What is it about?
Quantum electrodynamics is a quantum field theory which has been extremely successful at modeling simple atomic systems. So far, theorists have successfully calculated various atomic properties for the 5 lightest elements: hydrogen, helium, lithium, beryllium, and boron. These calculations are extremely difficult and require experimental confirmation. This experimental paper presents results for high precision spectroscopy on a transition in neutral beryllium and compares it to the theoretical prediction. Our result, combined with the theoretical prediction, confirms that quantum electrodynamics does accurately model the beryllium atom, to within the precision of the theoretical results.
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Why is it important?
While quantum electrodynamics has been extremely successful, we know that quantum field theory is not a complete model. For example, quantum field theory does not include gravity, describe dark matter or dark energy, explain baryon asymmetry (why is there more matter than anti-matter?), etc. Many groups, including our group here at Smith College, test the theory to see if it works for a given system. This paper not only tests the theoretical prediction, but also gives theorists a more precise answer to compare future, more accurate calculations.
Perspectives
It is an interesting question to ponder what system will eventually show cracks in quantum electrodynamics (QED). No one expected our result to disagree with the predictions from quantum electrodynamics, so why did we put in all this effort? In a sense, this paper contributes to the effort to test QED in ever more complex systems. Beryllium is a four electron system; each electron interacts with every other electron as well as the nucleus. Other experiments in atomic physics test quantum field theory in different ways. Probably the most well known, and in my opinion the most likely to find cracks, is measuring the electric dipole moment (EDM). Even though EDM measurements are extremely important and most likely to (eventually) measure a disagreement with our best models, it is still important to test quantum field theory in all possible ways, including increasing the complexity of the system.
Will Williams
Smith College
Read the Original
This page is a summary of: Testing Quantum Electrodynamics in the Lowest Singlet State of Neutral Beryllium-9, Physical Review Letters, August 2018, American Physical Society (APS),
DOI: 10.1103/physrevlett.121.053001.
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