3 days ago
No camera? No problem: US engineers bend quantum rules to create 3D holograms
Holographic imaging just got a quantum at Brown University, including two undergraduate students, have developed a groundbreaking imaging technique that uses quantum entanglement to produce detailed 3D holograms without relying on traditional infrared cameras.
By pairing invisible infrared light to illuminate microscopic objects with visible light entangled at the quantum level, the novel technique captures not just intensity, but also the phase of light waves—an essential ingredient for true holographic imaging.
The result is sharp, depth-rich 3D images created using light that never actually touched the object.
'It sounds impossible, but they did it,' said Professor Jimmy Xu, a professor in Brown's School of Engineering and one of the supervising researchers, in a press release.
Dubbed Quantum Multi-Wavelength Holography, the technique overcomes longstanding challenges like phase wrapping, using dual entangled wavelengths to dramatically expand depth range.
'The technique allows us to gather better and more accurate information on the thickness of the object, which enables us to create accurate 3D images using indirect photons,' said Moe (Yameng) Zhang, a junior concentrating in engineering physics at Brown who co-led the work with fellow undergraduate Wenyu Liu.
Zhang and Liu presented their work earlier this month at the Conference on Lasers and Electro-Optics. Along with Xu, the work was supervised by Petr Moroshkin, a senior research associate.
'You could call this infrared imaging without an infrared camera,' Xu said. 'It sounds impossible, but they did it. And they did it in a way that enables great depth resolution in the images it produces.'
Traditional imaging methods, like X-rays or regular photographs, work by capturing light that bounces off an object. Quantum imaging, on the other hand, relies on the strange but powerful phenomenon of quantum entanglement—what Einstein once called 'spooky action at a distance.'
When two photons are entangled, a change in one instantly affects the other, no matter how far apart they are.
In this technique, one photon—called the 'idler'—interacts with the object, while its entangled partner—the 'signal' photon—is used to actually form the image.
In the Brown team's new approach, they used a special crystal to generate pairs of photons: infrared photons to scan the object and visible-light photons to create the image. This setup offers a big advantage: Infrared light is ideal for probing delicate or hidden structures, while visible light allows imaging using standard, affordable detectors.
'Infrared wavelengths are preferred for biological imaging because they can penetrate skin and are safe for delicate structures, but they require expensive infrared detectors for imaging,' said Liu.
'The advantage of our approach is that we can use infrared for probing an object, but the light we use for detection is in visible range. So we can use standard, inexpensive silicon detectors.'
The major breakthrough in this work is bringing quantum imaging into the 3D world by solving a common problem called 'phase wrapping.' This issue comes up in imaging methods that rely on the phase of light waves—their peaks and valleys—to measure the depth of an object. When the features on an object are deeper than the light's wavelength, the wave pattern can repeat, making it hard to tell apart shallow features from deeper ones.
To navigate this, the Brown team used two sets of entangled photons with slightly different wavelengths. This small difference creates a much longer 'synthetic' wavelength, allowing the system to accurately measure much deeper contours and produce more reliable 3D images.
'By using two slightly different wavelengths, we effectively create a much longer synthetic wavelength — about 25 times longer than the originals,' Liu said. 'That gives us a much larger measurable range that's more applicable to cells and other biological materials.'
The team successfully created a holographic 3D image of a tiny metal letter 'B' about 1.5 millimeters wide to demonstrate the technique in a nod to Brown University. They say it's a strong proof-of-concept that shows the potential of quantum entanglement for generating high-quality 3D images. Both Liu and Zhang said they were excited to share their work at an international scientific conference.
'We had been reading papers by pioneers in this field, so it was great to be able to attend the conference and meet some of them in person,' Zhang said. 'It's really an amazing opportunity.'
The research was funded by the Department of Defense and the National Science Foundation.
