  Temporally shaping the density of electron beams using light forms the basis
for a wide range of established and emerging technologies, including
free-electron lasers and attosecond electron microscopy. The modulation depth
of compressed electron pulses is a key figure of merit limiting applications.
In this work, we present an approach for generating background-free attosecond
electron pulse trains by sequential inelastic electron-light scattering.
Harnessing quantum interference in the fractional Talbot effect, we suppress
unwanted background density in electron compression by several orders of
magnitude. Our results will greatly enhance applications of coherent
electron-light scattering, such as stimulated cathodoluminescence and
streaking.
