An international team of physicists has pushed the boundaries on ultra-precise measurement by harnessing quantum light waves in a new way.
It is one thing to be able to measure spectacularly small distances using “squeezed” light, but it is now possible to do this even while the target is moving around.
Leader of the international theoretical team, Prof. Howard Wiseman from Griffith Univ.’s Centre for Quantum Dynamics, says this more precise technique for motion tracking will have many applications in a world that is constantly seeking smaller, better and faster technology.
“At the heart of all scientific endeavor is the necessity to be able to measure things precisely,” Wiseman says. “Because the phase of a light beam changes whenever it passes through or bounces off an object, being able to measure that change is a very powerful tool. By using squeezed light we have broken the standard limits for precision phase tracking, making a fundamental contribution to science. But we have also shown that too much squeezing can actually hurt.”
Dominic Berry from Macquarie Univ. has been collaborating with Wiseman on the theory of this problem for many years.
“The key to this experiment has been to combine “phase squeezing” of light waves with feedback control to track a moving phase better than previously possible,” Berry says.
“Ultra-precise quantum-enhanced measurement has been done before, but only with very small phase changes. Now we have shown we can track large phase changes as well,” he says.
Prof. Elanor Huntington from UNSW Canberra, who directed the Australian experimental contribution, is a colleague of Wiseman in the Centre for Quantum Computation and Communication Technology.
“By using quantum states of light we made a more precise measurement than is possible through the conventional techniques using laser beams of the same intensity,” Huntington says. “Curiously, we found that it is possible to have too much of a good thing. Squeezing beyond a certain point actually degrades the performance of the measurement, making it less precise than if we had used light with no squeezing.”