Effects of coherence on temporal resolution

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De, Syamsundar
Gil López, Jano
Brecht, Benjamin
Silberhorn, Christine
Hradil, Zdeněk
Řeháček, Jaroslav
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American Physical Society
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Measuring small separations between two optical sources, either in space or in time, constitutes an important metrological challenge as standard intensity-only measurements fail for vanishing separations. Contrarily, it has been established that appropriate coherent mode projections can appraise arbitrarily small separations with quantum-limited precision. However, the question of whether the optical coherence brings any metrological advantage to mode projections is still a point of debate. Here, we elucidate this problem by experimentally investigating the effect of varying coherence on estimating the temporal separation between two single-photon pulses. We show that, for an accurate interpretation, special attention must be paid to properly normalize the quantum Fisher information to account for the strength of the signal.
©2021 American Physical Society. We thank V. Ansari and J. M. Donohue for discussions. This work received funding from the European Union’s Horizon 2020 research and innovation programme under grant Agreement No. 899587. This work was supported by the European Union’s Horizon 2020 research and innovation programme under the QuantERA programme through the Project ApresSF. We acknowledge support from the Grant Agency of the Czech Republic (18-04291S) and the Spanish Ministerio de Ciencia e Innovación (PGC2018-099183-B-I00).