Evading Vacuum Noise: Wigner Projections or Husimi Samples?

TL;DR

This paper compares homodyne and heterodyne detection methods in quantum state measurement, showing that heterodyne detection generally provides more accurate state reconstruction for Gaussian states under various conditions.

Contribution

It provides experimental evidence that heterodyne detection outperforms homodyne detection for most Gaussian states, highlighting the impact of squeezing and thermal noise.

Findings

Heterodyne detection generally yields more accurate quantum state reconstruction.

Performance depends on squeezing strength and thermal noise levels.

Experimental validation across different Gaussian states.

Abstract

The accuracy in determining the quantum state of a system depends on the type of measurement performed. Homodyne and heterodyne detection are the two main schemes in continuous-variable quantum information. The former leads to a direct reconstruction of the Wigner function of the state, whereas the latter samples its Husimi $Q$~function. We experimentally demonstrate that heterodyne detection outperforms homodyne detection for almost all Gaussian states, the details of which depend on the squeezing strength and thermal noise.