A new method enables simultaneous measurement of a particle’s position and momentum with greater precision than the standard quantum limit. This approach circumvents Heisenberg’s uncertainty principle and opens up possibilities for creating unique, highly accurate sensors.

The Uncertainty Principle and Its Limitations

At the heart of quantum mechanics lies the uncertainty principle, formulated by Werner Heisenberg in 1927. According to this principle, it is impossible to know certain pairs of a particle’s properties—such as its position and momentum—with absolute precision at the same time. The more precisely one property is determined, the less precisely the other can be known. This is not a flaw of measuring instruments, but a fundamental property of nature.

This limitation creates a natural barrier for the development of ultra-sensitive technologies: the accuracy of any measurement ultimately runs into the so-called “standard quantum limit”—the maximum result achievable by classical methods. To overcome this limit, new strategies are needed that “outsmart” nature without violating its laws.

A New Approach to Measurement

A team of physicists from Australia and the UK has proposed an innovative method, with results published in the journal Science Advances. The researchers did not violate Heisenberg’s principle, but found a way to bypass it by redistributing the unavoidable quantum uncertainty. They compared this process to air in a balloon: you can’t remove the air without popping the balloon, but you can squeeze and shift it to another part. The scientists “displaced” the uncertainty into measurement areas that were not important for their purposes, allowing them to record tiny changes of interest with high precision.

Experimental Implementation

In the experiment, the team used the oscillations of a single ytterbium ion, which acted as a quantum pendulum. Using lasers, the ion was prepared in a special “grid state” borrowed from quantum computing. Instead of directly measuring position and momentum, the researchers determined their “modular” analogues.

This can be likened to rolling up an infinite ruler into a ring: you lose information about which “turn” a point is on, but gain the ability to pinpoint its position within the ring with great accuracy. Similarly, the researchers gave up global information about the system to focus on measuring the smallest changes. The key trick is that these new modular variables, when properly configured, become compatible (commuting), so the usual uncertainty limitation does not apply, allowing them to be measured simultaneously.

Visualization and Results

The ytterbium ion was prepared in a non-classical “grid state,” which on a graph appears as a regular array of sharp peaks—each peak corresponding to specific modular values of position and momentum. The scientists subjected the ion to small displacements and measured changes in its state. When an external influence was applied, the entire grid shifted by a tiny amount, and by tracking this shift with laser manipulations, the physicists could determine changes in both position and momentum at the same time, with precision exceeding the standard quantum limit.

The method was also tested on another pair of incompatible quantities—particle number and phase. As a result, the measurement accuracy surpassed the standard quantum limit by 5.5 decibels for the “position–momentum” pair and by 3.2 decibels for the “number–phase” pair.

Prospects and Applications

Although this work is still at the laboratory stage, it demonstrates a new foundation for future sensor technologies. This approach does not replace existing methods, but expands the toolkit of quantum metrology.

Technologies based on this principle could lead to the creation of ultra-sensitive sensors for navigation in GPS-denied environments—such as on submarines or in space—as well as for medical imaging, studying gravitational waves, and searching for dark matter.