Reviewed by Lexie CornerDec 13 2024
An international group of researchers from the University of Freiburg's Institute of Physics has created and directly controlled hybrid electron-photon quantum states in helium atoms. Their findings were published in the journal Nature.
Aerial photo of the research center. Image Credit: Elettra Sincrotrone Trieste.
To achieve this, the team used the FERMI free electron laser in Trieste, Italy, to generate specially prepared, extremely intense extreme ultraviolet light pulses. They then used a novel laser pulse-shaping technique to control the hybrid quantum states.
Strong Light Fields can Create New Quantum States
Electrons can only possess specific energy levels while bound to an atom, and these energy values are primarily determined by the atoms themselves. However, if an atom is exposed to a very strong laser beam, its energy levels can change, leading to the creation of "dressed states" or hybrid electron-photon states.
These states occur at laser intensities ranging from 10 to 100 trillion watts per square centimeter. To produce and control these unique quantum states, laser pulses must reach these intensities within a brief window of just a few trillionths of a second.
Free Electron Laser for Producing Laser Radiation in the Extreme Ultraviolet Range
The researchers used the FERMI free electron laser,
which generates extremely intense laser light in the extreme ultraviolet spectrum. With a wavelength of less than 100 nm, this intense UV radiation is essential for altering the electron states in helium atoms.
To control the electron-photon states, the researchers employed laser pulses that either dispersed or contracted, depending on the situation. They achieved this by adjusting the time delay between the different color components of the laser radiation. A "seed laser pulse" was used to precondition the emission from the free electron laser, allowing the researchers to control the characteristics of the laser pulses.
Our research enabled us for the first time to directly control these transient quantum states in a helium atom. The technique we have developed opens up a new field of research: this includes new opportunities for making experiments with free electron lasers more efficient and selective or for gaining new insights into fundamental quantum systems, which are not accessible with visible light. In particular, it may now be possible to develop methods to study or even control chemical reactions with atomic precision.
Dr. Lukas Bruder, Junior Research Group Leader, Institute of Physics, University of Freiburg
The research received funding from various sources, including the Federal Ministry of Education and Research (BMBF) through the LoKo-FEL (05K16VFB) and STAR (05K19VF3) programs, the European Research Council (ERC) Starting Grant MULTIPLEX (101078689), the German Research Foundation (DFG) via RTG 2717, Grant 429805582 (project SA 3470/4-1), and project STI 125/24-1, as well as the Baden-Württemberg Foundation's elite postdoc program.
Journal Reference:
Richter, F., et al. (2024) Strong-field quantum control in the extreme ultraviolet domain using pulse shaping. Nature. doi.org/10.1038/s41586-024-08209-y.