An international team of physicists has found a way to “sidestep” the Heisenberg Uncertainty Principle, which posits that it is impossible to measure a particle’s location and momentum simultaneously.
The team’s work has revealed a method to redistribute quantum uncertainty so that tiny changes in a particle’s position and momentum can be measured simultaneously with precision beyond the standard quantum limit—all without violating Heisenberg’s famous uncertainty principle.
The research team behind the landmark achievement suggests their findings could offer new avenues of research in ultra-precise sensing at previously unattainable levels, which could enable deep space navigation, medical imaging, and potential military applications like submarine navigation.
When German physicist Werner Heisenberg first postulated the uncertainty principle in 1927, the technology to test its validity was in the early stages. Since then, several experiments have confirmed the seeming impossibility of simultaneously sensing certain particle property pairs, such as momentum and location. The more closely one property is measured, the less certainty there is about the paired property.
Curious if they could find a way to sidestep Heisenberg to precisely measure a particle’s momentum and location, a team led by Dr. Tingrei Tan from the University of Sydney Nano Institute and School of Physics developed a dedicated experiment. According to a statement detailing the team’s work, the group built a system designed to monitor the tiny vibrational state of a trapped ion, a setup the researchers described as “the quantum equivalent of a pendulum.”
Next, the team tapped into Dr. Tan’s previous work on error-corrected quantum computing to prepare the ion in “grid states.” By fine-tuning the setup, the team successfully showed that the momentum and position of the ion could be measured with a level of precision they described as beyond the “standard quantum limit.” This limit is considered the best achievable precision using only classical (non-quantum) sensors.
“It’s a neat crossover from quantum computing to sensing,” said co-author Professor Nicolas Menicucci, a theorist from RMIT University. “Ideas first designed for robust quantum computers can be repurposed so that sensors pick up weaker signals without being drowned out by quantum noise.
Although exceeding the standard quantum limit may appear to directly violate Heisenberg’s uncertainty principle, Dr. Ben Baragiola, a study co-author from RMIT, said they haven’t actually broken any laws of physics; they have simply found a way around them.
“We haven’t broken Heisenberg’s principle,” he explained. “Our protocol works entirely within quantum mechanics.”
To explain the team’s sidestepping of Heisenberg, Dr. Tan said to think of uncertainty like the air inside a balloon.
“You can’t remove it without popping the balloon, but you can squeeze it around to shift it. That’s effectively what we’ve done. We push the unavoidable quantum uncertainty to places we don’t care about (big, coarse jumps in position and momentum) so the fine details we do care about can be measured more precisely.”
Another analogy offered by the research team involves a pair of clocks. Unlike a typical clock with two hands, one of the clocks has only a minute hand, and the other has only an hour hand. The hour hand clock provides a general indication of the hour, but the minute measurement is less precise. Conversely, the clock with only a minute hand gives a more precise yet less specific measurement, but the “larger context” of the lost. The team notes that this modular measurement ability “sacrifices some global information in exchange for much finer detail.”
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