Dicke superradiance and Hanbury Brown and Twiss intensity interference: two sides of the same coin

SPICE Workshop on Quantum Spinoptics, June 13th - 15th 2023

Joachim von Zanthier

Superradiance is one of the enigmatic problems in quantum optics since Dicke introduced the concept of enhanced spontaneous emission by an ensemble of identical two-level atoms, situated in collective highly entangled Dicke states [1]. While single excited Dicke states have been investigated since a long time, the production of Dicke states with higher number of excitations remains a challenge. In our approach, we generate these states via successive measurement of photons at particular positions starting from the fully excited system. In this case, if the detection is unable to identify the individual photon source, the collective system cascades down the ladder of symmetric Dicke states each time a photon is recorded. This is another example of measurement induced entanglement among parties which do not directly interact with each other [2–9]. Detecting m photons scattered from m < N atoms amounts to measuring the m-th order photon correlation function. Measuring this function allows (a) the production of any symmetric Dicke state from initially uncorrelated atoms and (b) the observation of superradiant emission patterns of the resultant Dicke states [10,11]. We apply this scheme to demonstrate directional super- and subradiance with two trapped ions [12]. The arrangement for measuring the higher order photon correlation functions corresponds to a generalized Hanbury Brown and Twiss setup. This demonstrates that the two fundamental phenomena of quantum optics, Dicke superradiance and the Hanbury Brown and Twiss effect, are two sides of the same coin.

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