Holography Enabled by Quantum Entanglement
A team of researchers reports in Nature physics on a technique based to extract the quantum information hidden in a signal that carries both classical and quantum information.
This technique opens a new pathway for quantum enhanced microscopes that use polarisation entanglement to encode phase information about a transparent object and uses low-intensity incoherent light for the observation of light sensitive samples.
The study has been selected to illustrate the cover of the magazine
Current super-resolution microscopes or microarray laser scanning technology are very sensitive devices with very good resolutions, but they implement high light power to study samples, light that ends up damaging or perturbing the sample when illuminated by these devices.
In these past years, quantum light has taken a prominent role in imaging techniques since its capabilities in terms of resolution and sensitivity can surpass classical limitations and, in addition, it does not damage the sample. This is possible because quantum light is emitted in single photons and uses the property of entanglement to reach lower light intensity regimes.
As for holography, this technique can be applied from the X-rays to the radios and is an essential tool for microscopic imaging, data storage, optical security, among others. Holography implements a feature of light, called coherence, which is based on extracting classical information about the phase of light through interference patterns. By classical coherence, we refer to that fact that the beams of photons have all the same frequency and move all in synchronization.
If there is no coherence, there is no interference, and it is impossible to maintain a stable holographic image, thus no useful information can be retrieved. Even more so, mechanical instabilities, random phase disorder or even stray light can degrade the coherence level of the light being employed, and thus hamper the quality of images obtained in the process.
Thus, in a study recently published in Nature Physics, researchers Hugo Defienne, Bienvenu Ndagano, Ashley Lions, led by Prof. Daniele Faccio from the University of Glasgow and partners of the European Q-MIC project, report on an approach in which they are capable of obtaining a holographic imaging technique that is much better than classical holography and which is based on quantum entanglement, the feature responsible of carrying the image information.
In their study and experimental setup, the researchers have introduced a holographic imaging approach that does not use the classical first-order coherence of the light to extract the image information. Instead, the approach relies on the second-order coherence of the entangled quantum states of light, which uses the polarization feature of entangled photons pairs to extract the phase information of complex object images. Such technique has proven to achieve a spatial resolution enhancement that is a factor of 1.84 higher when compared to the classical holographic techniques used so far.
By using the features of quantum entanglement, the technique has proven that quantum holography based on spatial-polarized hyper-entangled photons to image objects, can be so robust that it not only is unsensitive to phase disorder scenarios, which is a major problem for classical holography, but also shows to be robust against the presence of strong classical noise or background light from classical sources.
This technique opens a new pathway for several applications. It proves a useful technique for quantum communications and information processing techniques, since quantum holography can be used to characterize entanglement in both space and polarization across many, e.g. 100.000 modes. In addition, with the rapid advancement of quantum correlation techniques, this approach can definitely be useful for quantum imaging, in particular for quantum enhanced microscopes, for biological imaging and sensing of ultra-sensitive samples, the main goal of the Q-MIC.
Description: Space-polarization hyper-entangled photon pairs propagate through two SLMs (Alice SLM and Bob SLM) and are detected by two EMCCD cameras (Alice EMCCD and Bob EMCCD)
Description: images of the smiley face showing the imaging technique have been selected to grace the cover of Nature Physics
Reference: Polarization entanglement-enabled quantum holography, Hugo Defienne, Bienvenu Ndagano, Ashley Lyons & Daniele Faccio, Nature Physics volume 17, pages591–597 (2021)
