We realize quantum gates for path qubits with a high-speed, polarization-independent and tunable beam splitter. Two electro-optical modulators act in a Mach-Zehnder interferometer as high-speed phase shifters and rapidly tune its splitting ratio. We test its performance with heralded single photons, observing a polarization-independent interference contrast above 95%. The switching time is about 5.6 ns, and a maximal repetition rate is 2.5 MHz. We demonstrate tunable feed-forward operations of a single-qubit gate of path-encoded qubits and a two-qubit gate via measurement-induced interaction between two photons.
@article{arxiv.1109.1762,
title = {A high-speed tunable beam splitter for feed-forward photonic quantum information processing},
author = {Xiao-song Ma and Stefan Zotter and Nuray Tetik and Angie Qarry and Thomas Jennewein and Anton Zeilinger},
journal= {arXiv preprint arXiv:1109.1762},
year = {2015}
}