One of the oddest predictions of quantum theory — that a system can’t change while you’re watching it — has been confirmed in an experiment by physicists.
A low-cost, high-speed method for printing graphene inks using a conventional roll-to-roll printing process, like that used to print newspapers and crisp packets, could open up a wide range of practical applications, including inexpensive printed electronics, intelligent packaging and disposable sensors.
Developed by researchers at the University of Cambridge in collaboration with Cambridge-based technology company Novalia, the method allows graphene and other electrically conducting materials to be added to conventional water-based inks and printed using typical commercial equipment, the first time that graphene has been used for printing on a large-scale commercial printing press at high speed.
Graphene is a two-dimensional sheet of carbon atoms, just one atom thick. Its flexibility, optical transparency and electrical conductivity make it suitable for a wide range of applications, including printed electronics. Although numerous laboratory prototypes have been demonstrated around the world, widespread commercial use of graphene is yet to be realised.
Australian scientists created a computer simulation in which quantum particles can move back in time. This might confirm the possibility of time travel on a quantum level, suggested in 1991. At the same time, the study revealed a number of effects which are considered impossible according to the standard quantum mechanics.
Using photons, physicists from the University of Queensland in Australia simulated time-traveling quantum particles. In particular, they studied the behavior of a single photon traveling back in time through a wormhole in space-time and interacting with itself. This time-traveling loop is called a closed timelike curve, i.e. a path followed by a particle which returns to its initial space-time point.
The physicists studied two possible scenarios for a time-traveling photon. In the first, the particle passes through a wormhole, moving back in time, and interacts with its older self. In the second scenario, the photon passes through normal space-time and interacts with another photon which is stuck in a closed timelike curve.
In physics there are two broad ways to look at the world. One is the classical realm of Newton and Einstein, where objects have definite form and interact in clearly determinate ways. The other is the quantum realm, where objects seem nebulous, with a strange mix of particle-like and wave-like behavior. The classical view gives us a wonderfully accurate description of everything from planets to baseballs. The quantum view is necessary to accurately describe the behavior of light and atoms. The classical world dominates on the scale of our daily lives, but nature seems to be rooted in quantum theory at its most basic level.
While both the classical and quantum approach are extremely accurate in their respective regimes, what happens in the intersection of the two regimes is still unclear. We don’t have a rigorous theory combining our classical and quantum models. We also don’t have certain key observational evidence, particularly in the nexus of quantum theory and gravity. But as quantum experiments increasingly study more massive objects and gravity experiments become increasingly sensitive, we’re approaching the point where “quantum gravity” experiments could be made. That’s the goal of a recently proposed experiment.
Continue reading “A New Experiment May Determine Whether Gravity Is Quantized” »
Nature has had billions of years to perfect photosynthesis, which directly or indirectly supports virtually all life on Earth. In that time, the process has achieved almost 100 percent efficiency in transporting the energy of sunlight from receptors to reaction centers where it can be harnessed—a performance vastly better than even the best solar cells.
One way plants achieve this efficiency is by making use of the exotic effects of quantum mechanics—effects sometimes known as “quantum weirdness.” These effects, which include the ability of a particle to exist in more than one place at a time, have now been used by engineers at MIT to achieve a significant efficiency boost in a light-harvesting system.
Surprisingly, the MIT researchers achieved this new approach to solar energy not with high-tech materials or microchips—but by using genetically engineered viruses.
After years of searching, researchers say they’ve lastlyidentified a glueball — a particle made only of nuclear force. Hypothesized to exist as part of the standard model of particle physics, glueballs have stunned researchers since the 1970s as they can only be spotted indirectly by measuring their procedure of decay. Now, a group of particle scientists in Austria say they’ve found proof for the existence of glueballs by observing the decay of a particle identified as f0(1710). Protons and neutrons — the particles that everyday matter consist of — are made of tiny elementary particles called quarks, and quarks are seized together by even minor particles called gluons.
Researchers at Chalmers University of Technology have succeeded in an experiment where they get an artificial atom to survive ten times longer than normal by positioning the atom in front of a mirror. The findings were recently published in the journal Nature Physics.
Tl;dr: Experimentalists are bringing increasingly massive systems into quantum states. They are now close to masses where they might be able to just measure what happens to the gravitational field.
Quantum effects of gravity are weak, so weak they are widely believed to not be measurable at all. Freeman Dyson indeed is fond of saying that a theory of quantum gravity is entirely unnecessary, arguing that we could never observe its effects anyway. Theorists of course disagree, and not just because they’re being paid to figure out the very theory Dyson deems unnecessary. Measurable or not, they search for a quantized version of gravity because the existing description of nature is not merely incomplete – it is far worse, it contains internal contradictions, meaning we know it is wrong.
Take the century-old double-slit experiment, the prime example for quantum behavior. A single electron that goes through the double-slit is able to interact with itself, as if it went through both slits at once. Its behavior is like that of a wave which overlaps with itself after passing an obstacle. And yet, when you measure the electron after it went through the slit it makes a dot on a screen, like a particle would. The wave-like behavior again shows up if one measures the distribution of many electrons that passed the slit. This and many other experiments demonstrate that the electron is neither a particle nor a wave – it is described by a wave-function from which we obtain a probability distribution, a formulation that is the core of quantum mechanics.
A team of physicists has proposed a way of teleporting energy over long distances. The technique, which is purely theoretical at this point, takes advantage of the strange quantum phenomenon of entanglement where two particles share the same existence.
The researchers, who work out of Tohoku University in Japan, and led by Masahiro Hotta,describe their proposal in the latest edition of Physical Review A. Their system exploits properties of squeezed light or vacuum states that should allow for the teleportation of information about an energy state. In turn, this teleported quantum energy could be made useable.
Unlike teleportation schemes as portrayed in Star Trek or The Fly, this type of teleportation describes entanglement experiments in which two entangled particles are joined despite no apparent connection between them. When a change happens to one particle, the same change happens to the other. Hence, the impression of teleportation. Physicists have conducted experiments using light, matter, and now, energy.
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A new type of “quasiparticle” theorized by Caltech’s Gil Refael, a professor of theoretical physics and condensed matter theory, could help improve the efficiency of a wide range of photonic devices—technologies, such as optical amplifiers, solar photovoltaic cells, and even barcode scanners, which create, manipulate, or detect light.
