Physicist proves impossibility of quantum time crystals

Physicist proves impossibility of quantum time crystals: Bruno explains that this proof should not come as a surprise, since a 1964 theory by another Nobel Laureate, Walter Kohn, shows that an insulator is completely insensitive to a magnetic flux. Since quantum time crystals are modeled as ring-shaped Wigner crystals, and Wigner crystals are insulators, attempting to show that a magnetic flux can cause such a system to rotate is, as Bruno writes, "a hopelessly doomed endeavor."

New prototype device recognizes electrical properties of infected cells as signatures of disease

New prototype device recognizes electrical properties of infected cells as signatures of disease: Several types of infection, including malaria, alter a cell's impedance...

To find out, first authors... built a microfluidic device capable of measuring the magnitude and phase of the electrical impedance of individual cells. The device is essentially a cell-counting device, similar in approach to other low-cost, portable devices being developed to diagnose illnesses such as HIV.
The challenge, however, involved optimizing the electronics to allow very accurate measurements of impedance for each cell as it passes by...
In tests of cells of four cell types—uninfected cells and infected cells at the ring, trophozoite and schizont stages—the device detected small differences in measures of magnitude and seemingly random differences in phase, but not quite enough to definitively differentiate among stages.
However, by mathematically combining the measures into an index called delta, the differences between uninfected cells and all three stages became clear.

Researchers find way to measure speed of spinning object using light's orbital angular momentum

Researchers find way to measure speed of spinning object using light's orbital angular momentum: In this new effort, the researchers found a way to measure the spin speed of an object that is not observed at an angle by taking advantage of a characteristic of light known as orbital angular momentum (OAM). This is where electromagnetic energy associated with light flows forward in the direction of propagation while also continuously moving around its own axis. In essence, it's light moving through space like a corkscrew. The researchers found that light can be imbued with OAM if it is reflected off a rotating object and it was this discovery that led to its use in calculating the spin speed of the object. Specifically, they found they could calculate the spin speed of the object by measuring the OAM in the light that has been reflected back by it.

To test their theory, the researchers fired a laser at a spinning plate in their lab then used a light detector to measure the degree of OAM. Because the plate was spinning, it gave off both positive and negative OAM—the degree of difference between the two gave the researchers the speed of rotation of the object.

A Snapshot of the Inside of an Atom - ScienceNOW

A Snapshot of the Inside of an Atom - ScienceNOW: ...the team first fired two lasers at hydrogen atoms inside a chamber, kicking off electrons at speeds and directions that depended on their underlying wave functions. A strong electric field inside the chamber guided the electrons to positions on a planar detector that depended on their initial velocities rather than on their initial positions. So the distribution of electrons striking the detector matched the wave function the electrons had at the moment they left their hydrogen nuclei behind. The apparatus displays the electron distribution on a phosphorescent screen as light and dark rings, which the team photographed using a high-resolution digital camera.

First Demonstration of the Storage And Release of Light in a Metamaterial

First Demonstration of the Storage And Release of Light in a Metamaterial: In this case, Nakanishi and co have created a metamaterial in which each repeating unit contains two variable capacitors. One of the capacitors is designed to absorb and radiate waves at a particular frequency while the other is designed to trap them.

If the capacitors are tuned to the same frequency, any light at that frequency is absorbed and trapped. Detuning the capacitors then releases the electromagnetic waves, allowing them to continue on their way...


What’s more impressive, however, is that the released waves have the same phase distribution as the originals. “The electromagnetic waves were stored and released, while maintaining the phase distribution in the propagating direction,” they say.

Graphene Antennas Would Enable Terabit Wireless Downloads

Graphene Antennas Would Enable Terabit Wireless Downloads: To make an antenna, the group says, graphene could be shaped into narrow strips of between 10 and 100 nanometers wide and one micrometer long, allowing it to transmit and receive at the terahertz frequency, which roughly corresponds to those size scales. Electromagnetic waves in the terahertz frequency would then interact with plasmonic waves—oscillations of electrons at the surface of the graphene strip—to send and receive information.

Bumblebees Sense Electric Fields in Flowers

Bumblebees Sense Electric Fields in Flowers: Finally, the team released bumblebees into an arena with artificial flowers, half of which were positively charged and carried a sucrose reward, and the other half of which were grounded and carried a bitter solution. Over time, the bees increasingly visited the rewarding charged flowers.

But when the researchers turned off the electrical charge on the flowers and re-released the trained bees, the insects visited rewarding flowers only about half of the time, as they would have by random chance.

Data waves keep your wearable tech in tune

Data waves keep your wearable tech in tune: Now a new wireless technique that uses a phenomenon known as Zenneck surface waves could be the answer.

This type of electromagnetic wave stays at the interface between the surface of an object and the air, rather than travelling through open space. Radar systems have used them to see around the curvature of the Earth, but communicating in this way is a first.

Metamaterials experts show a way to reduce electrons' effective mass to nearly zero

Metamaterials experts show a way to reduce electrons' effective mass to nearly zero: Their idea was born out of the similarities and analogies between the mathematics that govern electromagnetic waves—Maxwell's Equations—and those that govern the quantum mechanics of electrons—Schrödinger's Equations...


A semiconductor's qualities stem from the lattice-like pattern its constituent atoms are arranged in; an electron must navigate the electric potentials of all of these atoms, moving faster or slower depending on how directly it can pass by them. Esaki and his colleagues showed that, by making a superlattice out of layers of different materials, they could produce a composite material that had different electron transport properties than either of the components...

Turning Pull Into Push? - ScienceNOW

Turning Pull Into Push? - ScienceNOW: To see how this scenario works, consider the case in which just a point charge moves across the surface of an insulator. In that case, the polarization pattern moves with it, becoming so-called evanescent waves that still attract the point charge.

If the point charge moves fast enough, another factor comes into play. In an insulating material such as glass, light travels slower than in empty space. And if a charge moves through the glass faster than light can, it creates a shockwave of light, known as Cherenkov radiation, much like the sonic boom from a supersonic jet. Now, if a point charge above the insulator whizzes along faster than light can within the material, then the induced polarization pattern will move that fast as well and create Cherenkov radiation. That radiation flows at an angle down into the material and carries momentum with it. But by Newton's law that every action has an equal and opposite reaction, the downward flow of momentum must be balanced by an upward push on the point charge.

Earth's magnetic field is singing. This is what it sounds like.

Earth's magnetic field is singing. This is what it sounds like.: Chorus is an electromagnetic phenomenon caused by plasma waves in Earth's radiation belts. For years, ham radio operators on Earth have been listening to them from afar. Now, NASA's twin Radiation Belt Storm Probes are traveling through the region of space where chorus actually comes from—and the recordings are out of this world.

Microwave laser fulfills 60 years of promise : Nature News & Comment

Microwave laser fulfills 60 years of promise : Nature News: He came across a decade-old publication by Japanese researchers2 suggesting that when the electrons in pentacene are excited by a laser, they configure such that the molecule could work as a maser, possibly even at room temperature...

But the researchers were filled with doubts — the whole thing seemed too easy...


The laser light excited the pentacene molecules to an energy level known as a metastable state. Then a microwave passing through the crystal triggered the molecules to relax, releasing a cascade of microwaves of the same wavelength.

It was the same principle as an optical laser. "The signal that came out of it was huge," says Oxborrow, about a hundred million times as powerful as an existing maser.

Revolutionary 'DNA Tracking Chamber' Could Detect Dark Matter� - Technology Review

Revolutionary 'DNA Tracking Chamber' Could Detect Dark Matter� - Technology Review: The dark matter headwind should be coming from the direction of Cygnus, so a suitable detector should see the direction change as the Earth rotates each day...
...Its basic detecting unit consists of a thin gold sheet with many strands of single-strand DNA hanging from it, like bead curtains or a hanging forest. Each strand of DNA is identical except for a label at the free hanging end, which identifies where on the gold sheet it sits.

The idea is that a dark matter particle smashes into a heavy gold nucleus in the sheet, sending it careering out of the gold foil and through the DNA forest.  The gold nucleus then severs DNA strands as it travels, cutting a swathe through the forest.
These strands fall onto a collecting tray below, which is removed every hour or so. The segments can then be copied many times using a polymerase chain reaction, thereby amplifying the signal a billion times over...
The entire detector consists of hundreds or thousands of these sheets sandwiched between mylar sheets, like pages in a book. In total, a detector the size of a tea chest would require about a kilogram of gold and about 100 grams of single-strand DNA.

Quantum Horse Races and Crystals of Light

Quantum Horse Races and Crystals of Light: Bloch’s team and others bring them to heel by cooling them to a temperature of nanokelvins and pouring them into an optical lattice, which, depending on your poetic frame of mind, you might call an optical egg crate or a crystal of light... The atoms are spaced perhaps 400 nanometers apart, so they reach a density of about 100 trillion atoms per cubic centimeter—which is a lot of atoms per cubic centimeter, but still only about a hundred-thousandth the density of hydrogen gas at room temperature and pressure. So these systems let physicists explore a domain they seldom otherwise enter, a frigid, sparse realm where quantum is king...

There are all sorts of other fun experiments you can do. Last year, Bloch’s team tracked the insulator-superfluid transition and showed that the system goes through a “hidden” phase of matter—a subtly patterned arrangement that conventional theory doesn’t capture...

Yet another experiment touches on the fundamental question of what determines the speed of events in the world... They began with an insulator, dialed up the interaction energy, and watched the atoms start to self-organize. A wave of activity spread though the system at twice the speed of sound. What governed the velocity was that atoms did not passively roll on the wave, but actively contributed to it. Some quantum gravity theorists have speculated that the speed of light represents the Lieb-Robinson bound of some underlying quantum system out of which space and time emerge.

Scientists switch mouse's genes off and on with radio waves

Scientists switch mouse's genes off and on with radio waves: Friedman and his colleagues coated iron oxide nanoparticles with antibodies that bind to a modified version of the temperature-sensitive ion channel TRPV1, which sits on the surface of cells. They injected these particles into tumours grown under the skins of mice, then used the magnetic field generated by a device similar to a miniature magnetic-resonance-imaging machine to heat the nanoparticles with low-frequency radio waves. In turn, the nanoparticles heated the ion channel to its activation temperature of 42 °C. Opening the channel allowed calcium to flow into cells, triggering secondary signals that switched on an engineered calcium-sensitive gene that produces insulin. After 30 minutes of radio-wave exposure, the mice's insulin levels had increased and their blood sugar levels had dropped...
Even better, the researchers have already developed a way to achieve similar, albeit weaker, results without having to inject nanoparticles at all. They have developed cells that can grow their own required nanoparticles, meaning there would be no need to give patients strange chemicals or molecules.

Graphene-based terahertz devices: The wave of the future

Graphene-based terahertz devices: The wave of the future: Researchers at the University of Notre Dame have shown that it is possible to efficiently manipulate THz electromagnetic waves with atomically thin graphene layers. This achievement, which was recently published in Nature Communications, sets the stage for development of compact, efficient and cost-effective devices and systems operating in the THz band.

Terahertz-Band Cell Phones Could See Through Walls

Terahertz-Band Cell Phones Could See Through Walls: But terahertz imaging devices require tons of energy and multiple lenses to focus light, so they are prohibitively large. Kenneth O, professor of electrical engineering at the University of Texas at Dallas, is developing new versions that would not require multiple lenses.
The key breakthrough was a new fabrication process using familiar complementary metal-oxide semiconductors, the CMOS chips that power most consumer devices. O and his team found they could build a specific type of high-speed diode, called a Schottky diode, in CMOS. These high-speed light devices can reach the THz range using standard CMOS manufacturing processes, which means they’d be fairly simple to integrate into existing devices — without major impacts on cost or size.

Cutting corners to make superconductors work better

Cutting corners to make superconductors work better: Clem and Berggren calculated the critical current in thin and narrow superconducting strips with sharp right-angle turns, 180-degree turnarounds, and more complicated geometries. They found that current crowding, which occurs at the inner corners when the current rounds sharp turns, significantly reduces the current where a voltage first appears, called the critical current. Rounded corners, according to Clem and Berggren, will significantly improve critical currents.

Scientists blast iron with lasers, and it disappears from X-rays

Scientists blast iron with lasers, and it disappears from X-rays:  Scientists took two thin sheets of the material and held it in place with carbon, which is invisible to X-rays. They placed two platinum mirrors to either side of the iron sheets. They then fired a beam of low-energy X-rays into the set-up. The beam was reflected by the platinum mirrors back and forth again and again. Trapped, it set up a standing wave in the sandwich of equipment...
When one sheet of iron was at a node, and one sheet was at an antinode (the peak or the trough), another, higher energy x-ray was shot through the entire contraption. The x-ray moved through them without interacting with either sheet of iron...

T-rays technology could help develop Star Trek-style hand-held medical scanners

T-rays technology could help develop Star Trek-style hand-held medical scanners: This new design creates a T-ray beam at low temperatures, essentially by mixing and amplifying beams of light at different wavelengths. It uses a pair of electrodes situated just 100 nanometers apart on a semiconductor substrate. Light in two different wavelengths shines on the electrodes and is funneled through the 100-nm gap. A strong current between the electrodes acts as an antenna and amplifies the light to the THz range. The T-rays can even be tuned to create a constant beam, which would be required for a T-ray scanner. The setup is two orders of magnitude stronger than existing THz systems, the researchers say in their paper, which was published this month in Nature Photonics.
Along with their efficacy at low temperatures, the best thing about this T-ray beam is its small size — it’s tiny enough to be integrated into existing silicon chips.