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In a world of ticking clocks and swaying pendulums, marking the passage of time is as easy as keeping track of the seconds between “then” and “now.” But ‘then’ can’t always be predicted down at the quantum size of buzzing electrons. Even worse, “now” frequently dissolves into a cloud of doubt. In some situations, a stopwatch will not enough. Researchers from Uppsala University in Sweden believe that the structure of the quantum fog itself may hold the key to finding a solution.
They have discovered a fresh approach to measure time that doesn’t require a specific starting point through their research on the wave-like properties of something known as a Rydberg state. The overinflated balloons of the particle kingdom are rydberg atoms. These atoms are inflated with lasers rather than air and have electrons orbiting far from the nucleus in extremely high energy states. Of course, not every laser pulse has to inflate an atom to comical heights. In reality, a range of applications frequently include the employment of lasers to nudge electrons into higher energy states.
In rare circumstances, a second laser can be employed to keep track of time-related changes in the electron’s position. These “pump-probe” methods can be used, for example, to gauge the speed of some ultrafast devices. Engineers can use the ability to induce Rydberg states in atoms to their advantage, not least when creating unique parts for quantum computers. It goes without saying that physicists have learned a lot about how electrons behave when pushed into a Rydberg state. However, because they are quantum animals, their actions resemble an evening spent playing roulette rather than beads sliding around on a tiny abacus. Every ball roll and hop 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 in a pond, interference caused by multiple Rydberg wave packets in an area leads to different patterns of ripples. If you combine enough Rydberg wave packets, the resulting individual patterns will each indicate the unique amount of time it takes for the wave packets to evolve in unison. The physicists behind this most recent series of experiments set out to verify these particular “fingerprints” of time, demonstrating that they were dependable and consistent enough to be used as a type of quantum timestamping.
To demonstrate how their distinctive results could hold up over time, their research involves measuring the outcomes of laser-excited helium atoms and comparing their results with theoretical expectations. “Zero must be defined if a counter is being used. At some point, you begin counting, “The team’s leader, Swedish physicist Marta Berholts from the University of Uppsala, stated to New Scientist. The advantage of this is that you don’t need to start the clock; instead, you can simply glance at the interference structure and note that 4 nanoseconds have passed.
With other types of pump-probe spectroscopy that measure events on a minute scale when now and then are less clear or are just too inconvenient to measure, a guide book of changing Rydberg wave packets could be utilized. It’s important to note that none of the fingerprints require 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 running 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 signature of interfering Rydberg states among a sample of pump-probe atoms. Future quantum watch experiments could use laser pulses of various intensities or possibly other atoms in place of the helium to expand the timestamp rule book to accommodate a wider range of circumstances.