Innovative quantum-inspired imaging technology excels in low-light conditions, opening new possibilities for medical imaging and art preservation.
Researchers from the Department of Physics at the University of Warsaw, together with colleagues from Stanford University and Oklahoma State University, have introduced a quantum-inspired phase imaging method based on optical intensity correlation measurements that is robust to phase noise. The new imaging method can operate in very low light and is proving useful in new applications such as infrared and X-ray interferometry imaging, quantum wave and matter wave interferometry.
Revolutionary imaging technology
Whether it’s taking a picture of a cat with your smartphone or imaging a cell culture with a state-of-the-art microscope, it’s done by measuring the intensity (brightness) of light pixel by pixel. Light is characterized not only by its intensity but also by its phase. Interestingly, transparent objects become visible if we can measure the phase delay of the light they introduce.
Phase-contrast microscopy, for which Fritz Zernike received the Nobel Prize in 1953, revolutionized biomedical imaging with the possibility of obtaining high-resolution images of a variety of transparent and optically thin samples. Research areas that have emerged from Zernike’s discoveries include modern imaging techniques such as digital holography and quantitative phase imaging.
Dr. Radek Lapkiewicz, head of the Quantum Imaging Laboratory at the Faculty of Physics at the University of Warsaw, said: “This will enable label-free quantitative characterization of biological specimens such as cell cultures, with potential applications in neurobiology and cancer research.” It has a certain gender,” he explains.
Challenges and innovations in phase imaging
However, there is still room for improvement. “For example, interferometry, which is the standard measurement method for determining precise thickness at any point on an object to be inspected, only works if the system is stable and not subjected to shocks or disturbances. For example, it is very difficult to carry out such tests in a moving car or on a shaking table,” explains Jerzy Šniewcz, PhD student at the Department of Physics at the University of Warsaw.
Researchers from the Department of Physics at the University of Warsaw, together with colleagues from Stanford University and Oklahoma State University, decided to tackle this problem and develop a new phase imaging method that is not affected by phase instability. Their research results were published in prestigious journals. scientific progress.
back to old school
How did researchers come up with the idea of a new technique? Already in the 60s, Leonard Mandel and his group discovered that even if the strength of interference is undetectable, correlation reveals its presence. We have proven that it is possible.
“Inspired by Mandel’s classic experiment, we wanted to investigate how intensity correlation measurements can be used for phase imaging,” explains Dr. Lapkiewicz. Correlation measurements look at pairs of pixels and observe whether they become brighter or darker at the same time.
“We have shown that such measurements contain additional information that cannot be obtained from a single photo, i.e., an intensity measurement. We exploit this fact to show that interference-based phase microscopy , demonstrated that observations are possible even when standard interferograms lose all phase information on average and no streaks are recorded in the intensity.
“Standard approaches would suggest that there is no useful information in such images. However, the information is hidden in correlations and can be recovered by analyzing multiple independent photos of the object. “This allows us to obtain perfect interferograms, even though normal interference cannot be detected due to noise,” Lapkiewicz added.
“In our experiments, we superimpose a reference beam on the light passing through the phase object (the object of investigation). A random phase delay is introduced between the object and reference light beams. This phase delay is Simulate disturbances that interfere with conventional phase imaging methods.
“As a result, no interference is observed when measuring the intensity, i.e. no information about the phase object is obtained from the intensity measurement. However, the correlation between the spatially dependent intensities is a fringe pattern that contains complete information about the phase object. It is displayed.
“This intensity-to-intensity correlation is not affected by temporal phase noise that varies slower than the speed of the detector (about 10 nanoseconds in the experiments performed), and is not affected by collecting data over arbitrarily long periods of time. This is a game changer because we can measure ” – longer measurements mean more photons, which translate into higher values Accuracy”, explains Jerzy Šniewicz, the first author of this work.
Simply put, even if you record one frame of film, that one frame does not provide useful information about what the object you are studying looks like. “So we first used a camera to record the entire series of frames, and then multiplied the measurements of each pair of points in each frame. We averaged these correlations and We recorded the statue,” explains Jerzy Šněvić.
“Different methods are possible to recover the phase profile of an observed object from a series of images. However, our method, based on correlation between intensities and a so-called off-axis holography technique, provides the best reconstruction accuracy. “We have shown that it does,” said Stanisław Krzyarek, second author of the paper.
Great idea for dark environments
Phase imaging techniques based on intensity correlation can be widely used in highly noisy environments. The new method works with both classical light (lasers and heat) and quantum light. It can also be implemented with photon For example, counting schemes using single-photon avalanche diodes. “It can be used when there is little light available or when high light intensities cannot be used to avoid damaging the object (for example, a delicate biological sample or a work of art),” explains Jerzy Szuniewicz. Masu.
“Our technique will expand the possibilities of phase measurements, including new applications such as infrared and X-ray imaging, quantum and matter wave interferometry,” concludes Dr. Lapkiewicz.
Reference: “Noise-tolerant phase imaging with intensity correlation” Jerzy Szuniewicz, Stanislaw Kurdzialek, Sanjukta Kundu, Wojciech Zwolinski, Radoslaw Chrapkiewicz, Mayuk Lahiri, Radek Lapkiewicz, September 22, 2023. scientific progress.
DOI: 10.1126/sciadv.adh5396
This research was carried out under the FIRST TEAM project “Spatio-temporal photon correlation measurements for quantum metrology and super-resolution microscopy” co-financed by the European Union under the European Regional Development Fund (POIR.04.04.00-00). was supported by the Polish Science Foundation. -3004/17-00). Jerzy Szuniewicz also acknowledges the support from the Polish National Science Center (grant number 2022/45/N/ST2/04249). S. Kurdzialek thanks the support from the National Science Center (Poland) grant No.2020/37/B/ST2/02134. M. Ahiri. acknowledges support from the U.S. Office of Naval Research (award number N00014-23-1-2778).