A recent study led by researchers at the University of Sydney has introduced a novel approach to the long-standing Heisenberg’s uncertainty principle, significantly enhancing the capabilities of quantum sensors. Published in Science Advances, the research outlines how scientists can navigate the inherent limitations of quantum measurements by redistributing uncertainty rather than eliminating it. This breakthrough could pave the way for a new generation of ultra-precise sensors that operate at atomic scales.
For nearly a century, Heisenberg’s principle has dictated that one cannot simultaneously know a particle’s position and momentum with absolute precision. The more accurately one is measured, the less certain the other becomes. This principle has often been viewed as a limitation, but the research team, which includes Sydney Horizon Fellow and ARC Future Fellow from the Quantum Control Laboratory, proposes a different perspective.
Reconceptualizing Uncertainty in Measurements
The researchers liken the uncertainty in quantum measurements to air in a balloon: while the total amount of air (or uncertainty) remains constant, it can be shifted around. This reshaping allows for a more flexible approach to measurement. Traditionally, scientists faced a trade-off; if they focused on precisely measuring position, they lost information on momentum, and vice versa. The new method enables simultaneous tracking of both parameters by cleverly manipulating the uncertainty.
To illustrate this concept, the researchers use the analogy of a clock with a single hand. If the hand indicates the hour, the hour is known precisely, but the minutes remain vague. Conversely, if it indicates minutes, the hour becomes uncertain. By applying this principle to quantum measurements, the team can effectively monitor small changes in both position and momentum—even if the absolute position remains unknown.
Breakthrough Experiment with Trapped Ions
The research utilized a trapped ion, a single electronically charged atom controlled through electric and magnetic fields. By preparing the ion in what they call “grid states,” a quantum state initially developed for error-corrected quantum computing, the team transformed these states into a sensor capable of measuring tiny signals.
The experiment demonstrated an impressive capability to measure an uncertainty in a signal corresponding to half a nanometre—approximately the size of an atom. Additionally, the researchers achieved measurements of forces at the scale of yoctonewtons, which equates to a trillionth of a trillionth of a newton. To put this into perspective, this level of sensitivity is akin to measuring the weight of about 30 oxygen molecules.
The implications of such precision are profound. By enabling the measurement of minuscule signals, this research not only enhances the field of quantum sensing but also promises to deepen our understanding of cosmic phenomena. Quantum sensors are already instrumental in gravitational-wave observatories that detect events like colliding black holes, and this new method could significantly expand their capabilities.
While the current findings remain confined to a laboratory setting and are not ready for commercial application, the researchers are optimistic. This innovative approach to measurement could lead to a new generation of ultra-sensitive quantum sensors, transforming various scientific fields and enhancing our grasp of the universe.
