Terahertz electro-optic modulation of single photons

The manipulation of visible and near-infrared light at the single-photon level plays a key role in quantum communication systems where information is encoded into photonic degrees of freedom. In practical implementations, it is important to achieve this manipulation with high speeds, low loss, and low noise. In this work, we propose the use of terahertz~(THz) electric fields as a pump source for electro-optic modulation of single photons in bulk media. We demonstrate spectral modulations of single photons in the form of frequency translation and bandwidth manipulations as the terahertz field imparts linear and quadratic phases on the photons at various time delays within 1~ps. Our results show frequency translations exceeding 500~GHz at multi-THz modulation speeds and loss levels of $\approx$1~dB, complementing the current state-of-the-art electro-optic modulation techniques limited to speeds up to 100~GHz. The proposed approach leverages recent developments in terahertz generation techniques, introducing new avenues to manipulate non-classical light in an unexplored regime for quantum photonics.