[extropy-chat] entanglement and mass

[Damien Broderick]

[a somewhat waffly piece perhaps of interest:]

By MICHAEL BROOKS
New Scientist

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.

Photons in treacle

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 do not: 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.