Phys.org  June 19, 2023 Researchers in Germany used nonlinear-optical two-photon transitions for the quantum-coherent control of a free-electron matter wave in free space. They superimposed an electron beam with two crossed laser beams of different photon energies for non-linear Compton scattering. At suitable angle combinations, the electron energy spectrum became modulated into discrete energy sidebands with thousands of interference maxima. They explained their observations by the cascaded addition and subtraction of two-photon pairs under three-body conservation of energy and momentum. Calculations revealed that the electron matter wave converted into pulses of few-attosecond duration. According to the researchers their work provides […]