Published in Physics World, 11 Mar 2013
Physicists in Canada and the US claim to be the first to make a direct measurement of the polarization quantum state of light – a feat that at first glance appears to defy Heisenberg’s uncertainty principle. The technique, which relies on a process known as weak measurement, could help in fundamental studies on quantum mechanics or in the development of quantum computing.
In quantum mechanics, it is normally considered impossible to know everything about a system at one time. Measure the position of a particle accurately, for instance, and the particle’s momentum will suddenly become very ill defined. Physicists call pairs of variables such as position and momentum “conjugate”: they are innately connected, such that the measurement of one essentially destroys information about the other. […]
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