Observation of Rabi dynamics with a short-wavelength free-electron laser.

Area of Science:

• Atomic, Molecular, and Optical Physics
• Quantum Optics
• Ultrafast Science

Background:

• Rabi oscillations describe population dynamics in two-level systems interacting with time-varying fields.
• These oscillations have broad applications in photonics, nano-electronics, electron microscopy, and quantum information.
• While theory exists for coherent light-matter interactions, Rabi dynamics at extreme-ultraviolet wavelengths remain unobserved.

Purpose of the Study:

• To experimentally observe Rabi dynamics at extreme-ultraviolet wavelengths.
• To investigate coherent atom-field interactions in helium atoms using femtosecond pulses.
• To explore ultrafast manipulation of quantum processes at short wavelengths.

Main Methods:

• Utilized femtosecond extreme-ultraviolet pulses from a seeded free-electron laser.
• Drove Rabi dynamics between the ground and excited states in helium atoms.
• Measured photoelectron signals to analyze atomic response.

Main Results:

• Successfully observed Rabi dynamics in helium atoms at extreme-ultraviolet wavelengths.
• Detected Autler-Townes doublet and avoided crossing, confirming coherent atom-field interactions.
• Identified quantum interference between resonant and non-resonant photoionization pathways.

Conclusions:

• Demonstrated the feasibility of driving Rabi dynamics with intense ultrashort extreme-ultraviolet pulses.
• The findings provide insights into quantum interference effects in atom-field interactions.
• Unveiled opportunities for ultrafast coherent control at short wavelengths using free-electron lasers.