'Solid light' could compute previously unsolvable problems - ScienceBlog.com

'Solid light' could compute previously unsolvable problems - ScienceBlog.com: To build their machine, the researchers created a structure made of superconducting materials that contains 100 billion atoms engineered to act as a single “artificial atom.” They placed the artificial atom close to a superconducting wire containing photons.
By the rules of quantum mechanics, the photons on the wire inherit some of the properties of the artificial atom – in a sense linking them. Normally photons do not interact with each other, but in this system the researchers are able to create new behavior in which the photons begin to interact in some ways like particles.
“We have used this blending together of the photons and the atom to artificially devise strong interactions among the photons,” said Darius Sadri, a postdoctoral researcher and one of the authors. “These interactions then lead to completely new collective behavior for light – akin to the phases of matter, like liquids and crystals, studied in condensed matter physics.”

‘Unparticles’ May Hold The Key To Superconductivity, Say Physicists — The Physics arXiv Blog — Medium

‘Unparticles’ May Hold The Key To Superconductivity, Say Physicists — The Physics arXiv Blog — Medium: Georgi’s concept of unparticles comes about by conjecturing that some “stuff” may have mass, energy and momentum and yet also be scale invariant...

Physicists have long known that the behaviour of electrons in high-temperature superconductors is extremely complex...

What LeBlanc and Grushin show is that under certain conditions the interaction between these entities can become scale invariant and is therefore described by the physics of unparticles. In very simple terms, when that happens, material properties such as resistance no longer depend on the length scales involved. So if electrons move without resistance on a tiny scale, they should also move without resistance on much larger scales too. Hence the phenomenon of superconductivity.

Study helps unlock mystery of high-temp superconductors

Study helps unlock mystery of high-temp superconductors: "Evidence has been accumulating that this phase supports an exotic density wave state that may be key to its existence...". A density wave forms in a metal if the fluid electrons themselves crystalize.
Using a scanning tunneling microscope (STM) to visualize the electronic structure of the oxygen sites within a superconductor, the team found a density wave with a d-orbital structure. (The electron density near each copper atom looks a bit like a daisy in the crystallized pattern.) That's especially surprising because most density waves have an s-orbital structure; their electron density is isotropic. "It's not the pattern you would expect," Lawler says.
In this research, Lawler and his colleagues focused on a member of the cuprate class of superconductors called bismuth strontium calcium copper oxide (BSCCO). "We now believe these density waves exist in all cuprates," says Lawler, a theorist whose contribution to the research involved subtle uses of the Fourier transform, a mathematical analysis that's useful when examining amplitude patterns in waves.

Cambridge team breaks superconductor world record

Cambridge team breaks superconductor world record: The Cambridge researchers managed to 'trap' a magnetic field with a strength of 17.6 Tesla - roughly 100 times stronger than the field generated by a typical fridge magnet - in a high temperature gadolinium barium copper oxide (GdBCO) superconductor, beating the previous record by 0.4 Tesla...

In order to hold in, or trap, the magnetic field, the researchers had to modify both the microstructure of GdBCO to increase its current carrying and thermal performance, and reinforce it with a stainless steel ring, which was used to 'shrink-wrap' the single grain samples. "This was an important step in achieving this result..."

...by engineering the bulk microstructure, the field is retained in the sample by so-called 'flux pinning centres' distributed throughout the material...

Scientists May Have Decoded One of the Secrets to Superconductors | Science | WIRED

Scientists May Have Decoded One of the Secrets to Superconductors | Science | WIRED: ...ripples of electrons inside the superconductors that are called charge density waves. The fine-grained structure of the waves, reported in two new papers by independent groups of researchers, suggests that they may be driven by the same force as superconductivity. Davis and his colleagues directly visualized the waves in a study posted online in April...

It seemed possible that if the force shaping electrons into charge density waves could be suppressed, its rival, the force that forms superconducting pairs, would flourish. But some researchers argued that the ripples of electrons were merely a surface anomaly and irrelevant to superconductivity.

The community remained divided until 2012, when two groups using a technique called resonant X-ray scattering managed to detect charge density waves deep inside cuprates, cementing the importance of the waves...

The Astounding Link Between the P≠NP Problem and the Quantum Nature of Universe — The Physics arXiv Blog — Medium

The Astounding Link Between the P≠NP Problem and the Quantum Nature of Universe — The Physics arXiv Blog — Medium: ...He says the key is to think of Schrodinger’s cat as a problem of computational complexity theory...

...He says there is an implicit assumption when physicists say that Schrödinger’s equation can describe macroscopic systems. This assumption is that the equations can be solved in a reasonable amount of time to produce an answer...

If P ≠ NP and there is no efficient algorithm for solving Schrödinger’s equation, then there is only one way of finding a solution, which is a brute force search...

So the number of elementary operations needed to exactly solve this equation would be equal to 2^10^24...

...this time scale is considerably shorter than the Planck timescale, which is roughly equal to 10^-43 seconds.

Graphene superconducting property discovered | KurzweilAI

Graphene superconducting property discovered | KurzweilAI: Scientists at... SLAC... have discovered how graphene... is superconducting in a graphene-calcium compound...

While it’s been known for nearly a decade that this combined material is superconducting, the new study offers the first compelling evidence that the graphene layers are instrumental in this process...

Researchers used a beam of intense ultraviolet light to look deep into the electronic structure of CaC6.

The purity of the sample combined with the high quality of the ultraviolet light beam allowed them to see deep into the material and distinguish what the electrons in each layer were doing, revealing details of their behavior that had not been seen before.

Pseudogap theory puts physicists closer to high temperature superconductors

Pseudogap theory puts physicists closer to high temperature superconductors: The theory explains the transition phase to superconductivity, or "pseudogap" phase, which is one of the last obstacles to developing the next generation of superconductors and one of the major unsolved problems of theoretical condensed matter physics...

This new study found that YBa2Cu3O6+x oscillates between two quantum states during the pseudogap, one of which involves charge-density wave fluctuations. These periodic fluctuations in the distribution of the electrical charges are what destabilize the superconducting state above the critical temperature.

Scientists open a new window into quantum physics with superconductivity in LEDs

Scientists open a new window into quantum physics with superconductivity in LEDs: When a layer of such superconducting material is placed in close contact with a semiconductor LED structure, Cooper pairs are injected in to the LED, so that pairs of entangled electrons create entangled pairs of photons. The effect, however, turns out to work only in LEDs which use nanometre-thick active regions – quantum wells.

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.

Superconductivity in orbit: Scientists find new path to loss-free electricity

Superconductivity in orbit: Scientists find new path to loss-free electricity: "For the first time, we obtained direct experimental evidence of the subtle changes in electron orbitals by comparing an unaltered, non-superconducting material with its doped, superconducting twin," said Brookhaven Lab physicist and project leader Yimei Zhu...

The Brookhaven researchers used a technique called quantitative convergent beam electron diffraction (CBED) to reveal the orbital clouds with subatomic precision...

The researchers first examined the electron clouds of non-superconducting samples of barium iron arsenic. The CBED data revealed that the arsenic atoms—placed above and below the iron in a sandwich-like shape (see image)—exhibited little shift or polarization of valence electrons. However, when the scientists transformed the compound into a superconductor by doping it with cobalt, the electron distribution radically changed.

A new topological insulator breaks symmetry, and that's a good thing

A new topological insulator breaks symmetry, and that's a good thing: Most topological insulators operate as either a p-type or n-type material on both top and bottom surfaces. But BiTeCl is asymmetric: p-type on its top surface and n-type on its bottom. This means the edges of the material could function as p-n junctions – or even many microscopic p-n junctions layered on top of each other. Even better, when the material is placed in a magnetic field, these p-n junctions develop unique edge channels that can conduct electricity with zero resistance, Chen said – and this opens all sorts of possibilities.

Moreover, this unique type of material can demonstrate many other phenomena. For instance, placing it in a static electric field can induce useful magnetic properties in the material, a phenomenon known as the topological magneto-electric effect, first predicted by theorist Shoucheng Zhang of the Stanford Institute for Materials and Energy Sciences and his group. You could even use an electric charge to induce magnetic monopoles – theorized magnets that have just one pole, north or south, rather than the usual two – and then use this exotic magnetic state to do practical work, such as storing information on a hard drive, Chen said. "This is very bizarre," he said, "because people have never found magnetic monopoles as fundamental particles."

A grand unified theory of exotic superconductivity?

A grand unified theory of exotic superconductivity?: In the current paper, Davis and Lee propose and demonstrate within a simple model that antiferromagnetic electron interactions can drive both superconductivity and the various intertwined phases across different families of high-Tc superconductors. These intertwined phases and the emergence of superconductivity, they say, can be explained by how the antiferromagnetic influence interacts with another variable in their theoretical description, namely the "Fermi surface topology..."


"The basic assumption of our theory is that when we rip away all the complicated intertwined phases, underneath there is an ordinary metal," said Lee. "It is the antiferromagnetic interactions in this metal that make the electrons want to form the various states. The complex behavior originates from the system fluctuating from one state to another, e.g., from superconductor to charge density waves to nematic order. It is the antiferromagnetic interaction acting on the underlying simple metal that causes all the complexity."

First fully computer-designed superconductor | KurzweilAI

First fully computer-designed superconductor | KurzweilAI: Several years ago, Kolmogorov, then at Oxford University, began studying boron-based materials, which have complex structures and a wide range of applications. He developed an automated computational tool to identify previously unknown stable crystal structures. His “evolutionary” algorithm emulates nature, meaning it favors more stable materials among thousands of possibilities.

The search revealed two promising compounds in a common iron-boron system, which came as a surprise. Moreover, a graduate student’s calculations indicated that one of them should be a superconductor at an unusually high temperature of 15–20 Kelvin for the “conventional” type of superconductivity.

World's First Quantum Metamaterial Unveiled | MIT Technology Review

World's First Quantum Metamaterial Unveiled | MIT Technology Review: the split-ring resonators introduced losses because of their internal resistance...

a solution to this problem: use superconducting resonators...

The problem in the past is that physicists had arranged the circuits in series so that the combined state must be a superposition of the states of all the circuits. So if a single circuit was out of kilter, the entire experiment failed.

Macha and co got around this by embedding the quantum circuits inside a microwave resonator–a chamber about a wavelength long in which the microwaves become trapped.

To interact with a photon, each quantum circuit need only couple with the resonator itself and its nearest neighbours.

Teleportation with engineered quantum systems

Teleportation with engineered quantum systems: "For the first time, the stunning process of quantum teleportation has now been used in a circuit to relay information from one corner of the sample to the other.
"What makes our work interesting is the system uses a circuit, much like modern computer chips.
"In our system the quantum information is stored in artificial structures called quantum bits, and you can even see them with your bare eyes...

This research indicates that questions relating to the physics of quantum communication can be addressed using electronic circuits at microwave frequencies.

Can matter cycle through shapes eternally? : Nature News & Comment

Can matter cycle through shapes eternally? : Nature News & Comment: Wilczek's latest paper outlines another, perhaps simpler, scheme for making a time crystal. It starts with two chunks of superconductor connected by a nonsuperconductor. This device,called a Josephson junction, can create fluctuations in currents if an external voltage is applied. Wilczek argues that merely breaking the contact between the superconductors could create the type of fluctuations that characterize a time crystal.

New evidence to aid search for charge 'stripes' in superconductors

New evidence to aid search for charge 'stripes' in superconductors: ...uncovering the detailed relationship between these stripe patterns and the appearance or disappearance of superconductivity is extremely difficult, particularly because the stripes that may accompany superconductivity are very likely moving, or fluctuating.


The scientists ground up crystals of the test material into a fine powder and placed samples of it in line with a beam of neutrons...


With increasing temperature, the scientists found that while the aspect ratio of the crystal structure changed, the displacements from average structure persisted, leading them to conclude by inference that the striped pattern of charge density also remained, even though it was no longer static.

"This is the first powder diffraction scattering evidence for fluctuating charge stripes above the temperature where we see static order..."

Team finds new way to use X-rays to probe properties of solid materials

Team finds new way to use X-rays to probe properties of solid materials: The energy and power density of incoming laser light can get so high that photons actually work together and nonlinear effects result from their interaction with matter. This results in materials greatly enhancing certain colors of light. In other words, if you irradiate a crystal with green light, the light that gets irradiated is actually red. This color can be precisely correlated with the structural properties of the material that is being analyzed.
Now, Alexander F�hlisch from the HZB and his team were able to observe through a series of experiments at Hamburg's short-pulse X-ray laser FLASH that these types of effects can also be achieved using soft X-rays and that this method works on solids as well. "Normally, inelastic scattering processes using soft X-rays are ineffective," explains Martin Beye, the study's primary author: "Our experiment allowed us to document how inelastic X-ray scattering can be intelligently intensified. Just like a laser, the different photons are actually working together and amplifying each other and we end up with a very high measurement signal."

ORNL superconducting wire yields unprecedented performance

ORNL superconducting wire yields unprecedented performance: A team led by ORNL's Amit Goyal demonstrated that superconducting wires can be tuned to match different operating conditions by introducing small amounts of non-superconducting material that influences how the overall material behaves...

A wire sample grown with this process exhibited unprecedented performance in terms of engineering critical current density...

"We report a record performance at 65 Kelvin and 3 Tesla, where most rotating machinery applications like motors and generators are slated to operate," he said.

"When you're making the wires, you can dial-in the properties because the defects self-assemble," Goyal said. "You change the composition of the superconductor when you're depositing the tape."