  Measurement-based quantum communication relies on the availability of highly
entangled multi-photon cluster states. The inbuilt redundancy in the cluster
allows communication between remote nodes using repeated local measurements,
compensating for photon losses and probabilistic Bell-measurements. For
feasible applications, the cluster generation should be fast, deterministic,
and its photons - indistinguishable. We present a novel source based on a
semiconductor quantum-dot device. The dot confines a heavy-hole, precessing in
a finely tuned external weak magnetic field while periodically excited by a
sequence of optical pulses. Consequently, the dot emits indistinguishable
polarization-entangled photons, where the field strength optimizes the
entanglement. We demonstrate Gigahertz rate deterministic generation of >90%
indistinguishable photons in a cluster state with more than 10 photons
characteristic entanglement-length.
