Author: Michael Brooks

IF YOU thought that quantum entanglement- the weird effect that allows two particles to behave as one, no matter how far apart they are- is too subtle to affect your daily life, think again. The phenomenon could be responsible for something as significant as the mass of everyday objects, yourself included, and could finally explain why the fundamental particles of matter have the mass they do.

Sometimes, the interaction of two particles, say electrons, causes their individual properties, such as spin, to become "entangled". If you then change the spin of one particle it will instantly affect the spin of the other, regardless of the distance between them.

There is mounting evidence that entanglement has consequences in the macroscopic world. Last year physicist Vlatko Vedral of the University of Leeds, UK, showed that entanglement is involved in superconductivity. Now, he has shown in a paper submitted to the journal Physical Review Letters that entanglement can explain one of the defining traits of superconductivity- the Meissner effect, in which a magnet will levitate above a piece of superconducting material. The magnetic field induces a current in the surface of the superconductor, and this current effectively excludes the magnetic field from the interior of the material, causing the magnet to hover.

Only a current composed of entangled electrons in the superconductor can achieve this effect, Vedral says. The current halts the photons of the magnetic field after they have travelled only a short distance through the superconductor. For the normally massless photons it is as if they have suddenly entered treacle, effectively giving them a mass.

Vedral also claims that a similar mechanism may be behind the mass of all particles. The standard model of physics says that matter is made of particles such as electrons, neutrinos, and quarks, while the various forces in the universe, such as the strong and weak nuclear forces, act through "mediator" particles such as the gluon. In theory, these mediators are all massless, and so all the fundamental forces should act over infinite distances. In reality, they don't: the forces have a limited range, and the mediator particles have mass.

Physicists believe that the source of this mass is something called the Higgs field that fills the universe and is mediated by a particle known as the Higgs boson. These bosons are thought to exist in a "condensed" state that excludes the mediator particles such as gluons in the same way that a superconductor's entangled electrons exclude the photons of a magnetic field. This exclusion by the Higgs field is what gives the mediator particles an effective mass, and also limits their range of influence. But no one has yet seen a Higgs boson, let alone shown exactly how they exclude, say, gluons.

Entanglement could be the answer. Vedral has shown that the condensation of the Higgs bosons and exclusion of the mediators requires entanglement between the Higgs bosons. Entanglement may be linked to the mass of not just the mediator particles, but all fundamental particles. Different particles would interact differently with the entangled Higgs bosons, providing different "effective masses" for each particle.
Vedral admits that the idea is still sketchy. "Intuitively speaking, I think there must be a connection [between entanglement and mass]," he says. "But whether we can quantify it is still unclear."

Other physicists contacted by New Scientist are reserving judgement until there is a more concrete footing for the numbers involved. Jens Eisert, of the University of Potsdam in Germany, agrees with Vedral that the idea is still too sketchy. But more work might expose something worth pursuing, he says. "The connection [of entanglement] to the Higgs field, if it could be substantiated by a quantitative argument, is clearly intriguing."

SOURCE : http://www.newscientist.com