The world of quantum physics, although fascinating, is often difficult to understand. Among the discoveries that have advanced our understanding of the atom, the observation of Lamb shift in 1947 by physicists Willis Lamb and Robert Retherford remains a fundamental step. This phenomenon, a small energy difference between two energy levels of a hydrogen atom, has led to a revision of our theories about the structure of matter. However, more than 70 years after this discovery, scientists continue to refine theoretical calculations to better understand this phenomenon and its implications. Recently, a team of German researchers took a new step by improving the accuracy of Lamb shift calculation, paving the way for new discoveries in fundamental physics.
What is Lamb shift?
In 1947, Willis Lamb and Robert Retherford observed a small difference between two energy levels in a hydrogen atom, the 2S 1/2 level and the 2P 1/2 level. According to the principles of classical physics, these two levels should be identical. However, their measurement reveals a tiny shift, with an amplitude of a few kilohertz.
This deviation, although tiny, overturns classical theories of the atom and opens the way to new perspectives. THE Lamb shiftas it is now called, is not simply an anomaly; it is proof that another dimension, which classical physics cannot explain, influences particles at the atomic scale.
The Lamb shift thus illustrates how, on a microscopic scale, the laws of quantum mechanics govern matter in a way that is radically different from what we perceive in our daily lives. This phenomenon has become a crucial tool for understanding the foundations of modern physics. Beyond simple observation, it allows scientists to rewrite part of our understanding of the universe and refine the precision of theories about elementary particles.
QED and the interaction with the quantum vacuum
This phenomenon leads to the birth of quantum electrodynamics (QED), a theory that describes the interactions between electrons and photons.
In detail, it is based on the idea that the electron does not evolve in an empty vacuum, but constantly interacts with a fluctuating energy field, called a “quantum vacuum”. These quantum fluctuations can produce virtual particles, particles that appear and disappear on an extremely short time scale. The Lamb shift is actually a consequence of these vacuum fluctuations, which change the energy levels of the atom. Understanding precisely how these effects influence the energy of the electron is crucial for the accuracy of calculations in atomic physics.
Theoretical challenges in Lamb shift calculations
Calculating this small difference in energy was not an easy task. QED is an extremely complex theory, and the calculations required to accurately predict the Lamb shift are riddled with mathematical challenges. One of the biggest obstacles was related to divergences which appear in certain mathematical terms used to describe interactions between particles. These discrepancies make the calculation results infinitely large at certain energy levels, making theoretical predictions difficult and uncertain. Scientists had to use sophisticated techniques, such as Feynman diagrams, to “cancel out” these discrepancies and obtain more accurate results.
Feynman diagrams are a kind of visual language that allows interactions between particles to be represented as lines and symbols. These diagrams make QED calculations more manageable, but they are not without challenges. For example, the two-loop correction refers to a special type of diagram that describes how two virtual photons interact with an electron, and which has significant effects on the calculation of the Lamb shift.
Recent advances in the calculation of the Lamb shift
That being said, a team of researchers from the Max Planck Institute for Nuclear Physics in Germany recently took a leap forward in calculating the Lamb shift. Led by Vladimir Yerokhin, this team was able to calculate with greater precision the effect of two-loop correction on the Lamb shift. Using state-of-the-art numerical methods, they improved theoretical shift predictions by reducing uncertainty in the calculations. In doing so, they were able to reduce the frequency difference of the Lamb shift by 2.5 kHza significant improvement for such a precise phenomenon.
But that's not all. The team also developed methods to calculate the Rydberg constant with greater precision. The Rydberg constant is one of the fundamental constants of physics, which determines the wavelengths of the spectral lines of hydrogen. By refining the precision of Lamb shift calculations, researchers have also refined this constant, which is essential for improving our measurements of atomic properties.
Why are these improvements important?
These recent improvements in Lamb shift calculations not only have implications for the accuracy of atomic measurements; they also have implications for other areas of fundamental physics. For example, they could influence calculations of the effects of magnetic moment abnormal of the electron and muona subatomic particle similar to the electron. These calculations are essential for testing the limits of the Standard Model of particle physics, and experiments like the Muon g-2 experiment at Fermilab seek to verify these predictions with pinpoint precision. If deviations are observed, this could indicate the existence of new particles or interactions, beyond the standard model.
Furthermore, this new approach could also have practical applications in cutting-edge technologies such as quantum computers, where a precise understanding of the quantum properties of particles is essential for the development of new types of calculations and communication.
