'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.”

First Evidence Of A Correction To The Speed of Light — The Physics arXiv Blog — Medium

First Evidence Of A Correction To The Speed of Light — The Physics arXiv Blog — Medium: Because all previous speed-of-light calculations have relied only on general relativity, they do not take into account the tiny effects of quantum mechanics. But these effects are significant over such long distances and through such a large mass as the Milky Way, says Franson...

Franson’s idea is that the gravitational potential must influence the electron-positron pair because they have mass. “Roughly speaking, the gravitational potential changes the energy of a virtual electron-positron pair, which in turn produces a small change in the energy of a photon,” he says. “This results in a small correction to the angular frequency of a photon and thus its velocity.”

If Spacetime Were a Superfluid, Would It Unify Physics—or Is the Theory All Wet? - Scientific American

If Spacetime Were a Superfluid, Would It Unify Physics—or Is the Theory All Wet? - Scientific American: If it is true that spacetime is a superfluid and that photons of different energies travel at different speeds or dissipate over time, that means relativity does not hold in all situations. One of the main tenets of relativity, the Lorentz invariance, states that the speed of light is unchanging, regardless of an observer’s frame of reference. “The possibility that spacetime as we know it emerges from something that violates relativity is a fairly radical one,” Jacobson says. It does, however, clear a potential pathway toward rectifying some of the problems that arise when trying to combine relativity and quantum mechanics. “Violating relativity would open up the possibility of eliminating infinite quantities that arise in present theory and which seem to some unlikely to be physically correct.”

Scientists discover how to turn light into matter after 80-year quest

Scientists discover how to turn light into matter after 80-year quest: The collider experiment that the scientists have proposed involves two key steps. First, the scientists would use an extremely powerful high-intensity laser to speed up electrons to just below the speed of light. They would then fire these electrons into a slab of gold to create a beam of photons a billion times more energetic than visible light.
The next stage of the experiment involves a tiny gold can called a hohlraum (German for 'empty room'). Scientists would fire a high-energy laser at the inner surface of this gold can, to create a thermal radiation field, generating light similar to the light emitted by stars.
They would then direct the photon beam from the first stage of the experiment through the centre of the can, causing the photons from the two sources to collide and form electrons and positrons. It would then be possible to detect the formation of the electrons and positrons when they exited the can.

Quantum Random Number Generator Created Using A Smartphone Camera� — The Physics arXiv Blog — Medium

Quantum Random Number Generator Created Using A Smartphone Camera� — The Physics arXiv Blog — Medium:  It’s straightforward to calculate the average number of electrons this process should produce, given the probabilistic nature of photon emission. But the actual number of electrons should differ by a number that is random. That produces a single random digit. And since a light-sensitive array consists of many pixels working in parallel, it is possible to generate a large quantity of random digits from each image...

So the process of generating random numbers consists of pointing the camera at a green LED that evenly illuminates all the pixels and pressing the shutter button. A simple program then extracts the random digits.

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.

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..."

Mobius strip ties liquid crystal in knots to produce tomorrow's materials and photonic devices

Mobius strip ties liquid crystal in knots to produce tomorrow's materials and photonic devices
...they simulated adding a micron sized silica particle – or colloid – to the liquid crystal. This disrupts the orientation of the liquid crystal molecules.

For example, a colloid in the shape of a sphere will cause the liquid crystal molecules to align perpendicular to the surface of the sphere, a bit like a hedgehog's spikes.
Using a theoretical model, the University of Warwick scientists have taken this principle and extended it to colloids which have a knotted shape in the form a Möbius strip...


By adding these specially designed knotted particles they force the liquid crystal to take on the same structure, creating a knot in the liquid crystal...
"Recently it has been demonstrated that knots can be created in a variety of natural settings including electromagnetic fields, laser light, fluid vortices and liquid crystals.

Quantum teleportation approaches the computer chip | Matter & Energy | Science News

Quantum teleportation approaches the computer chip | Matter & Energy | Science News; Now physicist Andreas Wallraff at ETH Zurich and his team have created the first solid-state device, similar to a computer chip, that is capable of teleporting quantum information. The chip contains tiny circuits that each behave like an atom. The circuits are connected by millimeters-long transmission lines carrying microwave radiation, which entangles the circuits so that the properties of one affect the other. By programming a bit of quantum information into circuit A, Wallraff and his team changed the signal arriving at circuit B. They could then use that changed signal to determine the original properties of circuit A and transfer them to circuit B.

Most importantly, Wallraff’s teleportation system successfully transports information in nearly every attempt, and it can do it roughly 10,000 times per second, an unprecedented rate.

When fluid dynamics mimic quantum mechanics | KurzweilAI

When fluid dynamics mimic quantum mechanics | KurzweilAI: In the experiments reported in PRE, the researchers mounted a shallow tray with a circular depression in it on a vibrating stand. They filled the tray with a silicone oil and began vibrating it at a rate just below that required to produce surface waves.

They then dropped a single droplet of the same oil into the bath. The droplet bounced up and down, producing waves that pushed it along the surface.

The waves generated by the bouncing droplet reflected off the corral walls, confining the droplet within the circle and interfering with each other to create complicated patterns. As the droplet bounced off the waves, its motion appeared to be entirely random, but over time, it proved to favor certain regions of the bath over others...

The statistical description of the droplet’s location is analogous to that of an electron confined to a circular quantum corral and has a similar, wavelike form.

What if quantum entanglement worked on the macroscopic level? | KurzweilAI

What if quantum entanglement worked on the macroscopic level? | KurzweilAI: ...now they have entangled two optic fibers, populated by 500 photons.

To do this, the team first created an entanglement between two fiber optics on a microscopic level before moving it to the macroscopic level. The entangled state survived the transition to a larger-scale world and the phenomenon could even be observed with the naked eye...

Physicists Create Quantum Link Between Photons That Don't Exist at the Same Time

Physicists Create Quantum Link Between Photons That Don't Exist at the Same Time: They start with a scheme known as entanglement swapping. To begin, researchers zap a special crystal with laser light a couple of times to create two entangled pairs of photons, pair 1 and 2 and pair 3 and 4. At the start, photons 1 and 4 are not tangled. But they can be if physicists play the right trick with 2 and 3.

The key is that a measurement "projects" a particle into a definite state -- just as the measurement of a photon collapses it into either vertical or horizontal polarization. So even though photons 2 and 3 start out unentangled, physicists can set up a "projective measurement" that asks, are the two in one of two distinct entangled states or the other? That measurement entangles the photons, even as it absorbs and destroys them. If the researchers select only the events in which photons 2 and 3 end up in, say, the first entangled state, then the measurement also entangles photons 1 and 4. (See diagram, top.) The effect is a bit like joining two pairs of gears to form a four-gear chain: Enmeshing to inner two gears establishes a link between the outer two.

In recent years, physicists have played with the timing in the scheme. For example, last year a team showed that entanglement swapping still works even if they make the projective measurement after they've already measured the polarizations of photons 1 and 4. Now, Eisenberg and colleagues have shown that photons 1 and 4 don't even have to exist at the same time, as they report in a paper in press at Physical Review Letters.

To do that, they first create entangled pair 1 and 2 and measure the polarization of 1 right away. Only after that do they create entangled pair 3 and 4 and perform the key projective measurement. Finally, they measure the polarization of photon 4. And even though photons 1 and 4 never coexist, the measurements show that their polarizations still end up entangled. Eisenberg emphasizes that even though in relativity, time measured differently by observers traveling at different speeds, no observer would ever see the two photons as coexisting.

Physicists make discovery in the quantum realm by manipulating light

Physicists make discovery in the quantum realm by manipulating light: "In our experiment, we caught and released photons in and from a superconducting cavity by incorporating a superconducting switch," said Yin. "By controlling the switch on and off, we were able to open and close a door between the confined cavity and the road where photons can transmit. The on/off speed should be fast enough with a tuning time much shorter than the photon lifetime of the cavity." She explained that not only can the switch be in an on/off state, it also can be opened continuously, like a shutter. In that way, the research team was able to shape the released photons in different wave forms –– a key element for the next step they want to accomplish: controlled photon transfer between two distant cavities.

How to Measure Quantum Foam With a Tabletop Experiment

How to Measure Quantum Foam With a Tabletop Experiment: Bekenstein's goal is to move the block by a distance that is about equal to the Planck length. His method is simple: zap the block with a single photon.

The photon carries a small amount of moment and consequently pushes the block as it enters the glass, giving it some momentum.  As the photon leaves the block, the block comes to rest.

So the result of the photon's passage is that it moves the block a small distance.

Bekenstein's idea is that if this distance is smaller than the Planck length, then the block cannot move and the photon cannot pass through it.

So the experiment involves measuring the number of photons that pass through the block. If the number is fewer than predicted by classical optics, then that proves the existence of quantum foam.

Higgs boson continues to be maddeningly well-behaved

Higgs boson continues to be maddeningly well-behaved: Today, experimentalists from CMS and the other main LHC detector ATLAS, armed with twice as much data as they had in July, told the Hadron Collider Physics symposium in Kyoto, Japan, that the number of tau particles detected has crept up. The new data can't yet rule out a deviation from the standard model but they do remove the main reason for thinking there was one in the first place...
...direct searches for new physics at the LHC have turned up empty too. Physicists presented searches for dozens of particles that would exist in a world governed by some of these new theories...
"The results really tell us that we're either not looking in the right place, or we're not looking in the right way, or maybe both..."

Tractor beam built from rings of laser light - New Scientist - New Scientist

Tractor beam built from rings of laser light: David Ruffner and David Grier of New York University instead projected two Bessel beams side by side and used a lens to angle them so that they overlapped, creating a pattern of alternating bright and dark regions along the length of the beam. Fine-tuning the beam causes photons in the bright regions, initially flowing past a chosen particle in the beam, to scatter backwards. When these photons hit the particle, they knock it to the next bright region. The particle is thus constantly pushed close to the beam's source.

Topology: The Secret Ingredient In The Latest Theory of Everything

Topology: The Secret Ingredient In The Latest Theory of Everything: Today, Wen combines topology, symmetry and quantum mechanics in a new theory that predicts the existence of new states of matter, unifies various puzzling phenomena in solid state physics and allows the creation artificial vacuums populated with artificial photons and electrons...

Xiao-Gang Wen's approach is to explore the properties of matter when the topological links between particles become much more general and complex. He generalises these links, thinking of them as strings that can connect many  particles together. In fact, he considers the way many strings can form net-like structures that have their own emergent properties...
That makes string nets a kind of "quantum ether" through which electromagnetic waves travel. That's a big claim.

How To Build A Black Hole Laser - Technology Review

How To Build A Black Hole Laser - Technology Review: Their idea is to create a black hole next to a white hole so that their event horizons are separated by just a few hundred micrometres and create a small cavity. Then they show that when light is fired into this cavity, it is reflected off the white hole horizon onto the black hole horizon, back to the white again and so on...
Their real triumph, however, is in showing how such a device could be made in the lab...
...a very intense beam can create a huge gradient in the refractive index. This gradient can be so steep that it behaves like an event horizon. In fact, a single pulse can create black hole horizon at its leading edge and a white hole horizon at its trailing edge.

Heavy photons are too light to be behind dark matter

Heavy photons are too light to be behind dark matter: Some theories had hinted that "heavy photons", hypothetical versions of the more familiar massless particles, might be dark matter. According to that idea, the heavy photon would have a small amount of mass and might carry an unknown fundamental force that allows it to interact only with ordinary photons...
... a photon with a very tiny "in between" mass can enter into an orbit of the spinning black hole and steal some of its angular momentum...
Cardoso and colleagues calculated how long photons of given masses would take to sap a black hole's spin. Then they examined data on the ages and rotation speeds of eight supermassive black holes. The age of the oldest spinning black holes effectively puts an upper limit on the photon's mass. If it does exist, the heavy photon must be lighter than 10-20 electronvolts - an extreme improbability...

Silicon chip enables mass-manufacture of quantum technologies

Silicon chip enables mass-manufacture of quantum technologies: Scientists from the University of Bristol’s Centre for Quantum Photonics have developed a silicon chip that may pave the way to the mass-manufacture of miniature quantum chips...
“Using silicon to manipulate light, we have made circuits over 1000 times smaller than current glass-based technologies..."