March 18, 2013
Weizmann Institute researchers suggest one can affect an atom´s spin by adjusting the way it is measured
One of the most basic laws of quantum mechanics is that a system can be in more than one state — it can exist in multiple realities — at once. This phenomenon, known as the superposition principle, exists only so long as the system is not observed or measured in any way. As soon as such a system is measured, its superposition collapses into a single state. Thus, we, who are constantly observing and measuring, experience the world around us as existing in a single reality.
Next, the team measured the polarization of the emitted photon and found that the observed polarization determines the effect of measurement on the spin. This suggests that an observer can influence the collapse of superposition just by adjusting the orientation of his photon-polarization measurement apparatus.
The reason for this “action-at-a-distance” is that the spins of the measured atoms and the emitted photons were entangled. That is, even after they were separated, a measurement of one of them instantaneously affected the other.
The experiment is an important step in understanding the measurement process in quantum systems.
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