innovative versions of quantum-based light detection and ranging (LIDAR) using undetected light.
The study by Fuenzalida and his team demonstrates the remarkable potential of quantum imaging techniques. By harnessing the properties of quantum interference and entanglement, they have achieved high-quality imaging even in the presence of extreme noise levels. The QIUL method, in combination with quantum holography, allows for the distillation of quantum images, eliminating unwanted noise signals. This research opens up exciting possibilities for quantum-based imaging technologies and paves the way for further advancements in the field.