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.

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Wavelength-tunable, time-locked pairs of ultrafast pulses are crucial in modern-day time-resolved measurements. We demonstrate a simple means of generating configurable optical pulse sequences: sub-picosecond pulses are carved out from a continuous wave laser via pump-induced optical Kerr switching in 10 cm of a commercial single-mode fiber. By introducing dispersion to the pump, the near transform-limited switched pulse duration is tuned between 305–570 fs. Two- and four-pulse signal trains are also generated by adding birefringent α-BBO plates in the pump beam. These results highlight an ultrafast light source with intrinsic timing stability and pulse-to-pulse phase coherence, where pulse generation could be adapted to wavelengths ranging from ultraviolet to infrared.