Two-photon quantum state engineering in nonlinear photonic nanowires

We propose and analyze a generic technique to engineer the two-photon quantum state generated by spontaneous parametric downconversion (SPDC) in nonlinear photonic nanowires using any suitable material system. Through dispersion engineering in nanowires, the group velocity of each photon involved in the SPDC process can be tuned such that pure heralded single photons or maximally polarization entangled photons can be directly generated on a chip. Implementations in III–V semiconductor and ferroelectric waveguides demonstrate minimal frequency correlations with Schmidt numbers of ∼1 for heralded single photons, and maximal entanglement with concur-rences of ∼1 for polarization entangled photons. © 2014 Optical Society of America OCIS codes: (130.3120) Integrated optics devices; (190.4390) Nonlinear optics, integrated optics; (230.4320) Nonlinear optical devices; (270.5585) Quantum information and processing