  We study theoretically interaction between electrons in a quantum ring
embedded in a microcavity and vacuum fluctuations of electromagnetic field in
the cavity. It is shown that the vacuum fluctuations can split electron states
of the ring with opposite angular momenta. As a consequence, the ground state
of electron system in the quantum ring can be associated to nonzero electric
current. Since a ground-state current flows without dissipation, such a quantum
ring gets a magnetic moment and can be treated as an artificial spin.
