Quantum Entaglement Light Photon Created to Contain Thousands of Atoms for Advanced Atomic Time Keeping

Physicists from MIT and the University of Belgrade have developed a new technique that can successfully entangle 3,000 atoms using only a single photon. The results, published today in the journal Nature, represent the largest number of particles that have ever been mutually entangled experimentally.

The researchers say the technique provides a realistic method to generate large ensembles of entangled atoms, which are key components for realizing more-precise atomic clocks.

“You can make the argument that a single photon cannot possibly change the state of 3,000 atoms, but this one photon does — it builds up correlations that you didn’t have before,” says Vladan Vuletic, the Lester Wolfe Professor in MIT’s Department of Physics, and the paper’s senior author. “We have basically opened up a new class of entangled states we can make, but there are many more new classes to be explored.”

Vuletic’s co-authors on the paper are Robert McConnell, Hao Zhang, and Jiazhong Hu of MIT, as well as Senka Cuk of the University of Belgrade.

Atomic entanglement and timekeeping

Entanglement is a curious phenomenon: As the theory goes, two or more particles may be correlated in such a way that any change to one will simultaneously change the other, no matter how far apart they may be. For instance, if one atom in an entangled pair were somehow made to spin clockwise, the other atom would instantly be known to spin counterclockwise, even though the two may be physically separated by thousands of miles.

The phenomenon of entanglement, which physicist Albert Einstein once famously dismissed as “spooky action at a distance,” is described not by the laws of classical physics, but by quantum mechanics, which explains the interactions of particles at the nanoscale. At such minuscule scales, particles such as atoms are known to behave differently from matter at the macroscale.

Scientists have been searching for ways to entangle not just pairs, but large numbers of atoms; such ensembles could be the basis for powerful quantum computers and more-precise atomic clocks. The latter is a motivation for Vuletic’s group.

Today’s best atomic clocks are based on the natural oscillations within a cloud of trapped atoms. As the atoms oscillate, they act as a pendulum, keeping steady time. A laser beam within the clock, directed through the cloud of atoms, can detect the atoms’ vibrations, which ultimately determine the length of a single second.

“Today’s clocks are really amazing,” Vuletic says. “They would be less than a minute off if they ran since the Big Bang — that’s the stability of the best clocks that exist today. We’re hoping to get even further.”

The accuracy of atomic clocks improves as more and more atoms oscillate in a cloud. Conventional atomic clocks’ precision is proportional to the square root of the number of atoms: For example, a clock with nine times more atoms would only be three times as accurate. If these same atoms were entangled, a clock’s precision could be directly proportional to the number of atoms — in this case, nine times as accurate. The larger the number of entangled particles, then, the better an atomic clock’s timekeeping.

Picking up quantum noise

Scientists have so far been able to entangle large groups of atoms, although most attempts have only generated entanglement between pairs in a group. Only one team has successfully entangled about 100 atoms — the largest mutual entanglement to date, and only a small fraction of the whole atomic ensemble.

Now Vuletic and his colleagues have successfully created a mutual entanglement among 3,000 atoms, virtually all the atoms in the ensemble, using very weak laser light — down to pulses containing a single photon. The weaker the light, the better, Vuletic says, as it is less likely to disrupt the cloud. “The system remains in a relatively clean quantum state,” he says.

Precise Time:

http://scienceblog.com/77507/thousands-of-atoms-entangled-with-a-single-photon/#AwsqjGt7EjiqpmwC.97

Quantum Chemistry Nanomedicine Theoretical and Computational Future Technologies

The absurd world of the electrons

The quantum chemical calculations solve the Schrödinger equation for molecules. This equation is fundamental to all chemistry and describes the whereabouts of all electrons within a molecule. But here we need to pay attention, for things are really rather more complicated than that. Your high school physics teacher will have told you that electrons circle the atom. Things are not that simple, though, in the world of quantum physics. Electrons are not only particles, but waves as well. The electrons can be in many places at the same time. It's impossible to keep track of their position. However, there is hope. Quantum chemical models describe the electrons' statistical positions. In other words, they can establish the probable location of each electron.

The results of a quantum chemical calculation are often more accurate than what is achievable experimentally.

Among other things, the quantum chemical calculations can be used to predict chemical reactions. This means that the chemists will no longer have to rely on guesstimates in the lab. It is also possible to use quantum chemical calculations in order to understand what happens in experiments.

Enormous calculations

The calculations are very demanding.

"The Schrödinger equation is a highly complicated, partial differential equation, which cannot be accurately solved. Instead, we need to make do with heavy simulations," says researcher Simen Kvaal.

The computations are so demanding that the scientists use one of the University's fastest supercomputers.

"We are constantly stretching the boundaries of what is possible. We are restricted by the available machine capacity," explains Helgaker.

Ten years ago it took two weeks to carry out the calculations for a molecule with 140 atoms. Now it can be done in two minutes.

"That's 20,000 times faster than ten years ago. The computation process is now running 200 times faster because the computers have been doubling their speed every eighteen months. And the process is a further 100 times faster because the software has been undergoing constant improvement," says senior engineer Simen Reine.

This year the research group has used 40 million CPU hours, of which twelve million were on the University's supercomputer, which is fitted with ten thousand parallel processors. This allows ten thousand CPU hours to be over and done with in 60 minutes.

"We will always fill the computer's free capacity. The higher the computational capacity, the bigger and more reliable the calculations."
Thanks to ever faster computers, the quantum chemists are able to study ever larger molecules.

Today, it's routine to carry out a quantum chemical calculation of what happens within a molecule of up to 400 atoms. By using simplified models it is possible to study molecules with several thousand atoms. This does, however, mean that some of the effects within the molecule are not being described in detail.
The researchers are now getting close to a level which enables them to study the quantum mechanics of living cells.

"This is exciting. The molecules of living cells may contain many hundred thousand atoms, but there is no need to describe the entire molecule using quantum mechanical principles. Consequently, we are already at a stage when we can help solve biological problems."

Hunting for the electrons of the insulin molecule

The chemists are thus able to combine sophisticated models with simpler ones. "This will always be a matter of what level of precision and detail you require. The optimal approach would have been to use the Schrödinger equation for everything."

By way of compromise they can give a detailed description of every electron in some parts of the model, while in other parts they are only looking at average numbers.

"We are always having to find a good balance between the details we need and those we don't need."

Simen Reine has been using the team's computer program, while working with Aarhus University, on a study of the insulin molecule. An insulin molecule consists of 782 atoms and 3,500 electrons.

"All electrons repel each other, while at the same time being pulled towards the atom nuclei. The atom nuclei also repel each other. Nevertheless, the molecule remains stable. In order to study a molecule to a high level of precision, we therefore need to consider how all of the electrons move relative to one another. Such calculations are referred to as correlated equations and are very reliable."
A complete correlated equation of the insulin molecule takes nearly half a million CPU hours. If they were given the opportunity to run the program on the University's supercomputer, the calculations would theoretically take two days.
"In ten years, we'll be able to make these calculations in two minutes."

Medically important

Vice Rector Knut Fægri at the University of Oslo points out that quantum chemical calculations may become important to life sciences.
"Quantum chemical calculations can help describe phenomena at a level that may be difficult to access experimentally, but may also provide support for interpreting and planning experiments. Today, the calculations will be put to best use within the fields of molecular biology and biochemistry," says Knut Fægri.
Associate Professor Michele Cascella at the Centre for Theoretical and Computational Chemistry has recently been recruited from Italy to introduce quantum chemistry into life sciences.

"Quantum chemistry is a fundamental theory which is important for explaining molecular events, which is why it is essential to our understanding of biological systems," says Michele Cascella.

By way of an example, he refers to the analysis of enzymes. Enzymes are molecular catalysts that boost the chemical reactions within our cells.
Cascella also points to nanomedicines, which are drugs tasked with distributing medicine round our bodies in a much more accurate fashion.
"In nanomedicine we need to understand physical phenomena on a nano scale, forming as correct a picture as possible of molecular phenomena. In this context, quantum chemical calculations are important," explains Michele Cascella.

Tricorder Your Way to Article:

http://www.sciencedaily.com/releases/2015/01/150129094112.htm?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+sciencedaily%2Fmatter_energy%2Fphysics+%28Physics+News+--+ScienceDaily%29

The Old Myth of Glass Get's Shattered: Is it a Liquid or a Solid? YES

Does glass ever stop flowing? Researchers at the University of Bristol and Kyoto University have combined computer simulation and information theory, originally invented for telephone communication and cryptography, to answer this puzzling question.

Watching a glass blower at work we can clearly see the liquid nature of hot glass.  Once the glass has cooled down to room temperature though, it has become solid and we can pour wine in it or make window panes out of it.

On a microscopic scale, solidification means that molecules have settled into a crystalline structure.  And yet, when looked at under the microscope, it appears glass never settles down but keeps flowing, albeit extremely slowly – so slowly, in fact, that it would take over 10 million years for a window pane to flow perceptibly.

This puzzle of a material which seems solid to any observer while appearing fluid under the microscope is an old one.  And even with the help of today's supercomputers it seems impossible to verify in simulations whether a glass ever stops flowing.

To answer the question of what happens at very low temperature, and whether the whole material becomes truly solid, researchers in Bristol’s Schools of Physics, Chemistry and Mathematics led by Dr Paddy Royall and Dr Karoline Wiesner, teamed up with Professor Ryoichi Yamamoto of Kyoto University.

The researchers discovered that the size of the solid-like regions of the material increases over time and that atoms in the solid-like regions organize into geometrical shapes, such as icosahedra.  Such icosahedral configurations were predicted in 1952 by Sir Charles Frank at the University of Bristol’s HH Wills Physics Laboratory.

Dr Karoline Wiesner said: “Information theory provided us with the mathematical tools to detect and quantify the movements of atoms, which turned out to move as if they were in communication with each other."

Dr Paddy Royall added: "We found that the size of the solid regions of icosahedra would grow until eventually there would be no more liquid regions and so the glass should be a true solid.”

The research, which was carried out as part of the Bristol-Kyoto agreement and Bristol Centre for Complexity Sciences, is published today in Nature Communications.

Source Feed:

http://www.bristol.ac.uk/news/2015/january/glass-a-true-solid.html