Researchers have developed a quantum watch: a quantum system that has a unique way to measure time. It doesn’t need a reference time or a repeating pattern to provide a measurement of the elapsed time – and they weren’t even looking to demonstrate such a timepiece.
The easiest analogy to understand how it works would be to consider it similar to a ruler or a tape measure. In a regular watch, the time markers are down to a beat, whether mechanical or electronic, which corresponds to the smallest unit of time that the device can measure. The accumulation of its repetition gives you timing. On a ruler, every distance is written out. Your ruler is not counting how many millimeters have ever been between this point and that point. You don’t have to go and look where it started.
The quantum watch is like that. The time of an event doesn’t depend on a specific beat but on the evolution of a quantum system made of Rydberg atoms. This is measured by laser pulses. These atoms are a special type of excited state where electrons occupy orbitals that are much further away from the nucleus than usual. They can be used to create molecular bonds that are longer than some bacteria, and they have numerous technical applications.
The quantum watch works because it can tell how long this Rydberg state in helium atoms has lived. The state is brief for human timings – but compared to the very short intervals of time in which quantum mechanical processes happen, it would be like comparing one second to tens of millions of years.
“This is just a new way of observing time. It’s not going to beat optical atomic clocks, it is just a new way of detecting time,” co-author Johan Söderström, from Uppsala University, told IFLScience.
Lead author Marta Berholts, from Tartu University, conducted a lot of the data collection during the pandemic lockdowns. Having just moved to Uppsala University, and not knowing people in the country, she had lots of time to work on the experiment. The experiment itself was not about finding a quantum watch, and the team has more results to publish about the work.
“We didn’t think of the possibility that we would use it as a watch,” Söderström told IFLScience. “That is something that came out after we looked at the data with some fairly simple theoretical modeling. [The quantum watch] turned out to be surprisingly exact.”
The team has not considered if there are realistic applications for the quantum watch. Rydberg states are useful in quantum computers so there might be intriguing applications there for somebody to find.
The work is published in Physical Review Research.