  We propose a scheme for a two-qubit conditional phase gate by quantum Zeno
effect with semiconductor quantum dots. The system consists of two charged dots
and one ancillary dot that can perform Rabi oscillations under a resonant laser
pulse. The quantum Zeno effect is induced by phonon-assisted exciton relaxation
between the ancillary dot and the charged dots, which is equivalent to a
continuous measurement. We solve analytically the master equation and simulate
the dynamics of the system using a realistic set of parameters. In contrast to
standard schemes, larger phonon relaxation rates increase the fidelity of the
operations.
