Spatio-temporal shaping of a free-electron wave function via coherent light–electron interaction

Abstract

The past decade has witnessed a quantum revolution in the field of computation, communication and materials investigation. A similar revolution is also occurring for free-electron based techniques, where the classical treatment of a free electron as a point particle is being surpassed toward a deeper exploitation of its quantum nature. Adopting familiar concepts from quantum optics, several groups have demonstrated temporal and spatial shaping of a free-electron wave function, developing theoretical descriptions of light-modulated states, as well as predicting and confirming fascinating phenomena as attosecond self-compression and orbital angular momentum transfer from light to electrons. In this review, we revisit the milestones of this development and the several methods adopted for imprinting a time-varying phase modulation on an electron wave function using properly synthesized ultrafast light fields, making the electron an exquisitely selective probe of out-of-equilibrium phenomena in individual atomic/nanoscale systems. We discuss both longitudinal and transverse phase manipulation of free-electrons, where coherent quantized exchanges of energy, linear momentum and orbital angular momentum mediating the electron–light coupling are key in determining their spatio-temporal redistribution. Spatio-temporal phase shaping of matter waves provides new routes toward image-resolution enhancement, selective probing, dynamic control of materials, new quantum information methods, and exploration of electronic motions and nuclear phenomena. Emerging as a new field, electron wave function shaping allows adopting familiar quantum optics concepts in composite-particle experiments and paves the way for atomic, ionic and nuclear wave function engineering with perspective applications in atomic interferometry and direct control of nuclear processes.

Imprinting the quantum statistics of photons on free electrons

“…Last but not least, over the last decade, coherent shaping of spatial electron wavefunctions (42,(72)(73)(74)(75)(76) has opened new avenues in electron microscopy such as electron magnetic circular dichroism (73) and aberration corrections (77). More recently, coherent temporal modulation of electron wavefunctions (13,18,46,63,(78)(79) has excited new ideas for ultrafast light-matter interactions and free-electron coherent control (18,19,80). Especially interesting are the applications of modulation by CW light, showing better phase contrast (43), PINEM by electron post-selection (44), plasmon excitation mapping (45), and advances toward attosecond-resolution metrology (46).…”

Nuclear Excitation by Electron Capture in Excited Ions

“…This could also reveal a way to enhance the electron capture in the innermost shells. The presence of this additional degree of freedom, compared to the solely free electron energy, could open to the possibility of an external control of the NEEC rate in a plasma scenario: by providing pulsed vortex electrons at the resonant energy, the isomer depletion rate can be controlled by dynamically varying the OAM of the vortex beam [54,57,58].…”

Nuclear Excitation by Muon Capture

“…Planned upgrades would make it feasible in the next years to have fluxes up to 10 8 and 10 9 muons per second, resulting approximately in ten to one thousand nuclear excitation per second. Futhermore, an increase in the excitation cross section is expected if the wavefunction of the muon is engineered [39], i.e. considering muon vortex beams [40], as recently suggested for NEEC [8,29,41].…”