Superresolving multiphoton interferences with independent light sources
Physical Review Letters 109, 233603 (2012)
Multiphoton interferences with indistinguishable photons from independent light sources are at the focus of current research owing to their potential in optical quantum computing, creating remote entanglement for quantum computation and communication, and quantum metrology. The paradigmatic states for multi-photon interference are the highly entangled NOON states, which can be used to achieve increased resolution in spectroscopy, interferometry, lithography, and microscopy. Multi-photon interferences from independent, uncorrelated emitters can also lead to enhanced resolution in metrology and imaging. So far, such interferences have been observed with maximally two independent emitters. Here, we report multi-photon interferences with up to five independent emitters, displaying interference patterns equivalent to those of NOON states. Experimental results with independent thermal light sources confirm this NOON-like modulation. The experiment is an extension of the landmark measurement by Hanbury Brown and Twiss who investigated intensity correlations of second order. Here we go beyond this level by measuring spatial intensity correlations up to fifth order to further increase the resolution. The inherent simplicity of our scheme opens up the possibility of improved imaging in astronomy and biology.