Determining the passage of time in our world of ticking clocks and oscillating pendulums is a simple matter of counting the seconds between ‘then’ and ‘now’.
Down at the quantum scale of buzzing electrons, however, ‘then’ cannot always be predicted. Worse, the ‘now’ often recedes into a haze of obscurity. A stopwatch just isn’t going to work for some scenarios.
According to a 2022 study by researchers at Uppsala University in Sweden, a possible solution may be found in the shape of quantum fog itself.
His experiments on the wave-like nature of something called the Rydberg state revealed a new way of measuring time that does not require a precise starting point.
The Rydbergs are the over-inflated balloons of the nuclear particle kingdom. Instead of air blown by lasers, these atoms contain electrons in extremely high-energy states, orbiting away from the nucleus.
Of course, each pump of the laser isn’t required to puff the atom up to cartoonish proportions. In fact, lasers are routinely used to tickle electrons into high energy states for a variety of uses.
In some applications, a second laser may be used to monitor the change in the state of the electron with the passage of time. For example, these ‘pump-probe’ techniques can be used to measure the speed of some ultrafast electronics.
Inducing atoms into Rydberg states is a handy trick for engineers, at least when it comes to designing novel components for quantum computers. Needless to say, physicists have gathered a significant amount of information on the way electrons are pushed into the Rydberg state.
However, being quantum beasts, their moves are less like sliding beads on a tiny abacus, and more like an evening at the roulette table, where every roll and jump of the ball is squeezed into a game of chance. .
The mathematical rulebook behind this wild game of Rydberg electron roulette is known as the Rydberg wave packet.
As with real waves, interference occurs when more than one Rydberg wave packet ripples in a space, resulting in a unique pattern of waves. Throw enough Rydberg wave packets at the same atomic pond, and those unique patterns will represent the different times it takes each wave packet to evolve from each other.
It was these ‘fingerprints’ of time that the physicists behind this set of experiments set out to test, showing that they were consistent and reliable enough to serve as quantum timestamping.
Their research involved measuring the results of laser-excited helium atoms and matching their findings with theoretical predictions to show how their signature results could stand up to periods of time.
“If you’re using a counter, you have to define zero. You start counting at some point,” explained physicist Marta Berholts of Uppsala University in Sweden, who led the team. new scientist In 2022.
“It has the advantage that you don’t have to start the clock—you just look at the interrupt structure and say ‘Okay, it’s been 4 nanoseconds.'”
A guidebook to developing Rydberg wave packets that can be used in conjunction with other forms of pump-probe spectroscopy to measure phenomena on a smaller scale, when sometimes less obvious, or too inconvenient to measure .
Importantly, no fingerprint is needed then and now to serve as a start and end point for time. It would be like measuring the running of an unknown runner against several competitors running at a set pace.
By looking for signatures of interfering Rydberg states among a sample of pump-probe atoms, technicians can clock a timestamp for events as fleeting as just 1.7 trillion.
Future quantum clock experiments may replace helium with other atoms, or even use laser pulses of different energies, to broaden the guidebook of timestamps to suit a wider range of circumstances. .
Source: www.sciencealert.com
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