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Frontiers in Optics

Quantum State Tomography of Two-Qubit Photonic States with Undetected Photons

Salini Rajeev, Mayukh Lahiri

Published Jan 1, 2024• 0 citations
Publisher

Abstract

We present a novel, quantum interferometric method of performing quantum state tomography of two-qubit photonic mixed states. The method does not require detecting one of the photons and therefore allows covering of wider spectral ranges.
DOI
10.1364/fio.2024.jw4a.21

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Quantum State Tomography (QST) of optical states is typically performed in the photon number degree of freedom, a procedure which is well understood and has been experimentally demonstrated. However, optical states have other degrees of freedom than just photon number, such as the spatial and temporal/spectral ones. Full characterization of photonic states requires state reconstruction in these additional degrees of freedom. In this paper we present a technique for performing QST of single photon states in the spectral degree of freedom. This is of importance, for example, in quantum information processing applications, which typically impose strict requirements on the purity and distinguishability of independently produced single photons. The described technique allows for full reconstruction of the spectral density matrix, allowing the purity and distinguishability of different sources to be readily calculated.