Recently, a group of researchers from the University of Ottawa, the National Research Council of Canada, and Imperial College London published a study in which they developed a new method of recording holograms using quantum particles.
What is Holography?
While holograms are a frequent trope in the futuristic worlds of science fiction, the process for recording holograms was actually discovered over half a century ago in 1948. Unlike regular photography, which only captures the amplitude data of light, holography records both amplitude and phase data. Amplitude is a measure of the intensity or brightness of light. Therefore, traditional photography records images based on variations in the brightness of the light that reflects off of objects in the environment. However, because amplitude only gives information about light intensity, the images produced by traditional photography can only be rendered in two dimensions. In contrast, phase data gives information about how light interacts with objects. As such, holography is able to record three-dimensional information such as the depths and contours of objects.
How Holograms Are Recorded Using Traditional Technologies
In order to capture phase data, traditional holography techniques first require the emission of two coherent beams of light, with coherent referring to the fact that the two beams are of the same wavelength. These beams are traditionally created with lasers, which emit light at a constant wavelength. One beam is then aimed at the object being recorded. Light reflecting off the object is then collected by a holographic film. Simultaneously, the other beam is reflected off a mirror directly onto the film. Light from the two beams will then interact with each other as they meet, resulting in interference patterns on the film. When coherent light is then passed through the film, the interference pattern will bend and diffract the light to exactly reproduce the properties of the light that was recorded from the object. This process results in a three-dimensional projection of the recorded object.
Advantages of Quantum Holography
The main advantage of quantum holography is the fact that the recording process does not require two beams of coherent light. In the traditional technique, phase data is recorded in the form of interference patterns between the object beam and the reference beam. In contrast, quantum holography exploits the phenomenon of quantum entanglement to forego the requirement for coherence. Quantum entanglement is a phenomenon where pairs of quantum particles (e.g., photons of light) are intrinsically connected, with each particle mirroring the properties of the other regardless of the separation between them.
This unique property of quantum particles helps to mitigate many of the drawbacks of traditional holography. For example, because there is no need for coherence, the reference beam can be a different wavelength (i.e., colour) than the object beam. This advantage is critical for many medical applications because while infrared light is better for scanning biological tissues, it is much harder to accurately detect using current sensor technology. However, by taking advantage of quantum entanglement, biological tissues can be scanned using a beam of infrared light. A hologram of the specimen can then be created by recording the entangled partner beam, which may be in the visible spectrum and thus easier to measure.
Aside from being able to scan objects with a wider range of wavelengths of light, the researchers also noted that the stability of quantum entangled states allows for their technique to be more resistant to vibrations during the recording process. While traditional holography could only be achieved using very short exposure times, the technique developed by the researchers allows for recording over extended durations, resulting in holograms with superior fidelity and resolution.
Potential Future Applications
While the study was more of a proof-of-concept, the researchers are confident that their work will contribute towards the development of accurate 3D scene reconstruction, which may have a variety of applications ranging from self-driving vehicles to augmented reality.
