%0 Journal Article
%A Donohue, J. M.
%A Ansari, V.
%A Řeháček, Jaroslav
%A Hradil, Zdenek
%A Stoklasa, Bohumil
%A Paúr, Martin
%A Sánchez Soto, Luis Lorenzo
%A Silberhorn, C.
%T Quantum-limited time-frequency estimation through mode-selective photon measurement
%D 2018
%@ 0031-9007
%U https://hdl.handle.net/20.500.14352/12251
%X By projecting onto complex optical mode profiles, it is possible to estimate arbitrarily small separations between objects with quantum-limited precision, free of uncertainty arising from overlapping intensity profiles. Here we extend these techniques to the time-frequency domain using mode-selective sum-frequency generation with shaped ultrafast pulses. We experimentally resolve temporal and spectral separations between incoherent mixtures of single-photon level signals ten times smaller than their optical bandwidths with a tenfold improvement in precision over the intensity-only Cramer-Rao bound.
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