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In our world of moving timepieces and swinging pendulums, telling the
difference between "then" and "now" is as easy as counting the
seconds.
But 'then' can't always be predicted down at the subatomic size of buzzing
electrons. Even worse, "now" frequently turns into an ambiguous cloud. In
some situations, a timer will not be effective.
The shape of the quantum fog itself may hold the key to an answer,
according to a 2022 investigation by scientists at Sweden's Uppsala
University.
They discovered a novel method to quantify time that doesn't require an
exact beginning point through experiments on the wave-like properties of
something called a Rydberg state.
The overinflated balloons of the subatomic world are
rydberg atoms. These atoms are inflated with lasers rather than air and have electrons
orbiting far from the center in exceptionally high energy states.
Of course, not every laser pulse has to inflate an atom to ludicrous
heights. In reality, a variety of applications frequently involve the use of
lasers to nudge electrons into higher energy levels.
In some circumstances, a second laser can be used to keep track of
time-related variations in the electron's location. These "pump-probe" methods can be used, for example, to gauge the speed of some rapid
devices.
Engineers can use the ability to induce Rydberg states in atoms to their
advantage, not least when creating innovative parts for quantum computers.
It goes without saying that scientists have learned a lot about how
electrons behave when pushed into a Rydberg state.
However, because they are quantum animals, their motions resemble an
evening spent playing roulette rather than beads sliding around on a small
abacus. Every ball roll and leap is combined into a single game of
chance.
Rydberg wave packets are the mathematical playbook for this crazy game of
Rydberg electron roulette.
Similar to real waves, interference occurs when multiple Rydberg wave
packets are present in an area, producing different patterns of
disturbances. If you combine enough Rydberg wave packets, the resulting
distinct patterns will each reflect the unique amount of time it takes for
the wave packets to develop in unison.
The purpose of this series of tests was to test these very "fingerprints"
of time and demonstrate that they were reliable and consistent enough to be
used as a type of quantum timestamping.
To demonstrate how their distinctive results could hold up over time, their
study involved measuring the outcomes of laser-excited helium atoms and
comparing their results with theory forecasts.
"Zero must be defined if a number is being used. At some point, you begin
tallying, "In 2022, the team's leader and scientist Marta Berholts from the
University of Uppsala in Sweden spoke with
New Scientist
about their findings.
The advantage of this is that you don't need to initiate the clock;
instead, you can simply glance at the interference structure and note that 4
nanoseconds have passed.
A guidebook of changing Rydberg wave packets could be used in conjunction
with other types of pump-probe spectroscopy that measure events on a small
scale, when now and then are less obvious, or simply too cumbersome to
measure.
It's important to note that none of the signatures necessitate a then and
now to act as a temporal beginning and end. It would be comparable to
evaluating a sprinter's performance against a group of opponents who were
all racing at the same pace.
Technicians were able to determine a timestamp for events that happened in
the course of just 1.7 trillionths of a second by searching for the hallmark
of interfering Rydberg states among a collection of pump-probe atoms.
Future quantum watch tests might use laser pulses of various energies
instead of helium or even other atoms to expand the timestamps' rulebook to
accommodate a wider variety of circumstances.
This research was published in
Physical Review Research.
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