An international team of researchers has made significant strides in controlling hybrid electron-photon quantum states within helium atoms. This advancement was made possible by generating intense pulses of extreme ultraviolet radiation. This approach not only allows for the exploration of quantum mechanical phenomena in various atoms and molecules but also provides a means to manage chemical reactions.
Led by Dr. Lukas Bruder, a junior research group leader at the Institute of Physics, University of Freiburg, an international group of scientists successfully created and gained direct control over hybrid electron-photon quantum states in helium atoms. They achieved this by generating specially crafted, high-intensity extreme ultraviolet light pulses through the FERMI free electron laser located in Trieste, Italy. The researchers utilized an innovative laser pulse-shaping technique to manipulate these hybrid quantum states. Their findings have been published in the journal Nature.
Intense light fields can produce new quantum states
Electrons tied to an atom can only possess specific energy levels, primarily determined by the atom itself. However, when an atom is exposed to a powerful laser, these energy levels can shift, leading to the formation of hybrid electron-photon states, also referred to as ‘dressed states’. These states emerge at laser intensities ranging from ten to one hundred trillion watts per square centimeter. To create and control these unique quantum states, laser pulses that achieve these high intensities within a brief time span of just a few trillionths of a second are essential.
Utilizing free electron lasers for extreme ultraviolet radiation
In their study, the scientists employed the FERMI free electron laser, which produces laser light in the extreme ultraviolet spectrum at extremely high intensities. The radiation generated in this region has a wavelength shorter than 100 nanometers, a crucial factor for affecting the electron states within helium atoms.
To effectively manage the electron-photon states, the team utilized laser pulses that either expanded or contracted based on the situation. They accomplished this by adjusting the timing of the various color components of the laser light. The attributes of these laser pulses were fine-tuned through a ‘seed laser pulse,’ which prepared the emissions from the free electron laser.
“This research has allowed us to control these fleeting quantum states in a helium atom for the first time,” states Bruder. “The technique we’ve developed paves the way for a new area of study: it offers enhanced efficiency and selectivity for experiments utilizing free electron lasers and provides fresh insights into fundamental quantum systems that are inaccessible with visible light. This may even lead to methods for studying or precisely controlling chemical reactions at the atomic level.”
