Strangest things about quantum physics may stem from overconfidence

Quantum phenomena even Einstein called 'spooky' may stem from overconfidence in what can be known about things one-millionth the size of an atom. Uncertainty, apparently, rules.

A particle may be a wave, or you may simply underestimate how little you know about where it is.
Credit: Timothy Yeo / CQT, National University of Singapore

A breakthrough that got credit for "simplifying" quantum physics could wipe away some of its more troubling contradictions by pointing out that even those who can calculate it precisely don't always get what "uncertainty" means.

A group of researchers at the National University of Singapore has suggested that the tendency of some particles to act like matter in public and like waves of energy when no one's looking may be a problem in the way physicists study particles, not the way particles behave.

The phenomenon, described as wave-particle duality is less likely to excessively creative behavior from the particle than to be the result of our failure to understand the real impact of the uncertainty principle that define the limits of how much it is possible to know about a particle, according to a study published Dec. 19 in the journal Nature Communications.

The uncertainty principle was developed in the 1920s by Werner Heisenberg, who found it is possible to know the location of a quantum particle, or the speed and direction in which it is travelling, but not both.

Since the uncertainty principle suggests we can't see all the characteristics of a particle at one time, every time we look at a quantum particle we must be seeing only a subset of the things about it we would like to see. If the list of characteristics we can see changes more than we realize,we may see particles doing things that are impossible simply because we haven't realized the information we see about it has changed from one observation to the next -- like watching a video of a person walking down the street recorded with a camera that switches from normal vision to infrared, to black-and-white and blinks the sound on or off with no indication anything had changed.

If true, the conclusion could change much of the way we think about the nature and behavior of the particles that make up the particles that make up the parts of an atom.

The idea of a wave of energy that is also a particle, for example, comes from Albert Einstein's 1905 analysis of the puzzlingly small number of electrons streaming from an artificial light source.

An observer looking at the interference pattern caused by the collision of the expanding ripples from two pebbled tossed into a pond, would have difficulty seeing what happened to a particle being carried into that collision as a part of one wave, according to an example provided by World Science.

On the quantum level – where particles are one one-hundred-millionth the size of an atom – the particle would look like a particle to anyone looking only in stop motion, and would look more like a wave to those using full-motion video.

According to Heisenberg, it's impossible to use both at the same time.

There is a similar limit on how much can be known about the wavelike behavior of particles as well, according to the authors, who described efforts to observe it as "a sort of competition between seeing the wave behavior versus the particle-like behavior." (full-text PDF here).

Wave-particle duality is "a phenomenon which is impossible, absolutely impossible, to explain in any classical way, and which has in it the heart of quantum mechanics. In reality, it contains the only mystery [in quantum mechanics,]" according to Richard Feynman, Nobel-prize-winning theoretical physicist, quantum mechanic and originator of the concept of nanotechnology, whom the authors quote in their introduction to the Dec. 19 paper.

The authors have found similar connections between uncertainty and other fundamental quantum-mechanical phenomena, including quantum entanglement – the apparent ability of two particles to communicate across vast distances with no time delay, which Einstein described as "spooky action at a distance."

If the connection is real and the authors' conclusions are accurate, it could resolve much of the perversely counterintuitive behavior that makes quantum mechanics bizarre as well as simply complicated. It could also point the way toward explanations about the behavior of the universe that don't assume the smallest, most fundamental bits of it behave in ways completely inconsistent with all the rest.

"Simplify" might not be the right description for physics based on a wider application of uncertainty, however.

It might not explain the discovery this week of what researchers insist are particles that are half matter and half light energy – one popular description of wave-particle duality in photons, for example.

"Besides being a fundamental breakthrough, this opens up the possibility of making devices which take the benefits of both light and matter," including logic gates or signal processors in integrated circuits, according to Vinod Menon, the physics professor who led the research.

If wave-particle duality is an error of uncertainty, it's likely the light/matter particle is a mistake – and so would a large chunk of the research on the quantum world during the past century.

It would, however, make much more straightforward investigations into ways to trap and manipulate individual atoms for use in subatomic-scale computing devices, for example, or precise control of the flight path, or shape of individual photons to make them more useful in quantum or optical computing.

It might not explain other things, like particles that appear to move faster than light, accelerate as they lose energy, or that have no mass but can be identified by weight, as one researcher recently said may be true of neutrinos.

The most likely result is that a new perspective will eliminate one or two major anomalies and only narrow the scope of uncertainty on some of the rest. But reducing the uncertainty on a wide range of observations and calculations might have a much higher impact than nixing the idea that a particle really can go through two different holes in the same screen at the same time.

Quantum physics depends on calculations based on probability, but not the kind bookies use to set odds. In the quantum world probabilities are not the odds that something will happen or not. They're approximations of things like where a particle might be right at the moment and what it might be doing – like a box enclosing a prize that is the size of every place the prize might be.

Changing the size of that box – and the box around our assumptions about every particle in every observation or calculation of anything related to quantum mechanics – won't just change the result of a few calculations. It will shift the position or change the value of every bit of data that goes into them – a change that would ripple through everything we know about the quantum world.

In other areas of life or science it might seem useless to work for years to make your calculations a little less inaccurate.

For people looking for answers in a discipline in which even the most fundamental information is based a gross approximation of critical data we can literally not know more precisely – reducing the size of the uncertainty is a big deal.

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