Plasmonic nanoantennas for efficient control of polarization-entangled photon pairs

We suggest a source of polarization-entangled photon pairs based on a cross-shaped plasmonic nanoantenna driven by a single quantum dot. The integration of the nanoantenna with a metal mirror overcomes the fundamental tradeoff between the spontaneous emission (SE) enhancement and the extraction efficiency typical of microcavity- and nanowire-based architectures. With a very high extraction efficiency of entangled photons (≈90%) at 1.55 μm and large SE enhancement (≈90) over a broad 330-nm spectral range, the proposed design will pave the way toward reliable integrated sources of nonclassical light.