  A practical source of high fidelity entangled photons is desirable for
quantum information applications and exploring quantum physics. Semiconductor
quantum dots have recently been shown to conveniently emit entangled light when
driven electrically, however the fidelity was not optimal. Here we show that
the fidelity is not limited by decoherence, but by coherent interaction with
nuclei. Furthermore we predict that on 100\mu s timescales, strongly enhanced
fidelities could be achieved. This insight could allow tailoring of quantum
logic to operate using quantum dots in the fault tolerant regime.
