Stimulated emission quantum state tomography for frequency non-degenerate entangled photon pairs

TL;DR

This paper demonstrates a stimulated emission tomography method to characterize frequency non-degenerate entangled photon pairs, enabling efficient quantum state measurement at wavelengths where single-photon detectors are ineffective.

Contribution

The study introduces a reliable stimulated emission tomography technique for entangled photons with highly dissimilar frequencies, bypassing the need for wavelength-specific single-photon detectors.

Findings

SET produces results consistent with standard quantum state tomography.

The method is effective for wavelengths where single-photon detectors are unavailable.

Enables characterization of entangled states in IR and THz regimes.

Abstract

Frequency non-degenerate entangled photon pairs have been employed in quantum communication, imaging, and sensing. To characterize quantum entangled state with long-wavelength (infrared, IR or even terahertz, THz) photon, one needs to either develop the single-photon detectors at the corresponding wavelengths or use novel tomography technique, which does not rely on single-photon detections, such as stimulated emission tomography (SET). We use standard quantum state tomography and SET to measure the density matrix of entangled photon pairs, with one photon at 1550 nm and the other one at 810 nm, and obtain highly consistent results, showing the reliability of SET. Our work paves the way for efficient measurement of entangled photons with highly dissimilar frequencies, even to the frequencies where single-photon detections are not available.