Fig. 1: Numerical time evolution of a free electron in quantum fields.

a–c Electron density \({\rho }_{x,{x}}^{\left(e\right)}\left(t\right)\) for an electron coupled to (a) quantized electromagnetic vacuum (b) a coherent state (c) a single mode of squeezed vacuum. d Wave packet width as a function of time for the three cases plotted in (a–c). e time dependent expectation value of the kinetic energy. The time averaged energy (gray, dashed line) matches the analytically derived ponderomotive energy (pink, solid line)