Precise control of quantum states with extreme ultraviolet lasers

Precise control of quantum states with extreme ultraviolet lasers
by Robert Schreiber
Berlin, Germany (SPX) Dec 16, 2024

An international research team, led by Dr. Lukas Bruder from the Institute of Physics at the University of Freiburg, has successfully produced and directly controlled hybrid quantum states of electrons and photons in helium atoms. Utilizing the FERMI free electron laser in Trieste, Italy, they generated highly intense extreme ultraviolet (EUV) light pulses and applied a novel laser pulse-shaping technique to achieve this feat. Their findings, published in *Nature*, mark a significant advancement in quantum physics.

New quantum states induced by intense light fields

Electrons bound within atoms can only possess specific energy levels determined by the atomic structure. However, under the influence of highly intense laser beams, these energy levels shift, forming hybrid electron-photon states known as "dressed states." Such states arise at laser intensities of 10 to 100 trillion watts per square centimeter. Achieving and controlling these special quantum states requires laser pulses with such intensities delivered in a timeframe of just a few trillionths of a second.

Advanced EUV lasers enable quantum state manipulation

The FERMI free electron laser was instrumental in this research, producing EUV laser light with wavelengths shorter than 100 nanometers. This extreme wavelength was crucial for manipulating the electron states within helium atoms. The researchers employed tailored laser pulses that could be dispersed or compressed, adjusting the time delay of different color components of the radiation. These properties were controlled by a "seed laser pulse" that preconditioned the emission of the FERMI laser.

Dr. Bruder explained the impact of their work: "Our research enabled us for the first time to directly control these transient quantum states in a helium atom. The technique we've 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."

Future potential

This breakthrough technique paves the way for advanced experiments using free electron lasers, providing new tools to explore quantum systems at a level of detail not previously possible. The ability to precisely control these hybrid states could also lead to innovations in studying and influencing chemical reactions with extraordinary precision.

Research Report:Strong-field quantum control in the extreme ultraviolet using pulse shaping