Uncertainty Principle Taken to Its Limits

Uncertainty Principle

It has been a good couple of weeks for Heisenberg and physics in general. Two new papers have been published recently addressing one of the fundamental principles of quantum mechanics, showing that the Uncertainty Principle can be taken to limits not known to be previously possible. This principle, originally described by Werner Heisenberg in 1927, was formally proven last month, while a new study shows that this principle can be “tricked” such that physicists can gain better, more accurate measurements of the behavior of objects in motion.

The Uncertainty Principle, sometimes referred to as the Principle of Indeterminacy, was nicely summed up by Heisenberg when he said, “The more precisely the position is determined, the less precisely the momentum is known in this instant, and vice versa.” While arguing with Schrodinger, who postulated the infamous “Schrodinger’s Cat” experiment, Heisenberg found that when trying to measure both the position and the momentum of a particle at the same time, there were always going to be imprecisions – or uncertainties – in the results.

Although widely accepted and used in theoretical and quantum physics, the Uncertainty Principle lacked a thorough and definitive proof. Last month, however, an important paper was published that offers such a proof. Published in the Journal of Mathematical Physics,  the paper not only shows the proof of this principle, but also explores how measurement of accuracy would differ based on the instrumentation used to measure the behavior of the particle of interest, giving mathematical proof that the limits to the Uncertainty Principle could be taken farther than previously thought.

That is where the newest study comes in. Published earlier this week in Science, one of the preeminent scientific journals in the world, the research team led by Keith Schwab at CalTech showed how they were able to reduce the uncertainty, or noise, that is amplified when one tries to get better and better signal measurements of an object in motion. Schwab explained that “…if you shine light at an object, the photons that scatter off provide information about the object. But the photons don’t all hit and scatter at the same time, and the random pattern of scattering creates quantum fluctuations.” Furthermore, merely shining more light does not enhance the picture: even as the signal improves, the noise increases.

In order to reduce this noise, Schwab’s team developed an aluminum device about the width of a strand of hair. This device was designed to capture the quantum noise produced by the microwaves, which have a longer wavelength than visible light waves. This quantum noise could be measured by detecting the shaking of mechanical plates within the device. Researchers were then able to adjust their equipment and mathematical approach to reduce this noise in order to enhance measurement of the microwaves.

Given the relatively large size of these microwaves in comparison to protons and electrons, the scientists hope that one day, physicists may be able to extend this research to even larger objects, and see if they can behave in quantum ways – including superposition and entanglement – like particles do. The key question is whether it is possible to make a larger object exist in two places at the same time.

It is too early to say, as physicists simply do not know where the boundary of quantum mechanics lies with respect to objects of increasing size. However, with more proofs and research showing that the boundaries of this fundamental idea may actually be rather pliable, it is certain that further work will seek to explore just where the limits of the Uncertainty Principle actually lie.

By Bryan A. Jones

Nanotechnology Now
Journal of Mathematical Physics

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