When entangled atoms are separated, quantum measurements become sharper, enabling unprecedented precision in spatial field measurements.
Using up to three entangled atomic clouds, researchers have overcome quantum noise in spatial field measurements, marking a significant advancement in precision.
Measuring the world with precision is challenging due to the inherent noise at very small scales and the rules of quantum physics, which introduce uncertainty even in the best instruments. This limits the accuracy of measurements in various fields, including electromagnetic fields, gravity, and time.
A groundbreaking study has revealed that quantum entanglement can revolutionize these limitations. By linking atoms in different locations, the researchers have achieved a breakthrough in measuring how physical quantities change across space with remarkable precision.
This innovative approach transforms a theoretical concept into a practical method, promising to enhance some of the most precise measuring tools ever developed.
"No one has previously performed such quantum measurements with spatially separated entangled atomic clouds, and the theoretical framework for these measurements was also unclear," Yifan Li, a postdoc researcher at the University of Basel, explained. "We have now extended this concept by distributing the atoms into up to three spatially separated clouds, allowing the effects of entanglement to act at a distance, similar to the EPR paradox."
The experiment began with atoms cooled to extremely low temperatures, where quantum effects dominate. Each atom behaves like a tiny spinning magnet, responding to electromagnetic fields and acting as a sensitive probe of its surroundings.
In typical scenarios, random quantum fluctuations in multiple atoms measured independently limit accuracy. To overcome this, physicists employ entanglement, a quantum phenomenon that correlates particles' behavior even when they are far apart.
Previous experiments had utilized entanglement to enhance measurements but only when all atoms were in the same place. This limitation meant scientists could measure a single location accurately but not how a field changes from one position to another.
The researchers addressed this challenge by altering the sequence of operations. They started with a single cloud of ultracold atoms, entangled their spins while the atoms were still together, and then divided the cloud into smaller parts, placing them in different locations.
Surprisingly, the entanglement survived the separation, enabling the distant atomic clouds to continue behaving as part of a single quantum system, mirroring the long-distance correlations in the Einstein–Podolsky–Rosen (EPR) paradox.
Each separated cloud sensed a distinct portion of an electromagnetic field. By combining information from all locations, the researchers could determine how the field varied in space. The entanglement reduced the usual quantum uncertainty, and disturbances affecting all atoms equally canceled out.
The team also developed the theoretical framework needed to describe such measurements, demonstrating how uncertainty can be minimized when multiple parameters are estimated simultaneously using spatially distributed entanglement.
The practical applications of this work include a new type of quantum sensor, which can be applied to optical lattice clocks and atom-based gravimeters. By reducing errors caused by atom position variations, these clocks and gravimeters can achieve even higher accuracy.
However, the proposed approach is technically demanding, requiring extreme stability and precision to maintain entanglement while splitting and controlling multiple atomic clouds. Extending the method to larger distances or more measurement points will be challenging.
The researchers plan to refine their protocols and test them in real-world precision instruments. The study, published in the journal Science, has been a significant step forward in quantum measurement technology.
