Quantum-polarization state tomography

TL;DR

This paper introduces a practical method for quantum-state tomography of multi-photon polarization states, using a fixed setup that reduces systematic errors and enables flexible, adaptive measurements.

Contribution

The authors develop a nondeterministic photon distribution technique for efficient quantum-state tomography of multi-photon polarization states with a fixed measurement setup.

Findings

Successfully demonstrated tomography for N-photon states

Fixed setup eliminates systematic measurement errors

Allows easy switching for adaptive tomography

Abstract

We propose and demonstrate a method for quantum-state tomography of qudits encoded in the quantum polarization of $N$-photon states. This is achieved by distributing $N$ photons nondeterministically into three paths and their subsequent projection, which for $N=1$ is equivalent to measuring the Stokes (or Pauli) operators. The statistics of the recorded $N$-fold coincidences determines the unknown $N$-photon polarization state uniquely. The proposed, fixed setup manifestly rules out any systematic measurement errors due to moving components and allows for simple switching between tomography of different states, which makes it ideal for adaptive tomography schemes.