Coherent Control and Reconstruction of Free-Electron Quantum States in Ultrafast Electron Microscopy
Katharina Elisabeth Priebe
Cumulative thesis
Date of Examination:
2017-12-19
Date of issue:
2018-01-04
Advisor:
Ropers, Claus Prof. Dr.
Referee:
Mathias, Stefan Prof. Dr.
Referee:
Baumert, Thomas Prof. Dr.
Persistent Address: http://hdl.handle.net/11858/00-1735-0000-002E-E30D-2
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Abstract
English
The present (cumulative) thesis examines the quantum coherent interaction of ultrashort free-electron pulses with tailored optical near-fields. Multiple fields are utilised to prepare, coherently manipulate and characterise the longitudinal component of free-electron momentum superposition states. After traversal of an intense optical near-field, the free-electron kinetic energy spectrum exhibits sidebands that are separated by the photon energy, which can be attributed to a phase modulation of the longitudinal electron wavefunction. To characterise these electron quantum states, an algorithm termed "SQUIRRELS" (Spectral QUantum Interference for the Regularised Reconstruction of free-ELectron States) is developed that is capable of reconstructing free-electron density matrices from experimental spectrograms. As a first application, quantum state reconstruction by SQUIRRELS is used to experimentally demonstrate sub-cycle temporal structuring of the electron density. Free-space propagation of the phase-modulated electron wavefunction dispersively reshapes the electron density, leading to the formation of a train of attosecond electron density spikes at few-millimetre distance behind the interaction plane. Inelastic electron-light scattering may thus find application as a programmable, temporal phase plate for free electrons enabling time-resolved electron microscopy with attosecond precision. Besides spatio-temporal shaping of electrons, phase-locked interactions with multiple near-fields constitute an essential building block for future quantum optics experiments with free electrons.
Keywords: quantum state reconstruction; ultrafast transmission electron microscope; free electron quantum state; coherent control; optical phase modulation; quantum optics; optical near-field; attosecond electron pulse train
