A promising technology for quantum information processing?
For implementing ambitious quantum information processing schemes, such as quantum repeaters, you need a bright photon source that combines high-fidelity entanglement, on-demand generation, high extraction efficiency, directional and coherent emission, as well as position control at the nanoscale. So far all of these properties have yet to be achieved in a single device.
Semiconductor quantum dots embedded in nanowire waveguides look like a promising candidate. This is because the high refractive index of a nanowire waveguide around a quantum dot ensures that the emitted light is guided in the desired direction and a tapered end makes the light extraction very efficient. However, entanglement has not yet been demonstrated for a nanowire quantum dot - until now.
Scientists from Delft University of Technology, the National Research Council of Canada, Politecnico di Milano, and Micro Photon Devices have shown a bright and coherent source of strongly entangled photon pairs from a position-controlled nanowire quantum dot with a fidelity as high as 0.859Â±0.006 and concurrence of 0.80Â±0.02. The InP nanowires contained single InAsP quantum dots and were grown using chemical beam epitaxy.
The report published in Nature Communications, also shows how the two-photon quantum state is modified via the nanowire shape.
The researchers say that the new nanoscale entangled photon source can be integrated at desired positions in a quantum photonic circuit, single-electron devices and light-emitting diodes.
"˜Observation of strongly entangled photon pairs from a nanowire quantum dot' by Marijn A. M. Versteegh et al appears in Nature Communications 5, Article number: 5298 doi:10.1038/ncomms6298