Perspectives on all-optical Kerr switching for quantum optical applications

Abstract

We offer a perspective on recent advances in picosecond-timescale all-optical switching with applications in quantum optics. The switch is based on polarization rotation in standard single-mode fiber via the optical Kerr effect. By using ultrafast laser pulses and short (∼10 cm) fibers, this technique can achieve a switching duration of ≲1 ps, at the repetition rate of 80 MHz or above. This high repetition rate is well-suited to quantum optics where experiments operate in the photon-counting regime. The switch efficiency can be ≳99% with a noise floor of just ∼10−4 photons/pulse, enabling high fidelity operations on quantum states of light, with negligible generation of spurious noise photons. We highlight the capabilities of this technique in four early applications: switching of heralded single photons, time-bin to polarization conversion of photonic qubits, noise gating for quantum key distribution, and pulse carving.