Quantum jumps. Instantaneous or not?

Einstein and Schrödinger were both pioneers of quantum mechanics and both agreed on one thing. Quantum jumps, where a particle, energy or information instantaneously changes, were just too weird to deal with.

But nearly a century later, would you really still challenge the fact that this is an accepted part of how we understanding Physics?


Most of us wouldn’t, but scientists are bit of an unusual bunch to start with. Challenging founding principles is the foundation of science. Two weeks ago, a team at Yale published their results, not only showing that quantum jumps take time, but that they can also be partially predicted and even reversed during this travel time before they reach their destination state.

This group of researchers built an artificial atom that would perform jumps between an excited, higher-energy state and a lower energy state. In switching between the higher energy state down to the lower energy state, the atom would emit a photon (effectively a pure energy particle) which caused a clicking sound in their measuring equipment.

The tricky part of the setup is that it is impossible for us to directly observe an atom transitioning between states, due to some interesting laws of quantum mechanics. So they chose to measure a second high energy state that would tell them whether the atom was high energy or low energy at a certain time by the photon energy (light) would scatter in the measuring chamber.

A pattern was quickly observed. The clicks that were given off by photon emission would suddenly decrease in frequency just before the atom would jump to the low-energy state.

“As soon as the length of a no-click period significantly exceeds the typical time between two clicks, you have a pretty good warning that the jump is about to occur,” said Devoret, one of the researchers.

From here, it was a easier to observe the jump, simply by the cutting off the photons that they were allowing into the atom chamber and then studying the jump process in high detail. And guess what? The jump took time, and it could even be reversed.

It makes a lot of sense that these jumps have been originally thought to be instantaneous. Back in the time of Bohr, and the development of quantum mechanics, and even through the rest of the 20th century, measuring devices were not accurate enough to measure any time taken for such a quantum jump. And even if they were good enough to measure, it actually took this research group the need to find a pattern so they could “zoom in” on the exact moment the jump occurred to investigate exactly what was going on.

Talk about exciting new physics, and a revolutionary way of understanding quantum mechanics!



If you’re interested in reading more, you can read the full-text paper here!

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