Ramsey-type phase control of free-electron beams

By K. Echternkamp, A. Feist, S. Schafer, C. Ropers. Nature Physics, 2016

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Using a technique inspired by Ramsey spectroscopy it is now possible to coherently control free electrons in an electron microscope. Quantum coherent evolution, interference between multiple distinct paths1,2,3,4 and phase-controlled sequential interactions are the basis for powerful multi-dimensional optical5 and nuclear magnetic resonance3 spectroscopies, including Ramsey’s method of separated fields6. Recent developments in the quantum state preparation of free electrons7 suggest a transfer of such concepts to ultrafast electron imaging and spectroscopy. Here, we demonstrate the sequential coherent manipulation of free-electron superposition states in an ultrashort electron pulse, using nanostructures featuring two spatially separated near-fields with polarization anisotropy. The incident light polarization controls the relative phase of these near-fields, yielding constructive and destructive quantum interference of the subsequent interactions. Future implementations of such electron–light interferometers may provide access to optically phase-resolved electronic dynamics and dephasing mechanisms with attosecond precision.

Subfields: Atomic and Molecular Physics, and Optics, Structural Biology

View Paper: https://www.semanticscholar.org/paper/a4ac2a062171aec0f7a0014b776ce12afc07ed0c