Detection of Time-Frequency Entangled Photons in 2D Space and Demonstration of its Duality Relation

Abstract

The time-frequency duality of light is the fundamental concept for ultrafast laser science and technologies. Although the 1D Fourier transform connects electric field distributions between time and frequency domains, 1D treatment is insufficient for understanding the behavior of time-frequency entangled photons. Elucidation of the Fourier duality of entangled-photon wave packets is key for further development of quantum photonics in the ultrafast regime; unfortunately, it hasn’t yet been demonstrated. Here we present the duality as it appears in the frequency spectrum and the temporal shape of the entangled- photon wave packet with two-photon coincidence measurements in the time and frequency domains to extract two-photon time-frequency distributions. We also estimate the time-bandwidth product values in 2D time-frequency space to confirm the Fourier-limited conditions of the entangled-photon wave packets and discuss the prospects of ultrafast quantum optics with time-frequency entangled photons.