Wednesday, January 29, 2014

Magnetic poles can 'split in two'


If you break a magnet in two, you don't get a north half and a south half - you get two new magnets, each with two poles.


'Monopoles' were famously predicted to exist by physicist Paul Dirac in 1931 - but they have remained elusive.


Now scientists have engineered a synthetic monopole in a quantum system for the first time, allowing its mysterious properties to be explored.


They describe their breakthrough in Nature journal.


'Detecting a natural magnetic monopole would be a revolutionary event comparable to the discovery of the electron,' wrote the team from Aalto University, Finland, and Amherst College, US, in their paper.


'[Our work] provides conclusive and long-awaited experimental evidence of the existence of Dirac monopoles.


'It provides an unprecedented opportunity to observe and manipulate these quantum mechanical entities in a controlled environment.'


The discovery of magnetic monopoles has been long-awaited as they can help to explain various physical phenomena.


Researchers have hunted for them since Paul Dirac first theorised their quantum-mechanical characteristics in 1931.


He demonstrated that if even a single monopole exists, then all electrical charge must come in discrete packets - which has indeed been demonstrated.


To observe and test them in the lab, scientists engineered a quantum system - the magnetic field of a cloud of rubidium atoms in an unusual state of matter known as a Bose-Einstein condensate.


Using direct imaging, they detected a distinct signature of the Dirac monopole - known as a ' Dirac string'.


The researchers note that - while other teams have previously made analogues of monopoles, their demonstration is the first in a quantum system which can be tested by experiment.


'This creation of a Dirac monopole is a beautiful demonstration of quantum simulation,' said Lindsay LeBlanc, of the University of Alberta, a physicist not involved in the study.


'Although these results offer only an analogy to a magnetic monopole, their compatibility with theory reinforces the expectation that this particle will be detected experimentally.


'As Dirac said in 1931: 'Under these circumstances one would be surprised if Nature had made no use of it'.'