Direct measurement of the biphoton Wigner function through two-photon interference

Area of Science:

• Quantum Optics
• Quantum Information Science

Background:

• The Hong-Ou-Mandel (HOM) experiment is foundational in quantum optics, demonstrating photon pair non-classicality.
• The HOM experiment has been extended to systems with bosonic or fermionic statistics.

Purpose of the Study:

• To demonstrate a direct measurement of the Wigner function using a modified HOM experiment.
• To explore the implications of Wigner function measurements for characterizing quantum entanglement.

Main Methods:

• Modification of the standard Hong-Ou-Mandel experimental setup.
• Application of the modified setup to biphotons generated via spontaneous parametric down-conversion.
• Analysis of the Wigner function for inferring entanglement properties.

Main Results:

• A simple modification to the HOM experiment enables direct Wigner function measurement.
• Negative Wigner function values are shown to be a sufficient condition for non-Gaussian entanglement between two photons.
• The Wigner function provides complete information for entanglement criteria.

Conclusions:

• The modified HOM experiment offers a novel approach for quantum state characterization.
• This method enhances the utility of the HOM experiment for fundamental quantum mechanics tests.
• The study links Wigner function negativity directly to non-Gaussian entanglement in optical systems.