Determining the passage of time in our world of ticking clocks and swinging pendulums is a simple case of counting the seconds between “then” and “now”.
At the quantum scale of buzzing electrons, however, “then” cannot always be anticipated. Worse still, “now” often becomes a blur. A stopwatch just won’t work in some scenarios.
A potential solution could be found in the very form of quantum fog itself, according to a 2022 study by researchers at Uppsala University in Sweden.
Their experiments on the wave nature of what is called a Rydberg state revealed a new way of measuring time that does not require a precise starting point.
Rydberg atoms are the overinflated balloons of the kingdom of particles. Blown up with lasers instead of air, these atoms contain electrons in extremely high energy states, orbiting away from the nucleus.
Of course, not all the pumps of a laser need to pump up an atom to cartoonish proportions. In fact, lasers are commonly used to tickle electrons into higher energy states for a variety of uses.
In some applications, a second laser can be used to monitor changes in electron position, including the passage of time. These ‘pump-probe‘ can be used to measure the speed of certain high-speed electronic devices, for example.
Inducing atoms into Rydberg states is a handy tip for engineersespecially when it comes to designing new components For quantum computers. Needless to say, physicists have amassed a significant amount of information about how electrons move when pushed into a Rydberg state.
Being quantum animals, however, their movements feel less like pearls sliding on a small abacus, and more like an evening at the roulette table, where every roll and jump of the ball is compressed into a single game of chance.
The mathematical rulebook behind this wild game of Rydberg electronic roulette is called a Rydberg wave packet.
Just like real waves, having more than one Rydberg wave packet rippling through a space creates interference, resulting in unique patterns of ripples. Launch enough Rydberg wavepackets into the same atomic basin, and these unique patterns will each represent the distinct time required for the wavepackets to evolve relative to each other.
It is these same “fingerprints” of time that the physicists behind this set of experiments set out to test, showing them to be consistent and reliable enough to serve as a form of quantum timestamp.
Their research involved measuring the results of laser-excited helium atoms and matching their findings with theoretical predictions to show how their signature results might last for a while.
“If you’re using a counter, you have to set zero. You start counting at some point,” explained physicist Marta Berholts from Uppsala University in Sweden, who led the team. new scientist in 2022.
“The advantage of this is that you don’t have to start the clock – you just look at the interference structure and say ‘okay, that’s 4 nanoseconds. “”
An evolving Rydberg wavepacket guide could be used in combination with other forms of pump-probe spectroscopy that measure minute-scale events, when occasionally less clear, or just too impractical to measure.
Importantly, none of the fingerprints require a past and a now to serve as a start and end point for time. It would be like measuring the race of an unknown sprinter against a number of competitors running at set speeds.
By looking for the signature of interfering Rydberg states in the middle of a sample of pump-probe atoms, technicians were able to observe a timestamp for events as fleeting as 1.7 trillion seconds.
Future quantum watch experiments could replace helium with other atoms, or even use laser pulses of different energies, to broaden the guide of timestamps to accommodate a wider range of conditions.
This research was published in Physical examination research.
An earlier version of this article was first published in October 2022.