Using a mechanical or electronic stopwatch included with every mobile phone is the easiest way to count the seconds between “before”, “now” and “after” time points. But in the strange quantum world that obeys the principles of uncertainty, there may be no “after” point, just blurred in the “fog of possibilities”. And, of course, no stopwatch can measure such an indefinite amount of time.

But a suitable solution was found by scientists from Uppsala University, Sweden. They used the wave structure of the Rydberg atom as a measure of time intervals, which did not require an exact setting of the initial reference point.

Rydberg atoms are atoms of conventional chemical elements inflated to huge sizes. The electrons of these atoms are excited by laser light at the maximum possible energy state and move into orbit at the maximum diameter. The process of obtaining the Rydberg state is very delicate and not every laser is suitable.

The energy of the laser light beam must increase gradually to allow the electrons to transition to the next energy level. If there is not enough light energy, the electron will not move to the next level, if it is too much, the electron will be ejected from the atom and become a free electron and the atom will turn into an ion. .

However, atoms placed in the Rydberg state show a number of unique properties that developers of quantum systems and devices operating on exotic bases use for their purposes. The mathematical rules governing the behavior of Rydberg atoms have a general name – the Rydberg wavepack.

Like ordinary waves in the classical physics world, Rydberg wave packets are oscillations that create unique interference patterns. And if you send several Rydberg wave packets into a “quantum reservoir”, patterns of their oscillations will form and the picture created can be used to measure ultra-short time intervals.

In this case, the scientists used helium atoms converted into Rydberg atoms, and the interference pattern was recorded with a special spectrograph, and the points where time was measured between events were recorded.

“When using a normal timer, we have to start it at the beginning of the countdown and stop it at the end” – the scientists write, – “In our case, it’s enough to just look at the interference structure and say – well, 4 nanoseconds passed between these two events.”

Using such an unusual method, Swedish scientists were able to measure time intervals between events, lasting 1.7 trillionths of a second. And in the future, scientists plan to replace helium atoms with atoms of other elements, use laser pulses of different energies to increase the resolution of time measurement, and adapt this technology to work in a wider range of environmental conditions. Source