ikenbot:

Quantum Entanglement With the Past

Side Note: Remember when I was going off on my ramblings about using quantum entanglement to somehow communicate with the past? Well this may not be as imaginative and hopeful about communicating with the past in our dimension as opposed to that of the quantum world but here’s an awesome article from livescience getting into this recent experiment physicists did back in April of this year, 2012. Basically they showed that in theory, it is possible to send a particle from one computer into another across vast distances long after one particle has ceased to exist, showing that quantum entanglement works both ways. A particle in the future can alter one in the past. This kind of experiment and discovery is paramount to the future of how we use our communications technology.

Entanglement is a weird state where two particles remain intimately connected, even when separated over vast distances, like two die that must always show the same numbers when rolled. For the first time, scientists have entangled particles after they’ve been measured and may no longer even exist.

If that sounds baffling, even the researchers agree it’s a bit “radical,” in a paper reporting the experiment published online April 22 in the journal Nature Physics.

“Whether these two particles are entangled or separable has been decided after they have been measured,” write the researchers, led by Xiao-song Ma of the Institute for Quantum Optics and Quantum Information at the University of Vienna.

Essentially, the scientists showed that future actions may influence past events, at least when it comes to the messy, mind-bending world of quantum physics.

In the quantum world, things behave differently than they do in the real, macroscopic worldwe can see and touch around us. In fact, when quantum entanglement was first predicted by the theory of quantum mechanics, Albert Einstein expressed his distaste for the idea, calling it “spooky action at a distance.”

The researchers, taking entanglement a step further than ever before, started with two sets of light particles, called photons.

The basic setup goes like this:

Both pairs of photons are entangled, so that the two particles in the first set are entangled with each other, and the two particles in the second set are entangled with each other. Then, one photon from each pair is sent to a person named Victor. Of the two particles that are left behind, one goes to Bob, and the other goes to Alice.

But now, Victor has control over Alice and Bob’s particles. If he decides to entangle the two photons he has, then Alice and Bob’s photons, each entangled with one of Victor’s, also become entangled with each other. And Victor can choose to take this action at any time, even after Bob and Alice may have measured, changed or destroyed their photons.

“The fantastic new thing is that this decision to entangle two photons can be done at a much later time,” said research co-author Anton Zeilinger, also of the University of Vienna. “They may no longer exist.”

Such an experiment had first been predicted by physicist Asher Peres in 2000, but had not been realized until now.

“The way you entangle them is to send them onto a half-silvered mirror,” Zeilinger told LiveScience. “It reflects half of the photons, and transmits half. If you send two photons, one to the right and one to the left, then each of the two photons have forgotten where they come from. They lose their identities and become entangled.”

Zeilinger said the technique could one day be used to communicate between superfast quantum computers, which rely on entanglement to store information. Such a machine has not yet been created, but experiments like this are a step toward that goal, the researchers say.

“The idea is to create two particle pairs, send one to one computer, the other to another,” Zeilinger said.”Then if these two photons are entangled, the computers could use them to exchange information.”

christinetheastrophysicist:

ALICE scientists probe what happens to matter heated to 250,000 times temperature at sun’s center

Scientists at CERN have smashed together various particles for the first time, moving closer to learning what was in the super-hot plasma wonderland that formed right after the primeval Big Bang, the European physics research center said on Thursday.

Read More.

quantumaniac:

Physicists Explain the Collective Motion of Fermions

Some people like company. Others prefer to be alone. The same holds true for the particles that constitute the matter around us: Some, called bosons, like to act in unison with others. Others, called fermions, have a mind of their own.

Different as they are, both species can show “collective” behaviour — an effect similar to the wave at a baseball game, where all spectators carry out the same motion regardless of whether they like each other.

Scientists generally believed that such collective behavior, while commonplace for bosons, only appeared in fermions moving in unison at very long wavelengths. Now, however, collective behavior has been discovered at short wavelengths in one Fermi system, helium-3.

A team led by Professor Eckhard Krotscheck — a physicist who recently joined the University at Buffalo from the Johannes Kepler University in Linz, Austria — predicted the existence of the behaviour using theoretical tools. Independently, but practically at the same time, a French team observed the collective behaviour.

“Knowing how nature ticks at a microscopic scale, we set out to develop a robust theory that was capable of dealing with a wide range of situations and systems,” Krotscheck said. “We demanded that our mathematical description is accurate for both fermions and bosons, in different dimensions, and for both coherent and incoherent excitations. Only after we were done, we looked at experiments.”

cwnl:

Neutrinos: Everything You Need To Know

What exactly are they?

With a neutral charge and nearly zero mass, neutrinos are the shadiest of particles, rarely interacting with ordinary matter and slipping through our bodies, buildings and the Earth at a rate of trillions per second.

First predicted in 1930 by Wolfgang Pauli, who won a Nobel prize for this work in 1945, they are produced in various nuclear reactions: fusion, which powers the sun; fission, harnessed by humans to make weapons and energy; and during natural radioactive decay inside the Earth.

If they are so stealthy, how do we know they are there at all?

Wily neutrinos usually avoid contact with matter, but every so often, they crash into an atom to produce a signal that allows us to observe them. Fredrick Reines first detected them in 1956, garnering himself a Nobel prize in 1995.

Most commonly, experiments use large pools of water or oil. When neutrinos interact with electrons or nuclei of those water or oil molecules, they give off a flash of light that sensors can detect.

Where are these experiments found?

These days, a lot of expense and extreme engineering go into detectors that are sunk into the ground to shield them from extraneous particles that might interfere with them. For instance, OPERA, which detected the apparently faster-than-light neutrinos beamed from CERN, lies inside the Gran Sasso mountain in Italy. This works because neutrinos shoot straight through such shields.

Other detectors pick up naturally-produced neutrinos. One such detector – ANTARES – is miles under the Mediterranean Sea, while another, IceCube, is buried under Antarctic ice.

What’s cool about neutrinos?

Their stealth belies their potential importance. Take extra dimensions. Most particles come in two varieties: ones that spin clockwise and ones that spin anticlockwise. Neutrinos are the only particles that seem to just spin anticlockwise. Some theorists say this is evidence for extra dimensions, which could host the “missing”, right-handed neutrinos.

Anything else?

Unseen right-handed neutrinos may also account for mysterious dark matter. This is thought to make up 80 per cent of all matter in the universe and to stop galaxies from flying apart. The idea is that right-handed neutrinos might be much heavier than left-handed ones and so could provide the requisite gravity.

For More on Neutrinos, Read More Here

The beautiful subatomic world, as gracious and spacious as the cosmos.