Mexican physicist verifies quantum theory on the uncertainty principle

The Mexican physicist Manuel Fernández Guasti managed to experimentally verify, for the first time, the Heisenberg uncertainty principle, a fundamental idea of ​​quantum mechanics proposed by Werner Heisenberg in 1927.

This theoretical principle says that position and momentum cannot be measured simultaneously and with absolute precision (momentum) of a particle, a limitation that does not depend on the quality of the instruments, but on the nature of matter and energy itself.

“Designing a system that could measure position and momentum at the same time was a challenge that took us seven years of constant work,” explained Fernández Guasti in an interview with The Day, in the context of the International Year of Quantum Science and Technology, which will be celebrated in 2025.

To achieve this, the researcher used two highly precisely stabilized lasers and a special camera capable of recording the arrival of each photon in tiny fractions of a second. This made it possible to see interference patterns formed by white dots, each corresponding to a photon.

Then, by changing the size of the aperture through which the light passed – between 0.36 and 10 millimeters – the scientists verified that, when the position is measured with greater precision, the uncertainty in the impulse increases, and vice versa, as established by theory.

“These results not only directly confirm a fundamental principle of quantum mechanics, but also open new routes to explore the border between classical and quantum,” says the article published in Physics Letters Aa magazine specialized in theoretical and experimental research in frontier physics.

Until now, the usual way to try to demonstrate the uncertainty principle has been through light diffraction experiments. In them, position is measured at one point and momentum at another; Furthermore, at a different time.

Fernández Guasti stressed that what distinguishes his experiment from the previous ones is that in it “position and momentum are measured in the same region of space and time. The light that reaches the detector does so in an area of ​​about 8 millimeters, and it is there, in that same place and at the same time, where we are measuring the two variables.”

The biggest challenge, he added, was “to design an extremely stable optical arrangement and make the interference of the two lasers perfect. Any vibration, any deviation, ruined the simultaneity.”

At this point, the work of Carlos Mario García Guerrero, technician at the Quantum Optics Laboratory at the UAM-Iztapalapa, and Ruth Diamant Adler, doctor in physics, in experimental development stood out.

Fernández Guasti considers that the result of this research will influence future investigations of quantum optics and the study of the limits of quantum measurement.