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.”

Micro-macro entangled 'cat states' could one day test quantum gravity

Micro-macro entangled 'cat states' could one day test quantum gravity: The proposed method involves storing one component of an entangled state of light (consisting of just one or a few photons) in a mechanical resonator (consisting of billions of atoms). During this process, the initial microscopic entangled state of photons is amplified with a strong coherent beam, the photons are converted into phonons, and then the entangled states are retrieved.
This approach makes it possible to create optomechanical "cat states," in which the quantum states of the photons and phonons are in superposition.

First step towards 'programmable materials'

First step towards 'programmable materials': The working model used by the researchers consists of a one-meter by one-centimeter aluminum plate that is one millimeter thick. This sheet-metal strip can vibrate at different frequencies. In order to control the wave propagation, ten small aluminum cylinders (7 mm thick, 1 cm high) are attached to the metal. Between the sheet and the cylinders sit piezo discs, which can be stimulated electronically and change their thickness in a flash. This ultimately enables the team headed by project supervisor Andrea Bergamini to control exactly whether and how waves are allowed to propagate in the sheet-metal strip. The aluminum strip thus turns into a so-called adaptive phononic crystal – a material with adaptable properties.

How To Steer Sound Using Light - Technology Review

How To Steer Sound Using Light - Technology Review: Zap an optical fibre with a couple of laser beams and the resulting interference pattern causes an interesting effect--it squeezes the material, an effect known as electrostriction...
Not to be outdone, phonons also influence light because they change the refractive index of the material. This bends light and alters its frequency, an effect known as Brillouin scattering...
They say that the light ends up guiding the phonons that it creates. In other words, it's possible to create and then steer sound using light. "The phonon wavepacket generated via [electrostriction] is naturally guided by the light that gave it birth," say Beugnot and Laude.

A Final Answer on How High-Temperature Superconductors Don't Work?

A Final Answer on How High-Temperature Superconductors Don't Work?: Tiny vibrations called phonons—the essential ingredient in the mechanism behind ordinary superconductors-play no significant role in high-temperature superconductivity, the team claims...

But theorists say phonons do not pull hard enough to keep electrons paired at the sky-high temperatures—which are still far below the freezing point of water—achieved in high-temperature superconductors. Instead, many think the glue originates in interactions among the electrons themselves, such as waves of magnetism called spin fluctuations...

The team hit the sample with a one-two punch of laser pulses roughly 100 millionths of a nanosecond, or 100 femtoseconds, long. The first pulse stirred up the electrons in the material; the second pulse measured how much the material's reflectivity had changed. The team was also able to trace the reaction not only in time, but also as a function of the frequency of the reflected light...

The ability to study the reflectivity at different wavelengths was key, Giannetti says. That's because the ultrafast electron-electron processes were too fast to observe in the time traces. However, those processes affect the reflectivity at different wavelengths in different ways—100 femtoseconds after the pulse the material was less reflective at longer wavelengths and more reflective at shorter wavelengths. Taken all together, the data show that phonons aren't needed to explain BSCCO's superconductivity, Giannetti says. Electron-electron interactions are strong enough to do the job all by themselves.

Mechanical micro-drum cooled to quantum ground state

Mechanical micro-drum cooled to quantum ground state: the NIST experiments nearly stop the beating motion of a microscopic aluminum drum made of about 1 trillion atoms, placing the drum in a realm governed by quantum mechanics with its energy below a single quantum, or one unit of energy. Like a plucked guitar string that plays the same tone while the sound dissipates, the drum continues to beat 11 million times per second, but its range of motion approaches zero...

In the NIST experiments, the drum is first chilled in a cryogenic refrigerator using liquid helium. This lowers the drum energy to about 30 quanta. Sideband cooling then reduces the drum temperature from 20 milliKelvin (thousandths of a degree above absolute zero) to below 400 microKelvin (millionths of a degree above absolute zero), steadily lowering the drum energy to just one-third of 1 quantum.
Scientists begin the sideband cooling process by applying a drive tone to the circuit at a particular frequency below the cavity resonance. The drumbeats generate sideband photons, which naturally convert to the higher frequency of the cavity...

Making materials to order

Making materials to order: A team of researchers at MIT has found a way to make complex composite materials whose attributes can be fine-tuned to give various desirable combinations of properties such as stiffness, strength, resistance to impacts and energy dissipation.

The key feature of the new composites is a “co-continuous” structure of two different materials with very different properties, creating a material combining aspects of both. The co-continuous structure means that the two interleaved materials each form a kind of three-dimensional lattice whose pieces are fully connected to each other from side to side, front to back, and top to bottom...

The process could even be used to make materials with "tunable" properties: for example, to allow certain frequencies of phonons — waves of heat or sound — to pass through while blocking others, with the selection of frequencies tuned through changes in mechanical pressure. It could also be used to make materials with shape-memory properties, which could be compressed and then spring back to a specific form.

Superconductivity's Smorgasbord of Insights: A Movable Feast

Superconductivity's Smorgasbord of Insights: A Movable Feast: Physicists have applied the theory of superconductivity directly to nuclear matter, liquid helium, and ultracold atomic gases. Historically, insights from superconductivity convinced theorists of the importance of symmetries and the ways in which a physical system can muddle or “break” them. The concept of “spontaneous symmetry breaking” now undergirds theory in many fields, especially particle physics. “It was not a way that people were thinking, certainly not in elementary particle physics,” says Gordon Baym, a theorist at the University of Illinois, Urbana-Champaign. Superconductivity, he says, “changed the way people thought in different fields..."


The BCS model was more than a one-trick pony. Bardeen, Cooper, and Schrieffer had based it on just two assumptions: that the particles are fermions and that they attract each other. So “it was obvious to all of us” that the theory would apply to other particles interacting through different forces, Cooper says.
First came applications to atomic nuclei. In the summer of 1957, before the BCS theory was published, Pines visited the University of Copenhagen. There he, Aage Bohr (Niels Bohr's son), and Ben Mottelson found they could explain long-standing puzzles, such as why nuclei with an even number of protons and even number of neutrons are particularly tightly bound. The protons and neutrons, also fermions, independently pair.

Quantum Whirls - Science News

Quantum Whirls - Science News: ...His experiments involved spinning a cylinder the size of a skateboard and watching how the liquid helium sloshed inside.
Frustrated that none of the tracer particles he could buy would float, he created a new technique to freeze hydrogen, the only element lighter than helium, into a fog of ice particles. He sprinkled the hydrogen particles like snow onto the helium. They floated...
...Bewley shined a laser onto the supercold liquid with the hydrogen snow. He was shocked to see Feynman’s vortices pop into existence and bump into each other. A few days later, he and his adviser caught the whole dance on tape...
...The way that vortices snapped away from each other is similar to how Drake imagined magnetic field lines twisting in the sun...

How long does a tuning fork ring? 'Quantum-mechanics' solve a very classical problem

How long does a tuning fork ring? 'Quantum-mechanics' solve a very classical problem: For many of these applications it is necessary to minimize the mechanical loss. However, it had previously remained a challenge to make numerical predictions of the attainable Q for even relatively straightforward geometries. Researchers from Vienna and Munich have now overcome this hurdle by developing a finite-element-based numerical solver that is capable of predicting the design-limited damping of almost arbitrary mechanical resonators. "We calculate how elementary mechanical excitations, or phonons, radiate from the mechanical resonator into the supports of the device"

Physicists create sonic black hole in the lab

Physicists create sonic black hole in the lab: The researchers created the sonic black hole in a Bose-Einstein condensate made of 100,000 rubidium atoms slowed to their lowest quantum state in a magnetic trap. This cold cluster of atoms acts like a single, large quantum mechanical object. In order to transform this condensate into a sonic black hole, the scientists had to find a way to accelerate some of the condensate to supersonic speeds so that the condensate would contain some regions of supersonic flow and some regions of subsonic flow.

The scientists achieved this acceleration by shining a large-diameter laser on the condensate in such a way as to create a steplike potential and a harmonic potential. When the condensate crosses the “step” in the steplike potential, the condensate accelerates to supersonic speeds. The scientists demonstrated that the condensate could accelerate to more than an order of magnitude faster than the speed of sound.

Novel metamaterial vastly improves quality of ultrasound imaging

Novel metamaterial vastly improves quality of ultrasound imaging: "The researchers refer to their device for capturing evanescent waves as a three-dimensional, holey-structured metamaterial. It consists of 1,600 hollow copper tubes bundled into a 16 centimeter (6 inch) bar with a square cross-section of 6.3 cm (2.5 inches). Placed close to an object, the structure captures the evanescent waves and pipes them through to the opposite end.
In a practical device, Zhu said, the metamaterial could be mounted on the end of an ultrasound probe to vastly improve the image resolution. The device would also improve underwater sonography, or sonar, as well as non-destructive evaluation in industry applications.
'For ultrasound detection, the image resolution is generally in the millimeter range,' said co-author Xiaobo Yin. 'With this device, resolution is only limited by the size of the holes.'"

CBC News - Technology & Science - Quantum 'weirdness' used by plants, animals

CBC News - Technology & Science - Quantum 'weirdness' used by plants, animals: "Lloyd said he got into the area about 3� years ago when someone in his lab found an article in the New York Times about researchers in Berkeley, Calif., who claimed green sulphur bacteria were performing a type of quantum calculation called a quantum search process while using photosynthesis to turn sunlight into energy."

Breaking the noise barrier: Enter the phonon computer - tech - 05 October 2010 - New Scientist

Breaking the noise barrier: Enter the phonon computer: Physicists have already shown that the phonons in a row of ions can behave rather like a computer. Information can be "written" to one ion by zapping it with a laser to change its state. This also modifies the electric forces between the ions, changing the way the row vibrates. Phonons, representing the collective motion of the row, in effect share the data between the ions, allowing them to "process" it. When processing is complete, the ions can be made to release the "answer" as a photon.

Scientists examine possibility of a phonon laser, or 'phaser'

Scientists examine possibility of a phonon laser, or 'phaser': "In the new method, the gas is confined in a magneto-optical trap. Three physical processes are used to create the phonon laser instability. First, a red-detuned laser beam cools the atomic gas to ultra-cold temperatures. Then, a blue-detuned laser pumps the ultra-cold atomic gas to create a population inversion, which is also a standard requirement for optical lasers. Finally, the atoms produce a coherent emission of phonons and then decay into a lower kinetic energy state. The scientists note that the resulting acoustic oscillations can then be coupled to the outside world by mechanical or electromagnetic means, where they could be used to provide a source of coherent acoustic radiation."

Technology Review: Blogs: arXiv blog: Quantum Entanglement Holds DNA Together, Say Physicists

Technology Review: Blogs: arXiv blog: Quantum Entanglement Holds DNA Together, Say Physicists

"That's possible because phonons have a wavelength which is similar in size to a DNA helix and this allows standing waves to form, a phenomenon known as phonon trapping. When this happens, the phonons cannot easily escape. A similar kind of phonon trapping is known to cause problems in silicon structures of the same size."

Lasing Beyond Light

Physicists focus on whole new types of waves, from beams of sound and plasma swells to looking for ripples in spacetime -

http://www.sciencenews.org/view/feature/id/58504/title/Lasing_Beyond_Light

Quantum leap for phonon lasers

Quantum leap for phonon lasers: "Light and sound are similar in various ways: they both can be thought of in terms of waves, and they both come in quantum mechanical units (photons in the case of light, and phonons in the case of sound). In addition, both light and sound can be produced as random collections of quanta (consider the light emitted by a light bulb) or orderly waves that travel in coordinated fashion (as is the case for laser light). Many physicists believed that the parallels imply that lasers should be as feasible with sound as they are with light. "

Invisibility cloak could hide buildings from quakes - tech - 26 June 2009 - New Scientist

Invisibility cloak could hide buildings from quakes: The new theoretical cloak comprises a number of large, concentric rings made of plastic fixed to the Earth's surface. The stiffness and elasticity of the rings must be precisely controlled to ensure that any surface waves pass smoothly into the material, rather than reflecting or scattering at the material's surface.

When waves travel through the cloak they are compressed into tiny fluctuations in pressure and density that travel along the fastest path available. By tuning the cloak's properties, that path can be made to be an arc that directs surface waves away from an area inside the cloak. When the waves exit the cloak, they return to their previous, larger size.

Unlike some of the optical invisibility cloaks that have been studied in physics labs in recent years, the new cloak is "broadband", meaning that it can divert waves across a range of frequencies.