Even Large Molecules Can Behave Like Waves

Even Large Molecules Can Behave Like Waves

By Shawn Radcliffe

In many ways, quantum mechanics is very strange — like particles being connected across vast distances or being able to act like both waves and particles. But at the small scales of photons, electrons and atoms, this strangeness seems oddly fitting.

However, once you get up to the macro world that we all inhabit, those strange phenomena seem like just that — strange. You wouldn’t find baseballs entangled in such a way that hitting one affects another miles away. Or see a chicken acting like both a chicken and a wave.

At some point, as you move from the micro world to the macro world, the laws (and quirks) of quantum mechanics cease to operate (or operate in different ways that we have yet to discover). So where is the dividing line between the two (seemingly) separate worlds of quantum physics and classical physics?

The answer to that is still not entirely clear. But a new experiment by researchers from the University of Vienna in Austria suggests that even relatively large molecules can fall under the sway of quantum mechanics — under the right circumstances.

The results of the new study were published September 23 in Nature Physics.

The new experiment is a souped-up version of the classic double-slit experiment, which was first conducted in the early 1800s. In this experiment, researchers found that when they aimed light waves at a barrier with two slits, the waves created an alternating light-dark interference pattern after they had passed through.

But it’s not just waves passing through slits that create this interference pattern. Individual particles of light (a.k.a. photons) do it as well, which suggests they can act as both particles and waves. Later experiments showed that electrons and single atoms can also produce a wave-like interference pattern. And one experiment achieved this with a molecule made up of 810 atoms.

Now physicists have stretched the quantum world a little closer to our macro world. They successfully ran the double-slit experiment using a synthetic molecule containing as many as 2,000 atoms — the largest to be tested to date.

A synthetic molecule was used because the experiment required a molecule that was stable and would fly in a directed beam toward the barrier with the slits. The scientists also had to use a 2-meter long interferometer, the device that is used in the double-slit experiments.

Although these synthetic molecules aren’t quite baseball-sized (or even golf ball-sized), the experiment pushes the limits of quantum mechanics even further. Future experiments may bring the quantum world even closer to our macro world.

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