The working principles of linear optical quantum computing are based on photodetection, namely, projective measurements. The use of photodetection can provide efficient nonlinear interactions between photons at the single-photon level, which is technically problematic otherwise. We report an application of such a technique to prepare quantum correlations as an important resource for Heisenberg-limited optical interferometry, where the sensitivity of phase measurements can be improved beyond the usual shot-noise limit. Furthermore, using such nonlinearities, optical quantum non-demolition measurements can now be carried out easily at the single-photon level.
Publication Source (Journal or Book title)
Journal of Optics B: Quantum and Semiclassical Optics
Lee, H., Kok, P., Williams, C., & Dowling, J. (2004). From linear optical quantum computing to Heisenberg-limited interferometry. Journal of Optics B: Quantum and Semiclassical Optics, 6 (8) https://doi.org/10.1088/1464-4266/6/8/026