Optimal Coherent Filtering for Single Noisy Photons
Shaobo Gao, O. Lazo-Arjona, Benjamin Brecht, K. T. Kaczmarek, Sarah E. Thomas, Joshua Nunn, Patrick M. Ledingham, D. J. Saunders, Ian A. Walmsley · Physical Review Letters · 2019
We introduce a filter using a noise-free quantum buffer with large optical bandwidth that can both filter temporal-spectral modes as well as interconvert them and change their frequency. We theoretically show that such quantum buffers optimally filter out temporal-spectral noise, producing identical single photons from many distinguishable noisy single-photon sources with the minimum required reduction in brightness. We then experimentally demonstrate a noise-free quantum buffer in a warm atomic system that is well matched to quantum dots. Based on these experiments, simulations show that our buffer can outperform all intensity (incoherent) filtering schemes for increasing indistinguishability.