Preparation and characterization of arbitrary states of four-dimensional qudits based on biphotons

TL;DR

This paper presents interferometric methods to prepare and characterize arbitrary four-dimensional qudit states using biphoton states from ultrafast-pumped spontaneous parametric down-conversion, demonstrating experimental control over various state types.

Contribution

It introduces novel interferometric schemes for the preparation and tomography of arbitrary four-dimensional qudit states based on biphoton systems.

Findings

Successful preparation of various ququart states

Experimental demonstration of state tomography

Validation of the proposed methods

Abstract

We report interferometric schemes to prepare arbitrary states of four-dimensional qudits (ququarts) based on biphoton states of ultrafast-pumped frequency-nondegenerate spontaneous parametric down-conversion. Preparation and tomographic characterization of a few examples of general single-ququart states, a pure state, a completely mixed state, and a partially-mixed state, are experimentally demonstrated.