Direct measurement of ultrafast temporal wavefunctions

TL;DR

This paper introduces a novel, direct method for measuring the complex temporal wavefunctions of single-photon-level light with subpicosecond resolution, eliminating the need for external references or complex processing.

Contribution

The authors demonstrate a new ultrafast measurement technique for temporal quantum states that is simple, versatile, and highly precise, advancing quantum information processing capabilities.

Findings

Achieved subpicosecond time resolution in wavefunction measurement

No external reference light or complex post-processing needed

Applicable to weak light at the single-photon level

Abstract

The large capacity and robustness of information encoding in the temporal mode of photons is important in quantum information processing, in which characterizing temporal quantum states with high usability and time resolution is essential. We propose and demonstrate a direct measurement method of temporal complex wavefunctions for weak light at a single-photon level with subpicosecond time resolution. Our direct measurement is realized by ultrafast metrology of the interference between the light under test and self-generated monochromatic reference light; no external reference light or complicated post-processing algorithms are required. Hence, this method is versatile and potentially widely applicable for temporal state characterization.