Here's a nice surprise: quantum physics is less complicated than we thought. An international team of researchers has proved that two peculiar¹ features of the quantum world previously² considered distinct are different manifestations³ of the same thing. The result is published 19 December in Nature Communications. Patrick Coles, Jedrzej Kaniewski, and Stephanie Wehner made the breakthrough while at the Centre for Quantum Technologies at the National University of Singapore. They found that 'wave-particle duality' is simply the quantum 'uncertainty⁴ principle' in disguise, reducing two mysteries to one.

 

"The connection between uncertainty and wave-particle duality comes out very naturally when you consider them as questions about what information you can gain about a system. Our result highlights the power of thinking about physics from the perspective of information," says Wehner, who is now an Associate Professor at QuTech at the Delft University of Technology in the Netherlands.

 

The discovery deepens our understanding of quantum physics and could prompt ideas for new applications of wave-particle duality.

 

Wave-particle duality is the idea that a quantum object can behave like a wave, but that the wave behaviour disappears if you try to locate the object. It's most simply seen in a double slit⁵ experiment, where single particles, electrons, say, are fired one by one at a screen containing two narrow slits⁶. The particles pile up behind the slits not in two heaps as classical objects would, but in a stripy pattern like you'd expect for waves interfering⁷. At least this is what happens until you sneak⁸ a look at which slit a particle goes through -- do that and the interference pattern vanishes.

 

The quantum uncertainty principle is the idea that it's impossible to know certain pairs of things about a quantum particle at once. For example, the more precisely⁹ you know the position of an atom, the less precisely you can know the speed with which it's moving. It's a limit on the fundamental knowability of nature, not a statement on measurement skill. The new work shows that how much you can learn about the wave versus¹⁰ the particle behaviour of a system is constrained¹¹ in exactly the same way.

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