Australian and British physicists are transforming how scientists approach quantum measurements by overcoming one of its biggest challenges, Heisenberg’s uncertainty principle.
The new research has demonstrated how scientists can precisely measure position and momentum of a particle at the same time. The researchers hope this new method could help develop ultra-precise sensor technology which may be used to improve navigation, medicine and astronomy.
“Just as atomic clocks transformed navigation and telecommunications, quantum-enhanced sensors with extreme sensitivity could enable whole new industries,” says Dr Christopher Valahu from the Quantum Control Laboratory team at the University of Sydney, Australia.
Heisenberg’s uncertainty principle says that you cannot know both a particle’s position and momentum with absolute precision at the same time. The more precisely you measure one of the particle’s properties, the less you know about the other.
When the principle was first discovered by Werner Heisenberg, it changed how scientists approached quantum physics as it means being able to precisely measure both the position and momentum of a particle is impossible.
The researchers may have found a way to bypass the uncertainty.
“Think of uncertainty like air in a balloon,” says Dr Tingrei Tan, who led the study from the University of Sydney’s Nano Institute.
“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.”
The approach was first outlined theoretically in 2017, with Tan’s team now performing the first experimental demonstration. The team were able to conduct the experiment using a technological approach they had engineered in a previous study for error-corrected quantum computers.
“Ideas first designed for robust quantum computers can be repurposed so that sensors pick up weaker signals without being drowned out by quantum noise,” says Professor Nicolas Menicucci, a co-author of the study from RMIT University.
“It’s a neat crossover from quantum computing to sensing.”
The team used the microscopic vibrational motion of a trapped ion to implement the sensing protocol. These ions were prepared in ‘grid states’, the type of states used in error-corrected quantum computing.
These grid states are then able to measure tiny signals that indicate position and momentum. The measurements were collected with a precision better than the best achieved using only classical sensors.
“By applying this strategy in quantum systems, we can measure the changes in both position and momentum of a particle far more precisely,” says Valahu.
“We give up global information but gain the ability to detect tiny changes with unprecedented sensitivity.”
It’s this ability to detect miniscule changes that the team suggest could influence the future of technology. They suggest precise quantum sensors could help improve navigation systems deep underground, in submarines or even in space where typical GPS isn’t as effective. It may also help enhance medical and biological imaging.
“We haven’t broken Heisenberg’s principle. Our protocol works entirely within quantum mechanics,” said Dr Ben Baragiola, co-author from RMIT.
“The scheme is optimised for small signals, where fine details matter more than coarse ones.”
The researchers are hopeful that this breakthrough will open the door to developing a more effective quantum sensing toolbox.
“This work highlights the power of collaboration and the international connections that drive discovery,” says Tan.
The results from this study have been published in Science Advances.