China claims more precise estimation of quantum quantities — ScienceAlert
Researchers at Shanxi University in China said they were able to simultaneously estimate two incompatible quantum quantities with precision approximately 20% beyond the Heisenberg uncertainty limit. The experimental results were published as a preprint that has not yet undergone peer review, ScienceAlert reports.
Data before and after measurement
The uncertainty principle, formulated by German physicist Werner Heisenberg in 1927, describes limits on precision for pairs of incompatible quantities. The best-known example is a particle’s position and momentum: the more precisely one of these quantities can be determined, the less certain the other becomes.
The authors used an approach in which data obtained both before and after a given moment were used to estimate the state of the system at that moment. The scientists suggested that this two-sided perspective could reduce uncertainty when reconstructing the state of a quantum system.
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Experiment with rubidium atoms
To test the method, the team used 52 billion rubidium atoms in a small glass chamber. One laser aligned the atoms’ spins—their magnetic properties. The atoms then behaved as a single quantum system, whose position and momentum the researchers measured with a second laser.
The measurements continued uninterrupted for 84 minutes. According to the authors, combining information from the past and future relative to a selected moment weakened the usual trade-off between the precision of estimating two incompatible quantities.
The researchers emphasize that the Heisenberg uncertainty principle has not been abolished. The proposed approach concerns refining the probable state of a system after additional data have been obtained, so it is not suitable for real-time monitoring. The method could potentially be useful for quantum sensors and systems where retrospective analysis is already used, including atomic clocks.
