Circularly polarized light (CPL) is currently receiving much attention as a
key ingredient for next-generation information technologies, such as quantum
communication and encryption. CPL photon generation for such applications is
commonly realized by coupling achiral optical quantum emitters to chiral
nanoantennas. Here, we explore a different strategy consisting in exciting a
nanosphere -- the ultimate symmetric structure -- to produce all-directional
CPL emission. Specifically, we demonstrate chiral emission from a silicon
nanosphere induced by an electron beam based on two different strategies:
dissolving the degeneracy of orthogonal dipole modes, and interference of
electric and magnetic modes. We prove these concepts by visualizing the phase
and polarization using a newly developed polarimetric four-dimensional
cathodoluminescence method. Besides their fundamental interest, our results
support the use of free-electron-induced light emission from spherically
symmetric systems as a versatile platform for the generation of chiral light
with on-demand control over the phase and degree of polarization