Efficient detection of multidimensional single-photon time-bin superpositions

The ability to detect quantum superpositions lies at the heart of fundamental and applied aspects of quantum mechanics. The time-frequency degree of freedom of light enables encoding and transmitting quantum information in a multidimensional fashion compatible with fiber and integrated platforms. However, the ability to efficiently detect high-dimensional time-bin superpositions, a subset of encodings in the wider time-frequency paradigm, is not yet available. Here we show that multidimensional time-bin superpositions can be detected using a single time-resolved photon detector. Our approach uses off-the-shelf components and is based on the temporal Talbot effect—a time-frequency counterpart of the well-known near field diffraction effect. We provide experimental results and highlight the possible applications in quantum communication, quantum information processing, and time-frequency quantum state tomography.