  We demonstrate the existence of stable non-dispersing two-electron
Trojan-like wave packets in the helium atom in combined magnetic and circularly
polarized microwave fields. These packets follow circular orbits and we show
that they can also exist in quantum dots. Classically the two electrons follow
trajectories which resemble orbits discovered by Langmuir and which were used
in attempts at a Bohr-like quantization of the helium atom. Eigenvalues of a
generalized Hessian matrix are computed to investigate the classical stability
of these states. Diffusion Monte Carlo simulations demonstrate the quantum
stability of these two-electron wave packets in the helium atom and quantum dot
helium with an impurity center.
