We propose a technique for performing quantum state tomography of photonic polarization-encoded multi-qubit states. Our method uses a single rotating wave plate, a polarizing beam splitter and two photon-counting detectors per photon mode. As the wave plate rotates, the photon counters measure a pseudo-continuous signal which is then Fourier transformed. The density matrix of the state is reconstructed using the relationship between the Fourier coefficients of the signal and the Stokes' parameters that represent the state. The experimental complexity, i.e. different wave plate rotation frequencies, scales linearly with the number of qubits.
@article{arxiv.1211.1399,
title = {Fourier Transform Quantum State Tomography},
author = {Mohammadreza Mohammadi and Agata M. Branczyk and Daniel F. V. James},
journal= {arXiv preprint arXiv:1211.1399},
year = {2013}
}