  Many of the envisioned quantum photonic technologies, e.g. a quantum
repeater, rely on an energy- (wavelength-) tunable source of polarization
entangled photon pairs. The energy tunability is a fundamental requirement to
perform two-photon-interference between different sources and to swap the
entanglement. Parametric-down-conversion and four-wave-mixing sources of
entangled photons have shown energy tunability, however the probabilistic
nature of the sources limits their applications in complex quantum protocols.
Here we report a silicon-based hybrid photonic chip where energy-tunable
polarization entangled photons are generated by deterministic and scalable
III-V quantum light sources. This device is based on a micro-electromechanical
system (MEMS) incorporating InAs/GaAs quantum dots (QDs) on a PMNPT-on-silicon
substrate. The entangled photon emissions from single QDs can be tuned by more
than 3000 times of the radiative linewidth without spoiling the entanglement.
With a footprint of several hundred microns, our design facilitates the
miniaturization and scalable integration of indistinguishable entangled photon
sources on silicon. When interfaced with silicon-based quantum photonic
circuits, this device will offer a vast range of exciting possibilities.
