Quantum holography

Rajesh Uppal May 17, 2021 Photonics, Quantum Comments Off on Quantum holography 1,122 Views

We see things because our eyes are sophisticated light detectors: they constantly capture the light rays bouncing off nearby objects so our brain can construct an ever-changing impression of the world around us. Photography, as this became known, has revolutionized the way people see and engage with the world but no matter how realistic or artistic a photograph appears, there’s no question of it being real. We look at a photo and instantly see that the image is dead history: the light that captured the objects in a photograph vanished long ago and can never be recaptured. Holograms are a bit like photographs that never die. If you look at well-made holograms from different angles, you see objects from different perspectives just as you would a real object, even appearing to move as you walk past them.

Photography measures how much light of different color hits the photographic film. However, light is also a wave, and is therefore characterized by the phase. Phase specifies the position of a point within the wave cycle and correlates to depth of information, meaning that recording the phase of light scattered by an object can retrieve its full 3D shape, which cannot be obtained with a simple photograph. This is the basis of optical holography, popularized by fancy holograms in sci-fi movies like Star Wars.

A hologram is a recording in a two- or three-dimensional medium of the interference pattern formed when a point source of light (the reference beam) of fixed wavelength encounters light of the same fixed wavelength arriving from an object (the object beam). When the hologram is illuminated by the reference beam alone, the diffraction pattern recreates the wave fronts of light from the original object. Thus, the viewer sees an image indistinguishable from the original object.

With the invention of intense coherent light sources (lasers) and their most recent technological advancements, optical holography has become a popular technique for three-dimensional (3D) imaging of macroscopic objects, security applications, and microscopic imaging.

Holography also has military applications. Holograms and similar technologies offer the possibility of realistic, cost-effective training and education for a broad array of military missions and commercial applications. The military’s increased reliance on virtual reality to train warfighters may be converging with rapid advances in technology that will bring the holodeck of Star Trek fame closer to actuality. The U.S. military already has put virtual humans to good use. For example, the Institute for Creative Technologies (ICT) at the University of Southern California, Los Angeles, has used virtual reality characters to touch warfighters in one way or another before, during and after combat deployments

Dr. John Parmentola, Director of Research and Laboratory Management with the Army’s science and technology office is “making science fiction into reality” by creating realistic holographic images, generating virtual humans. They’re working on creating “photorealistic looking and acting human beings” that can think on their own, have emotions and talk in local slang. “I actually interact with virtual humans in terms of asking them questions and they’re responding,” Parmentola said.

The extraordinary promise of quantum technology—depend on quantum “entanglement,” in which the physical states of two or more objects such as atoms, photons or ions become so inextricably connected that the state of one particle can instantly influence the state of the other—no matter how far apart they are. Entanglement links the strange states of tiny quantum mechanical objects. For example, a top can spin either clockwise or counterclockwise, but an atom can spin both ways at once—at least until it is measured and that two-way state collapses one way or the other. Two atoms can be entangled so that each is in an uncertain two-way state, but their spins are definitely correlated, say, in opposite directions. So if physicists measure the first atom and find it spinning clockwise, they know instantly the other one must be spinning counterclockwise, no matter how far away it is.

Quantum holography makes use of entangled-photon pairs, one of which one scatters from the remote object while the other is locally manipulated using conventional optics that offers full spatial resolution. Remarkably, the underlying entanglement permits the measurement to yield coherent holographic information about the remote object. Quantum entanglement enables information processing with capabilities beyond technology based on classical principles

In 2016, Researchers Created a Quantum Hologram of Single photon

Until quite recently, creating a hologram of a single photon was believed to be impossible due to fundamental laws of physics. However, scientists at the Faculty of Physics, University of Warsaw, have successfully applied concepts of classical holography to the world of quantum phenomena. A new measurement technique has enabled them to register the first ever hologram of a single light particle, thereby shedding new light on the foundations of quantum mechanics.

However, in 2016 scientists successfully applied concepts of classical holography to the world of quantum phenomena. A new measurement technique has enabled them to register the first ever hologram of a single light particle, thereby shedding new light on the foundations of quantum mechanics. Scientists at the Faculty of Physics, University of Warsaw, created the first ever hologram of a single light particle. The spectacular experiment, reported in the journal Nature Photonics, was conducted by Dr. Radoslaw Chrapkiewicz and Michal Jachura under the supervision of Dr. Wojciech Wasilewski and Prof. Konrad Banaszek.

Their successful registering of the hologram of a single photon heralds a new era in holography: quantum holography, which promises to offer a whole new perspective on quantum phenomena. “We performed a relatively simple experiment to measure and view something incredibly difficult to observe: the shape of wavefronts of a single photon,” says Dr. Chrapkiewicz.

In standard photography, individual points of an image register light intensity only. In classical holography, the interference phenomenon also registers the phase of the light waves (it is the phase which carries information about the depth of the image). When a hologram is created, a well-described, undisturbed light wave (reference wave) is superimposed with another wave of the same wavelength but reflected from a three-dimensional object (the peaks and troughs of the two waves are shifted to varying degrees at different points of the image). This results in interference and the phase differences between the two waves create a complex pattern of lines. Such a hologram is then illuminated with a beam of reference light to recreate the spatial structure of wavefronts of the light reflected from the object, and as such its 3D shape.

One might think that a similar mechanism would be observed when the number of photons creating the two waves were reduced to a minimum, that is to a single reference photon and a single photon reflected by the object. And yet you’d be wrong! The phase of individual photons continues to fluctuate, which makes classical interference with other photons impossible. Since the Warsaw physicists were facing a seemingly impossible task, they attempted to tackle the issue differently: rather than using classical interference of electromagnetic waves, they tried to register quantum interference in which the wave functions of photons interact.

Wave function is a fundamental concept in quantum mechanics and the core of its most important equation: the Schrödinger equation. In the hands of a skilled physicist, the function could be compared to putty in the hands of a sculptor: when expertly shaped, it can be used to ‘mould’ a model of a quantum particle system. Physicists are always trying to learn about the wave function of a particle in a given system, since the square of its modulus represents the distribution of the probability of finding the particle in a particular state, which is highly useful. “All this may sound rather complicated, but in practice our experiment is simple at its core: instead of looking at changing light intensity, we look at the changing probability of registering pairs of photons after the quantum interference,” explains doctoral student Jachura.

Why pairs of photons? A year ago, Chrapkiewicz and Jachura used an innovative camera built at the University of Warsaw to film the behaviour of pairs of distinguishable and non-distinguishable photons entering a beam splitter. When the photons are distinguishable, their behaviour at the beam splitter is random: one or both photons can be transmitted or reflected. Non-distinguishable photons exhibit quantum interference, which alters their behaviour: they join into pairs and are always transmitted or reflected together. This is known as two-photon interference or the Hong-Ou-Mandel effect.

“Following this experiment, we were inspired to ask whether two-photon quantum interference could be used similarly to classical interference in holography in order to use known-state photons to gain further information about unknown-state photons. Our analysis led us to a surprising conclusion: it turned out that when two photons exhibit quantum interference, the course of this interference depends on the shape of their wavefronts,” says Dr. Chrapkiewicz.

Quantum interference can be observed by registering pairs of photons. The experiment needs to be repeated several times, always with two photons with identical properties. To meet these conditions, each experiment started with a pair of photons with flat wavefronts and perpendicular polarisations; this means that the electrical field of each photon vibrated in a single plane only, and these planes were perpendicular for the two photons. The different polarisation made it possible to separate the photons in a crystal and make one of them ‘unknown’ by curving their wavefronts using a cylindrical lens. Once the photons were reflected by mirrors, they were directed towards the beam splitter (a calcite crystal). The splitter didn’t change the direction of vertically-polarised photons, but it did diverge diplace horizontally-polarised photons. In order to make each direction equally probable and to make sure the crystal acted as a beam splitter, the planes of photon polarisation were bent by 45 degrees before the photons entered the splitter. The photons were registered using the state-of-the-art camera designed for the previous experiments. By repeating the measurements several times, the researchers obtained an interference image corresponding to the hologram of the unknown photon viewed from a single point in space. The image was used to fully reconstruct the amplitude and phase of the wave function of the unknown photon.

The experiment conducted by the Warsaw physicists is a major step towards improving our understanding of the fundamental principles of quantum mechanics. Until now, there has not been a simple experimental method of gaining information about the phase of a photon’s wave function. Although quantum mechanics has many applications, and it has been verified many times with a great degree of accuracy over the last century, we are still unable to explain what wave functions actually are: are they simply a handy mathematical tool, or are they something real?

“Our experiment is one of the first allowing us to directly observe one of the fundamental parameters of photon’s wave function — its phase — bringing us a step closer to understanding what the wave function really is,” explains Jachura.

The Warsaw physicists used quantum holography to reconstruct wave function of an individual photon. Researchers hope that in the future they will be able to use a similar method to recreate wave functions of more complex quantum objects, such as certain atoms. Will quantum holography find applications beyond the lab to a similar extent as classical holography, which is routinely used in security (holograms are difficult to counterfeit), entertainment, transport (in scanners measuring the dimensions of cargo), microscopic imaging and optical data storing and processing technologies? “It’s difficult to answer this question today. All of us — I mean physicists — must first get our heads around this new tool. It’s likely that real applications of quantum holography won’t appear for a few decades yet, but if there’s one thing we can be sure of it’s that they will be surprising,” summarises Prof. Banaszek.

New holographic technique developed in 2019 opens the way for quantum computation

The problem with photo/hologram is that it’s spatial resolution is limited by the wavelength of light, around or just-below 1 μm (0.001 mm). That’s fine for macroscopic objects, but it starts to fail when entering the realm of nanotechnology.

In 2019, the researchers from Fabrizio Carbone’s lab at EPFL have developed a method to see how light behaves on tiniest scale, well beyond wavelength limitations. The researchers used the most unusual photographic media: freely propagating electrons. Used in their ultrafast electron microscope, the method can encode quantum information in a holographic light pattern trapped in a nanostructure, and is based on an exotic aspect of electron and light interaction. The scientists used the quantum nature of the electron-light interaction to separate the electron-reference and electron-imaging beams in energy instead of space. This makes it now possible to use light pulses to encrypt information on the electron wave function, which can be mapped with ultra-fast transmission electron microscopy.

The new method can provide us with two important benefits: First, information on light itself, making it a powerful tool for imaging electromagnetic fields with attosecond and nanometer precision in time and space. Second, the method can be used in quantum computing applications to manipulate the quantum properties of free electrons.

“Conventional holography can extract 3D information by measuring the difference in distance that light travels from different parts of the object,” says Carbone. “But this needs an additional reference beam from a different direction to measure the interference between the two. The concept is the same with electrons, but we can now get higher spatial resolution due to their much shorter wavelength. For example, we were able to record holographic movies of quickly moving objects by using ultrashort electron pulses to form the holograms.”

Beyond quantum computations, the technique has the highest spatial resolution compared to alternatives, and could shift the way we think about light in everyday life. “So far, science and technology have been limited to freely propagating photons, used in macroscopic optical devices,” says Carbone. “Our new technique allows us to see what happens with light at the nanoscale, the first step for miniaturization and integration of light devices onto integrated circuits.”

WIMI Holographic Academy expects Quantum technology to be integrated into Hologram technology

Tailor Insight, the fintech market research organization, recently released a research report “WIMI Holographic Academy expects Quantum technology to be integrated into Hologram technology”. At present, the research and application prospects of quantum technology are becoming the focus of the development of frontier technology in China. The development of quantum technology has great scientific significance and strategic value. It is a major disruptive technological innovation that has an impact on the traditional technological system and makes breakthroughs. It will lead to a new round of technological revolution and industrial transformation.

In traditional holography, the film can use a non-scattered reference beam to record the interference pattern of monochromatic light scattered from the object being imaged. Scientists can then use the reference beam replica to illuminate the generated image, creating a virtual image of the original object. Holography was first proposed by physicist Dennis Garber in 1948. The purpose was to improve the resolution of electron microscopes and demonstrate them by optics. The hologram can be formed by superimposing the phase and amplitude distribution of the signal with a known reference. The original concept was electronic holography. After the invention of laser optical holography, it became a popular three-dimensional imaging macroscopic object, information encryption, and microscopic imaging technology.

However, the expansion of holograms into the ultrafast field remains a challenge in the field of electronics, although the development of this technology will provide the highest possible spatial and temporal resolution for advanced imaging applications in condensed matter physics. In the study, published in the Journal, Science Advances, Ivan Madan and an interdisciplinary research team at the departments of the ultra-fast microscope and electron scattering, physics, science, and technology in Switzerland, the UK, and Spain, describe in detail the process of making holograms by using local electromagnetic fields. Scientists used the ultra-fast transmission electron microscope (UEM) to obtain electromagnetic holograms with attosecond/nanometer resolution. In the new method, scientists rely on electromagnetic fields to split electron wave functions in quantum coherent superpositions of different energy states.

The researchers said that the latest experiments are important to understand the fundamental laws of quantum mechanics and help to better understand the nature of wave functions. They hope to use this method to create holograms of more complex quantum objects. Recently, WIMI has established the “Holographic Academy of Science” to conduct research on the cutting-edge technology of holographic AR and technology innovation. WIMI Holographic Academy is committed to the unknown of holographic vision technology, with the driving force of regarding human vision as the goal, to carry out basic science and innovative technology research. It aims to promote cutting-edge research in computer science and related fields, such as holography and quantum computing, facing the actual industry scenarios and the future world. It will establish a platform for industry-research cooperation, promote the application of major scientific and technological innovations, and build a deeply integrated ecosystem of industries and research centers.

At present, the Holographic Academy has developed rapidly. In just one month, it has mobilized many scientists around the world to participate in the “new technology strategy”. The Holographic Academy will also set up a strong research and development system for the field of holographic vision to serve the global new economy to reserve core technologies. WIMI Holographic Academy focuses more on in-depth exploration in professional and vertical fields, and expands scientific research on the future world in the following areas:

1. Holographic computing science: biological holographic computing, quantum holographic computing, photon holographic computing, neutrino holographic computing, and maglev holographic computing.

2. Holographic communication science: quantum holographic communication, dark matter holographic communication, vacuum holographic communication, photon holographic communication, quark holographic communication, maglev holographic communication, and brain-machine holographic communication.

3. Micro-integration science: neutrino micro-integration, biological micro-integration, photonic micro-integration, quantum micro-integration, maglev micro-integration, decay micro-integration, fusion micro-integration, and fission micro-integration.

4. Holographic cloud science: quantum holographic cloud, photon holographic cloud, atmospheric holographic cloud, and space holographic cloud.

The establishment of WIMI Holographic Academy of Sciences is conducive to the use of advanced artificial intelligence vision research and talent reserve resources to further improve the global research and development layout of WIMI, and seize more opportunities for development through advanced technologies in the coming 5G era.