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Optica l quantum technologies are based on the interactions of atoms and photons at the single-particle level, and so require sources of single photons that are highly indistinguishable – that is, as identical as possible. Current single-photon sources using semiconductor quantum dots inserted into photonic structures produce photons that are ultrabright but have limited indistinguishability due to charge noise, which results in a fluctuating electric field. Conversely, parametric down conversion sources yield photons that while being highly indistinguishable have very low brightness. Recently, however, scientists at CNRS — Université Paris-Saclay, Marcoussis, France; Université Paris Diderot, Paris, France; University of Queensland, Brisbane, Australia; and Université Grenoble Alpes, CNRS, Institut Néel, Grenoble, France; have developed devices made of quantum dots in electrically-controlled cavities that provide large numbers of highly indistinguishable photons with strongly reduced charge noise that are 20 times brighter than any source of equal quality. The researchers state that by demonstrating efficient generation of a pure single photon with near-unity indistinguishability, their novel approach promises significant advances in optical quantum technology complexity and scalability.

Dr. Pascale Senellart and Phys.org discussed the paper, Near-optimal single-photon sources in the solid state, that she and her colleagues published in Nature Photonics, which reports the design and fabrication of the first optoelectronic devices made of quantum dots in electrically controlled cavities that provide bright source generating near-unity indistinguishability and pure single photons. “The ideal single photon source is a device that produces light pulses, each of them containing exactly one, and no more than one, photon. Moreover, all the photons should be identical in spatial shape, wavelength, polarization, and a spectrum that is the Fourier transform of its temporal profile,” Senellart tells Phys.org. “As a result, to obtain near optimal single photon sources in an optoelectronic device, we had to solve many scientific and technological challenges, leading to an achievement that is the result of more than seven years of research.”

Continue reading “The path to perfection: Quantum dots in electrically-controlled cavities yield bright, nearly identical photons” »

Riding the coattails of cold atomic physics, researchers have demonstrated the ability to steer cold molecules into desired quantum states.

Ultracold atoms have become a favorite tool in physics because they can be precisely placed in a quantum state using optical and magnetic fields. This quantum control has been crucial for understanding fundamental quantum-mechanical behavior and for creating metrological devices such as the atomic clocks that keep time for GPS systems. Current efforts are devoted to using these controllable systems to simulate, for example, superconductivity, but this and other future applications will likely require that the particles within the system interact with each other. Ultracold atoms do not interact very strongly, so an obvious alternative is to turn to molecules. As opposed to atoms, molecules can have an electric dipole, which lets them naturally interact strongly with each other through dipole forces. But molecules are not a straight substitute for atoms. They are much more complicated and thus significantly harder to cool and control than atoms.

“We are reaching the limits of how precisely we can test quantum theory on Earth,” says Daniel Oi at the University of Strathclyde. Researchers from the National University of Singapore (NUS) and the University of Strathclyde, UK, have become the first to test in orbit technology for satellite-based quantum network nodes. With a network that carries information in the quantum properties of single particles, you can create secure keys for secret messaging and potentially connect powerful quantum computers in the future. But scientists think you will need equipment in space to get global reach.

Another reliable article on the Quantum Internet work.

You can’t sign up for the quantum internet just yet, but researchers have reported a major experimental milestone towards building a global quantum network — and it’s happening in space.

With a network that carries information in the quantum properties of single particles, you can create secure keys for secret messaging and potentially connect powerful quantum computers in the future. But scientists think you will need equipment in space to get global reach.

Continue reading “Quantum satellite device tests technology for global quantum network” »

Scientists at Ludwig-Maximilians-Universitaet (LMU) in Munich and the Max Planck Institute for Quantum Optics (MPQ) have devised a new interferometer to probe the geometry of band structures.

The geometry and topology of electronic states in solids play a central role in a wide range of modern condensed-matter systems, including graphene and topological insulators. However, experimentally accessing this information has proven to be challenging, especially when the bands are not well isolated from one another. As reported by Tracy Li et al. in last week’s issue of Science (Science, May 27, 2016, DOI: 10.1126/science.aad5812), an international team of researchers led by Professor Immanuel Bloch and Dr. Ulrich Schneider at LMU Munich and the Max Planck Institute of Quantum Optics has devised a straightforward method with which to probe band geometry using ultracold atoms in an optical lattice. Their method, which combines the controlled transport of atoms through the energy bands with atom interferometry, is an important step in the endeavor to investigate geometric and topological phenomena in synthetic band structures.

A wide array of fundamental issues in condensed-matter physics, such as why some materials are insulators while others are metals, can be understood simply by examining the energies of the material’s constituent electrons. Indeed, band theory, which describes these electron energies, was one of the earliest triumphs of quantum mechanics, and has driven many of the technological advances of our time, from the computer chips in our laptops to the liquid-crystal displays on our smartphones. We now know, however, that traditional band theory is incomplete.

Continue reading “Solid-state physics: Probing the geometry of energy bands” »

Researchers from the University of Bristol have used acoustics to make gauntlets that are able to levitate particles.

It seems that Earth is closer to Timelord technology than ever—particularly after a team of researchers from the University of Bristol in England unveiled their latest invention: the GauntLev.

The GauntLev functions similar to Doctor Who’s infamous sonic screwdriver. Well, almost. Timelord sonic screwdrivers can pick locks and disarm weapons, scan matter, and do a bunch of other cool stuff. Earthling sonic screwdrivers can levitate objects using sound waves.

Continue reading “Scientists Just Used Sound Waves to Make Gauntlets of Levitation” »

Researchers used high-purity graphene and observed for the first time that its charged particles behave like fluid with relativistic properties. This discovery holds promise for thermoelectric devices as well as for studying the behavior of black holes and celestial bodies.

( Peter Allen/Harvard SEAS )

Electrons in graphene appear for the first time to behave like a liquid, potentially leading to devices that can efficiently convert heat to electricity and chips that can precisely model the behavior of black holes and high-energy celestial objects.

Continue reading “Graphene That Behaves Like Water Can Pave Way For Chips That Can Model Black Hole, Supernova Behaviors” »

Wonderful! We’re well on our way of making QC more available on many devices in the near future.

Creating quantum computers which some people believe will be the next generation of computers, with the ability to outperform machines based on conventional technology—depends upon harnessing the principles of quantum mechanics, or the physics that governs the behavior of particles at the subatomic scale. Entanglement—a concept that Albert Einstein once called “spooky action at a distance”—is integral to quantum computing, as it allows two physically separated particles to store and exchange information.

Stevan Nadj-Perge, assistant professor of applied physics and materials science, is interested in creating a device that could harness the power of entangled particles within a usable technology. However, one barrier to the development of quantum computing is decoherence, or the tendency of outside noise to destroy the quantum properties of a quantum computing device and ruin its ability to store information.

Continue reading “Engineering nanodevices to store information the quantum way” »

When someone mentions “different dimensions,” we tend to think of things like parallel universes — alternate realities that exist parallel to our own, but where things work or happened differently. However, the reality of dimensions and how they play a role in the ordering of our Universe is really quite different from this popular characterization.

To break it down, dimensions are simply the different facets of what we perceive to be reality. We are immediately aware of the three dimensions that surround us on a daily basis – those that define the length, width, and depth of all objects in our universes (the x, y, and z axes, respectively).

Beyond these three visible dimensions, scientists believe that there may be many more. In fact, the theoretical framework of Superstring Theory posits that the universe exists in ten different dimensions. These different aspects are what govern the universe, the fundamental forces of nature, and all the elementary particles contained within.

Continue reading “Understanding A 10 Dimensional Universe” »