Some recent experiments out of the University of Toronto show for the first time an anomaly in measurements predicted by Werner Heisenberg’s fundamental law of quantum mechanics, the Uncertainty Principle.
Heisenberg’s uncertainty principle is an integral component of quantum physics. At the quantum scale, standard physics starts to fall apart, replaced by a fuzzy, nebulous set of phenomena. Among all the weirdness observed at this microscopic scale, Heisenberg famously observed that the position and momentum of a particle cannot be simultaneously measured, with any meaningful degree of precision. This led him to posit the uncertainty principle, the declaration that there’s only so much we can know about a quantum system, namely a particle’s momentum and position.
Now, by definition, the uncertainty principle describes a two-pronged process. First, there’s the precision of a measurement that needs to be considered, and second, the degree of uncertainty, or disturbance, that it must create. It’s this second aspect that quantum physicists refer to as the “measurement-disturbance relationship,” and it’s an area that scientists have not sufficiently explored or proven.
Up until this point, quantum physicists have been fairly confident in their ability to both predict and measure the degree of disturbances caused by a measurement. Conventional thinking is that a measurement will always cause a predictable and consistent disturbance — but as the study from Toronto suggests, this is not always the case. Not all measurements, it would seem, will cause the effect predicted by Heisenberg and the tidy equations that have followed his theory. Moreover, the resultant ambiguity is not always caused by the measurement itself.
The researchers, a team led by Lee Rozema and Aephraim Steinberg, experimentally observed a clear-cut violation of Heisenberg’s measurement-disturbance relationship. They did this by applying what they called a “weak measurement” to define a quantum system before and after it interacted with their measurement tools — not enough to disturb it, but enough to get a basic sense of a photon’s orientation.
Then, by establishing measurement deltas, and then applying stronger, more disruptive measurements, the team was able to determine that they were not disturbing the quantum system to the degree that the uncertainty principle predicted. And in fact, the disturbances were half of what would normally be expected.