Integrated photonic technologies applied to quantum optics have recently enabled a wealth of breakthrough experiments in several quantum information areas. Path encoding was initially used to demonstrate operations on single or multiple qubits. However, a polarization encoding approach is often simpler and more effective. Two-qubits integrated logic gates as well as complex interferometric structures have been successfully demonstrated exploiting polarization encoding in femtosecond-laser-written photonic circuits. Still, integrated devices performing single-qubit rotations are missing. Here we demonstrate waveguide-based waveplates, fabricated by femtosecond laser pulses, capable to effectively produce arbitrary single-qubit operations in the polarization encoding. By exploiting these novel components we fabricate and test a compact device for the quantum state tomography of two polarization-entangled photons. The integrated optical waveplates complete the toolbox required for a full manipulation of polarization-encoded qubits on-chip, disclosing new scenarios for integrated quantum computation, sensing and simulation, and possibly finding application also in standard photonic devices.
@article{arxiv.1307.7541,
title = {Integrated optical waveplates for arbitrary operations on polarization-encoded single-qubits},
author = {Giacomo Corrielli and Andrea Crespi and Roberto Osellame and Riccardo Geremia and Roberta Ramponi and Linda Sansoni and Andrea Santinelli and Paolo Mataloni and Fabio Sciarrino},
journal= {arXiv preprint arXiv:1307.7541},
year = {2014}
}