  Recent proposals and advances in quantum simulations, quantum cryptography
and quantum communications substantially rely on quantum entanglement
formation. Contrary to the conventional wisdom that dissipation destroys
quantum coherence, coupling with a dissipative environment can also generate
entanglement. We consider a system composed of two quantum dot qubits coupled
with a common, damped surface plasmon mode; each quantum dot is also coupled to
a separate photonic cavity mode. Cavity quantum electrodynamics calculations
show that upon optical excitation by a femtosecond laser pulse, entanglement of
the quantum dot excitons occurs, and the time evolution of the $g^{(2)}$ pair
correlation function of the cavity photons is an indicator of the entanglement.
We also show that the degree of entanglement is conserved during the time
evolution of the system. Furthermore, if coupling of the photonic cavity and
quantum dot modes is large enough, the quantum dot entanglement can be
transferred to the cavity modes to increase the overall entanglement lifetime.
This latter phenomenon can be viewed as a signature of entangled, long-lived
quantum dot exciton-polariton formation. The preservation of total entanglement
in the strong coupling limit of the cavity/quantum dot interactions suggests a
novel means of entanglement storage and manipulation in high-quality optical
cavities.
