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Category: quantum physics – Page 596

Scientists create smallest semiconductor laser that works in visible range at room temperature.

An international team of researchers led by researchers from ITMO University announced the development of the world’s most compact semiconductor laser that works in the visible range at room temperature. According to the authors of the research, the laser is a nanoparticle of only 310 nanometers in size (which is 3,000 times less than a millimeter) that can produce green coherent light at room temperature. The research article was published in ACS Nano.

This year, the international community of optical physicists celebrates the anniversary of a milestone event: 60 years ago, in the middle of May, American physicist Theodor Maiman demonstrated the operation of the first optical quantum generator — a laser. Now, Sixty years later, an international team of scientists published a work where they demonstrated experimentally the world’s most compact semiconductor laser that operates in the visible range at room temperature. This means that the coherent green light that it produces can be easily registered and even seen by a naked eye using a standard optical microscope.

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Physicists have measured the flight times of electrons emitted from a specific atom in a molecule upon excitation with laser light. This has enabled them to measure the influence of the molecule itself on the kinetics of emission.

Photoemission — the release of electrons in response to excitation by light — is one of the most fundamental processes in the microcosm. The kinetic energy of the emitted electron is characteristic for the atom concerned, and depends on the wavelength of the light employed. But how long does the process take? And does it always take the same amount of time, irrespective of whether the electron is emitted from an individual atom or from an atom that is part of a molecule? An international team of researchers led by laser physicists in the Laboratory for Attosecond Physics (LAP) at LMU Munich and the Max Planck Institute of Quantum Optics (MPQ) in Garching has now probed the influence of the molecule on photoemission time.

The theoretical description of photoemission in 1905 by Albert Einstein marked a breakthrough in quantum physics, and the details of the process are of continuing interest in the world of science and beyond. How the motions of an elementary quantum particle such as the electron are affected within a molecular environment has a significant bearing on our understanding of the process of photoemission and the forces that hold molecules together.

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Researchers from the Moscow Institute of Physics and Technology, joined by a colleague from Argonne National Laboratory, U.S., have implemented an advanced quantum algorithm for measuring physical quantities using simple optical tools. Published in Scientific Reports, their study takes us a step closer to affordable linear optics-based sensors with high performance characteristics. Such tools are sought after in diverse research fields, from astronomy to biology.

Maximizing the sensitivity of measurement tools is crucial for any field of science and technology. Astronomers seek to detect remote cosmic phenomena, biologists need to discern exceedingly tiny organic structures, and engineers have to measure the positions and velocities of objects, to name a few examples.

Until recently, no measurement could ensure precision above the so-called shot noise limit, which has to do with the statistical features inherent in classical observations. Quantum technology has provided a way around this, boosting precision to the fundamental Heisenberg limit, stemming from the basic principles of quantum mechanics. The LIGO experiment, which detected for the first time in 2016, shows it is possible to achieve Heisenberg-limited sensitivity by combining complex optical interference schemes and quantum techniques.

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In the consumer electronics industry, quantum dots are used to dramatically improve color reproduction in TV displays. That’s because LCD TV displays, the kind in most of our living rooms, require a backlight. This light is typically made up of white, or white-ish LEDs. The LCD filters the white light into red, green, and blue pixels; their combinations create the colors that appear on the screen.

Before quantum dots, filtering meant that much of the light didn’t make it to the screen. Putting a layer of quantum dots between the LEDs and the LCD, however, changes that equation. QD TVs use blue LEDs as the light source, then take advantage of the quantum effect to shift some of that light to tightly constrained red and green wavelengths. Because only this purified light reaches the filters—instead of the full spectrum that makes up white light—far less is blocked and wasted.

It turns out that this same approach to making your TV picture better can make plants grow faster, because plants, like LCD filters, are tuned to certain colors of light.

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It’s always exciting when you can bridge two different physical concepts that seem to have nothing in common—and it’s even more thrilling when the results have as broad a range of possible fields of application as from fault-tolerant quantum computation to quantum gravity.

Physicists love to draw connections between distinct ideas, interconnecting concepts and theories to uncover new structure in the landscape of scientific knowledge. Put together information theory with quantum mechanics and you’ve opened a whole new field of quantum information theory. More recently, machine learning tools have been combined with many-body physics to find new ways to identify phases of matter, and ideas from quantum computing were applied to Pozner molecules to obtain new plausible models of how the brain might work.

In a recent contribution, my collaborators and I took a shot at combining the two physical concepts of quantum error correction and physical symmetries. What can we say about a quantum error-correcting code that conforms to a physical symmetry? Surprisingly, a continuous symmetry prevents the code from doing its job: A code can conform well to the symmetry, or it can correct against errors accurately, but it cannot do both simultaneously.

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According to new research by SISSA, ICTP and INFN, black holes could be like holograms, in which all the information to produce a three-dimensional image is encoded in a two-dimensional surface. As affirmed by quantum theories, black holes could be incredibly complex, and concentrate an enormous amount of information in two dimensions, like the largest hard disks that exist in nature. This idea aligns with Einstein’s theory of relativity, which describes black holes as three dimensional, simple, spherical and smooth, as depicted in the first-ever image of a black hole that circulated in 2019. In short, black holes appear to be three dimensional, just like holograms. The study, which unites two discordant theories, has recently been published in Physical Review X.

The mystery of black holes

For scientists, pose formidable theoretical challenges for many reasons. They are, for example, excellent representatives of the great difficulties of theoretical physics in uniting the principles of Einstein’s general theory of relativity with those of the quantum physics of . According to the relativity, black holes are simple bodies without information. According to , as claimed by Jacob Bekenstein and Stephen Hawking, they are the most complex existing systems because they are characterized by enormous entropy, which measures the complexity of a system, and consequently contain a lot of information.

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Technion Professor Ido Kaminer and his team have made a dramatic breakthrough in the field of quantum science: a quantum microscope that records the flow of light, enabling the direct observation of light trapped inside a photonic crystal.

Their research, “Coherent Interaction Between Free Electrons and a Photonic Cavity,” was published in Nature. All the experiments were performed using a unique ultrafast transmission electron microscope at the Technion-Israel Institute of Technology. The microscope is the latest and most versatile of a handful that exist in the scientific world.

“We have developed an electron microscope that produces, what is in many respects, the best near- field optical microscopy in the world. Using our microscope, we can change the color and angle of light that illuminates any sample of nano materials and map their interactions with electrons, as we demonstrated with photonic crystals,” explained Prof. Kaminer. “This is the first time we can actually see the dynamics of light while it is trapped in nano materials, rather than relying on ,” added Dr. Kangpeng Wang, a postdoc in the group and first author on the paper.

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