Single-photon pulses cannot be generated on demand, due to incompatible requirements of positive frequencies and times. Resulting states therefore contain small probabilities for multiphotons. We derive upper lower bounds the maximum fidelity realizable that approximate single-photon pulses. The have implications ultrafast optics; is low with few cycles or close onset, but increases rapidly as ...

Chiral photons have the potential to advance information technologies due their robustness in carrying binary data against noisy backgrounds as well capacity for constructing single-photon isolators and circulators through nonreciprocal photon propagation. In this Perspective, we highlight recent efforts generate chiral single using circularly polarized light sources. We delve into possible fut...

We present the theoretical rationales for data analysis protocols that afford an efficient extraction of conformational dynamics on a broad range of time scales from single-molecule fluorescence lifetime trajectories. Based on correlation analyses, a photon-by-photon approach on one hand provides the highest time resolution, whereas a minimal-binning method on the other hand is most suitable fo...

We experimentally investigated the intensity cross-correlation between the upconverted photons and the unconverted photons in the single-photon frequency upconversion process with multi-longitudinal mode pump and signal sources. In theoretical analysis, with this multi-longitudinal mode of both signal and pump sources system, the properties of the signal photons could also be maintained as in t...

Engineering light at the single photon level is a long-standing goal in physics. In this thesis, we investigate optical nonlinearities at the single photon level orchestrated by an optical cavity. We demonstrate an all-optical transistor where one stored ‘gate’ photon controls the propagation of a ’source’ light beam. The system is based on EIT and a highcooperativity cavity. Each ’gate’ photon...