Lasers make fibre optic tubes out of thin air - tech - 22 July 2014 - New Scientist

Lasers make fibre optic tubes out of thin air - tech - 22 July 2014 - New Scientist: The team shone four lasers in a square arrangement, heating air molecules and creating a low-density ring around a denser core of air. Light bounces around the dense core just like in a fibre.

The air fibre lasts for a few milliseconds – more than enough to send a signal.

First Movie Of An Entire Brain’s Neuronal Activity — The Physics arXiv Blog — Medium

First Movie Of An Entire Brain’s Neuronal Activity — The Physics arXiv Blog — Medium: ...Schrödel, Prevedel and co developed a way to ensure that the genes only fluoresce in the nucleus of each neuron. That makes active neurons much easier to tell apart...

...light sculpting. This works by bouncing the spot of laser light off a grating that stretches it out. This creates a disc of light that images an area of the brain in one go rather than a single point. In affect, it produces a cross-sectional image of brain activtiy.

The advantage is that the light disc need only be scanned in one direction to capture the whole volume of the brain. And this can be done at a rate that allows the team to film the neuronal activity of the entire brain at a rate of 80 frames per second.

Ultrasonic imaging at 1,000 times times higher resolution | KurzweilAI

Ultrasonic imaging at 1,000 times times higher resolution | KurzweilAI: The researchers used a combination of subpicosecond laser pulses and unique nanostructures to produce acoustic phonons... at a frequency of 10 gigahertz (10 billion cycles per second).

By comparison, medical ultrasounds devices today typically reach a frequency of only about 20 megahertz...

“To generate 10 GHz acoustic frequencies in our plasmonic nanostructures we use a technique known as picosecond ultrasonics,” said author are Kevin O’Brien. “Sub-picosecond pulses of laser light excite plasmons which dissipate their energy as heat. The nanostructure rapidly expands and generates coherent acoustic phonons. This process transduces photons from the laser into coherent phonons.”

Long-range tunneling of quantum particles

Long-range tunneling of quantum particles: Experimental physicists in Innsbruck, Austria, have now directly observed quantum particles transmitting through a whole series of up to five potential barriers under conditions where a single particle could not do the move.

Continuous terahertz sources demonstrated at room temperature

Continuous terahertz sources demonstrated at room temperature: They have developed the first room-temperature, compact, continuous terahertz radiation source, and it's six times more efficient than previous systems...

The team generated terahertz radiation through nonlinear frequency mixing of two mid-infrared wavelengths at 8.8 microns and 9.8 microns from a single QCL chip. Room temperature, continuous terahertz emission with 3 microwatts is realized in a monolithic nonlinear QCL device with a tiny packaging dimension (as small as 2x5x8 mm3). This is achieved by improving the thermal conductance with epilayer-down bonding and a buried ridge waveguide, as well as by decreasing the optical loss with a buried composite grating for stable, single mode operation.

Researchers develop three-step process for building fractal nanostructures

Researchers develop three-step process for building fractal nanostructures: Greer's group has developed a three-step process for building such complex structures very precisely. They first use a direct laser writing method called two-photon lithography to "write" a three-dimensional pattern in a polymer, allowing a laser beam to crosslink and harden the polymer wherever it is focused. At the end of the patterning step, the parts of the polymer that were exposed to the laser remain intact while the rest is dissolved away, revealing a three-dimensional scaffold. Next, the scientists coat the polymer scaffold with a continuous, very thin layer of a material—it can be a ceramic, metal, metallic glass, semiconductor, "just about anything," Greer says. In this case, they used alumina, or aluminum oxide, which is a brittle ceramic, to coat the scaffold. In the final step they etch out the polymer from within the structure, leaving a hollow architecture.

New ‘switch’ could power quantum computing | MIT News Office

New ‘switch’ could power quantum computing | MIT News Office:  “We have demonstrated basically an atom can switch the phase of a photon. And the photon can switch the phase of an atom...”

In this case, the researchers used a laser to place a rubidium atom very close to the surface of a photonic crystal cavity, a structure of light. The atoms were placed no more than 100 or 200 nanometers — less than a wavelength of light — from the edge of the cavity. At such small distances, there is a strong attractive force between the atom and the surface of the light field, which the researchers used to trap the atom in place...

“In some sense, it was a big surprise how simple this solution was compared to the different techniques you might envision of getting the atoms there,” Vuletić says.

How the U.S. Built the World’s Most Ridiculously Accurate Atomic Clock | Science | WIRED

How the U.S. Built the World’s Most Ridiculously Accurate Atomic Clock | Science | WIRED: Both NIST-F2 and the standard it replaces, NIST-F1, are known as cesium-based atomic fountain clocks...

The previous generation of atomic clock was already quite good at figuring out the length of a second but had a few small sources of error. NIST-F1 operates at room temperature and so the walls of the chamber in which the cesium atom ball is tossed heat up, emitting a small amount of radiation. This interferes with the atoms, causing them to shift ever so slightly in their energy levels. By cooling NIST-F2 with liquid nitrogen, the new timepiece reaches temperatures of – 316 degrees Fahrenheit, virtually eliminating this excess radiation and reducing the shifting 100-fold.

Orbital computing: An amazing atomic-level tech for future computers | ExtremeTech

Orbital computing: An amazing atomic-level tech for future computers | ExtremeTech: He calls the idea “orbital computing” since the bit... would be the orbits of electrons around the nucleus of an atom. The goal is to be able to probe the electron clouds of single atoms using terahertz waves of just the right size.

In materials like these, the macroscopic properties (like conductance) are controlled mainly by electron orbits known as “d-orbitals.” The state of these d-orbitals can be readily observed with X-rays, and they can be controlled as easily as adjusting the temperature. But temperature or other gross manipulations are relatively slow ways to try to read or write data, compact bunches of T-rays does the trick much better.

A black hole in a bath: Big physics on a bench-top - physics-math - 10 March 2014 - New Scientist

A black hole in a bath: Big physics on a bench-top - physics-math - 10 March 2014 - New Scientist

Supersymmetry...  One of its central predictions is that there should be more than one Higgs particle... they might have found some clue as to where those extra particles might be – in superfluid helium-3... The discovered Higgs weighs in at around 125 gigaelectronvolts (GeV). Studying the spectrum of excitations in the superfluid helium suggests Higgs particles should also exist at energies of 210 GeV and 325 GeV. These possibilities are not excluded by results collected so far at the LHC...

By concentrating laser light into a very small spot within a waveguide made of a glass block, he can temporarily change the refractive index of the glass so that it slows down subsequent laser pulses and ultimately repels them. "What makes these analogue experiments so powerful is that from a photon or a water wave's perspective, it has no way of distinguishing whether it is crossing the event horizon of a real black hole or is in a waveguide under some weird constraints," he says.

New generation laser will herald technological breakthrough

New generation laser will herald technological breakthrough: In a paper recently published in Physical Review B, researchers from the Department of Physics demonstrate their work into bosonic lasers which emit terahertz radiation.
Such lasers have been around for years, commonly found in satellites, for environmental monitoring, astronomy, security and non-destructive testing, imaging, and medical applications. But they are considered bulky, impractical and expensive.

Speed limit on a superfluid helium nano-highway

Speed limit on a superfluid helium nano-highway: The new research has now shown that even in tiny nanodroplets, helium still exhibits superfluidity...


The result of the experiment was quite astonishing: the measured velocity is always the same. It does not matter whether the impurity is a metal atom, a diatomic molecule or a polyatomic molecule with a cage structure: they all leave the droplet with the same speed. Mass or size thus does not matter. Even the repulsive force (which could be tuned with the laser pulse) turned out not to be of any influence.

Two-laser boron fusion lights the way to radiation-free energy : Nature News & Comment

Two-laser boron fusion lights the way to radiation-free energy : Nature News: One laser created a short-lived plasma, or highly ionized gas of boron nuclei, by heating boron atoms; the other laser generated a beam of protons that smashed into the boron nuclei, releasing slow-moving helium particles but no neutrons...

The boron plasma generated by the laser lasts only about one-billionth of a second, and so the pulse of protons, which lasts one-trillionth of a second, must be precisely synchronized to slam into the boron target. The proton beam is preceded by a beam of electrons, generated by the same laser, that pushes away electrons in the boron plasma, allowing the protons more of a chance to collide with the boron nuclei and initiate fusion.

'Accelerator on a chip' demonstrated

'Accelerator on a chip' demonstrated: ...electrons are first accelerated to near light-speed in a conventional accelerator. Then they are focused into a tiny, half-micron-high channel within a fused silica glass chip just half a millimeter long. The channel had been patterned with precisely spaced nanoscale ridges. Infrared laser light shining on the pattern generates electrical fields that interact with the electrons in the channel to boost their energy.

Scientists create never-before-seen form of matter

Scientists create never-before-seen form of matter: What we have done is create a special type of medium in which photons interact with each other so strongly that they begin to act as though they have mass, and they bind together to form molecules...


An effect called a Rydberg blockade, Lukin said, which states that when an atom is excited, nearby atoms cannot be excited to the same degree. In practice, the effect means that as two photons enter the atomic cloud, the first excites an atom, but must move forward before the second photon can excite nearby atoms.

The result, he said, is that the two photons push and pull each other through the cloud as their energy is handed off from one atom to the next.

"It's a photonic interaction that's mediated by the atomic interaction..."

Physicists Net Fractal Butterfly: Scientific American

Physicists Net Fractal Butterfly: Scientific American: ...the pattern describes the behavior of electrons in extreme magnetic fields...

...It was known at the time that electrons under the influence of a magnetic field would race around in circles. But Hofstadter found that in theory, if the electrons were confined inside a crystalline atomic lattice, their motion would become complicated. As the magnetic field was cranked up, the energy levels that define the motion of electrons would split again and again. When represented on a graph, those energy levels revealed a pattern that looked like a butterfly — and continued to do so, even when zoomed in to infinitely small scales...

 In May, researchers reported that they had stacked a single sheet of graphene, in which carbon atoms are arranged like a honeycomb, on top of a sheet of honeycombed boron nitride. The layers create a repeating pattern that provides a larger target for magnetic fields than the hexagons in each material — effectively magnifying the field.

New Measurement of Gravitational Constant Comes Up Higher Than Expected - Wired Science

New Measurement of Gravitational Constant Comes Up Higher Than Expected - Wired Science: The team, led by Terry Quinn, the former director of the International Bureau of Weights and Measures in France, used an updated version of Cavendish’s setup for one experiment. But they conducted an additional experiment, using a servo to counteract the twisting of the wire and figuring out the gravitational constant based on the voltage required to keep their apparatus from moving. Taken together, their tests yielded a new G value of 6.67545 × 10−11 m3⁄kg s2, which is higher than the current accepted value by about 240 parts per million.

Fastest rotating man-made object created

Fastest rotating man-made object created: To do this they manufactured a microscopic sphere of calcium carbonate only 4 millionths of a metre in diameter. The team then used the miniscule forces of laser light to hold the sphere with the radiation pressure of light...
They exploited the property of polarisation of the laser light that changed as the light passed through the levitating sphere, exerting a small twist or torque.
Placing the sphere in vacuum largely removed the drag (friction) due to any gas environment, allowing the team to achieve the very high rotation rates...

"I am intrigued with the prospect of extending this to multiple trapped particles and rotating systems. We may even be able to shed light on the area of quantum friction – that is – does quantum mechanics put the brakes on the motion or spinning particle even though we are in a near perfect vacuum with no other apparent sources of friction?"

Video: Near-Whole Brain Activity Map in Fish | MIT Technology Review

Video: Near-Whole Brain Activity Map in Fish | MIT Technology Review: ...researchers reported that they were able to watch the individual activity of nearly all the neurons in a fish’s brain at the same time...

Now, HHMI has put together a video about the work, and it’s worth a look. Neuroscientist Philipp Keller explains how some of the technology behind the experiment works. Best of all, we get to see more of the complex flickering constellations of brain cells—fish thoughts in action. This work is the first time researchers have been able to look at the activity of nearly all neurons in a vertebrate brain.

NIST Ytterbium Atomic Clocks Set Record for Stability

NIST Ytterbium Atomic Clocks Set Record for Stability: The ytterbium clock ticks are stable to within less than two parts in 1 quintillion (1 followed by 18 zeros), roughly 10 times better than the previous best published results for other atomic clocks...
Each of NIST's ytterbium clocks relies on about 10,000 rare-earth atoms cooled to 10 microkelvin (10 millionths of a degree above absolute zero) and trapped in an optical lattice—a series of pancake-shaped wells made of laser light. Another laser that "ticks" 518 trillion times per second provokes a transition between two energy levels in the atoms. The large number of atoms is key to the clocks' high stability.
The ticks of any atomic clock must be averaged for some period to provide the best results. One key benefit of the very high stability of the ytterbium clocks is that precise results can be achieved very quickly. For example, the current U.S. civilian time standard, the NIST-F1 cesium fountain clock, must be averaged for about 400,000 seconds (about five days) to achieve its best performance. The new ytterbium clocks achieve that same result in about one second of averaging time.