Atom-Scale Ohmmeter

A highly stable scanning tunneling microscope measures the electrical properties of a metal on a scale smaller than individual atoms.

A gentle touch. The needle-like tip of a scanning tunneling microscope (STM) terminates in a single atom that can touch a surface at different locations, such as on top of an atom (left) or in the “hollow” between three atoms (right). A highly stable STM that touches the surface without damaging it can measure the differences in electrical conductance among several different types of sites.

A gentle touch. The needle-like tip of a scanning tunneling microscope (STM) terminates in a single atom that can touch a surface at different locations, such as on top of an atom (left) or in the “hollow” between three atoms (right). A highly stable STM that touches the surface without damaging it can measure the differences in electrical conductance among several different types of sites.

A scanning tunneling microscope (STM) can make an image of individual atoms on a surface or move single atoms around. Now researchers have pushed the device’s precision and used it to measure the differences in electrical conductance between different locations around a single atom on a lead surface. The results could help elucidate the properties of metals and superconductors and might one day find use in nanotechnology fabrication.

An STM brings a needle-like probe—the tip of which is a single atom—extremely close to a sample surface in a vacuum. When voltage is applied, electrons can jump, or “tunnel,” across the gap, and measuring the resulting current while moving the tip across the surface leads to an image. In another STM technique, the probe tip touches the sample, allowing atoms to chemically bond with it. Researchers have used this method, known as point contact, to move atoms around like toy blocks. The point contact technique would also be appropriate for measuring electrical conductance of a material at the atomic scale, to learn how current flows in the quantum regime, where the classical Ohm’s law fails. Continue reading Atom-Scale Ohmmeter

IBM Shows Off a Quantum Computing Chip

A new superconducting chip made by IBM demonstrates a technique crucial to the development of quantum computers

When cooled down to a fraction of a degree above absolute zero, the four dark elements at the center of the circuit in the middle of this image can represent digital data using quantum mechanical effects.

When cooled down to a fraction of a degree above absolute zero, the four dark elements at the center of the circuit in the middle of this image can represent digital data using quantum mechanical effects.

A superconducting chip developed at IBM demonstrates an important step needed for the creation of computer processors that crunch numbers by exploiting the weirdness of quantum physics. If successfully developed, quantum computers could effectively take shortcuts through many calculations that are difficult for today’s computers. Continue reading IBM Shows Off a Quantum Computing Chip

Scientists slow the speed of light

Shapely photons break rules to fly slower than light

by Jacob Aron
Anyone struggling with a New Year’s fitness regime knows that you move slower when you’re out of shape. Now it seems the same is true even for light, which up until now physicists had thought travelled at a constant speed.

It’s well known that light travels more slowly when it passes through different materials. This phenomenon, known as refraction, creates optical illusions like a seemingly broken drinking straw sticking out of a glass of water. But the speed of light in a vacuum, a little under 300,000,000 metres per second, is an unwavering constant that underpins much of modern physics, including Albert Einstein’s theory of relativity. It’s so important that physicists give it a single letter: c.

Now, Miles Padgett at the University of Glasgow, UK, and his colleagues have shown this isn’t quite right. Light travelling in a plane wave – the traditional up and down squiggle you learn about in school – always travels at c, but light with a more complex wave structure travels slightly slower, by about a thousandth of a per cent.

Light on time?

The team revealed this oddity by studying two kinds of shaped light: a Bessel beam, which looks like concentric rings of light, and a Gaussian beam, which spreads out as it travels. They used an ultraviolet laser to produce pairs of photons and passed one photon through a filter to shape it into either a Bessel or Gaussian beam. Both photons travelled one metre before hitting a detector, so they should have arrived at the same time, but the shaped photon was slightly delayed.

Why does this happen? One way of thinking about it is that some of the light in a structured beam is moving in the “wrong” direction – sideways rather than forwards. This isn’t a strictly accurate picture of the energy distribution within the beam, warns Padgett, but it is a way to imagine what might be going on. “Personally I think that’s a useful concept, though the scientific rigour police might not welcome it.”

Don’t rip up your physics textbook just yet though – the implications are likely to be minor, only affecting certain short-range experiments that rely on very precise time-of-flight measurements, for example. “We’re not challenging Einstein,” says Padgett.

Hints of this effect have been seen in other experiments, but no one had quite pinned it down before, says Ulf Leonhardt at the Weizmann Institute of Science in Rehovot, Israel. “[This] is really the first clean and clear experiment where the speed of photons in structured light beams is directly measured,” he says. Now that physicists understand it, they might be able to exploit it. “I do not foresee immediate applications in the short run, but important fundamental physics always has implications and applications in the long run.”
Read more at www.newscientist.com

Video

A Lamp Whose Light Comes From Bioluminescent Bacteria

Ocean waves glowing blue in the dark of night, anyone who has ever experienced this knows how magical it looks. The phenomenon is caused by bioluminescent micro-organisms in seawater that emit light when provided with oxygen every time a wave turnes. This principle inspired Teresa van Dongen to combine her passion for design and biology in a bioluminescent light installation. Ambio balances two weights and a glass tube half-filled with a “Artificial Seawater Medium” containing a carefully selected type of these unique luminescent species. Give the lamp a gentle push every so often and the weights will keep it moving and thus glowing. Ambio is a visualization of a research on how to use nature as a source of energy.
Read more at www.wired.com

‘Smart dust’ technology could reshape space telescopes

RIT scientist and NASA Jet Propulsion Laboratory explore adaptive optical imaging

Grover Swartzlander, associate professor at RIT’s Chester F. Carlson Center for Imaging Science, is a co-investigator on an RIT and NASA team exploring a new type of space telescope with an aperture made of swarms of particles released from a canister and controlled by a laser.

Grover Swartzlander, associate professor at RIT’s Chester F. Carlson Center for Imaging Science, is a co-investigator on an RIT and NASA team exploring a new type of space telescope with an aperture made of swarms of particles released from a canister and controlled by a laser.

Telescope lenses someday might come in aerosol cans.

Scientists at Rochester Institute of Technology and the NASA Jet Propulsion Laboratory are exploring a new type of space telescope with an aperture made of swarms of particles released from a canister and controlled by a laser.

These floating lenses would be larger, cheaper and lighter than apertures on conventional space-based imaging systems like NASA’s Hubble and James Webb space telescopes, said Grover Swartzlander, associate professor at RIT’s Chester F. Carlson Center for Imaging Science and Fellow of the Optical Society of America. Swartzlander is a co-investigator on the Jet Propulsion team led by Marco Quadrelli. Continue reading ‘Smart dust’ technology could reshape space telescopes