Calculating the statistical characteristics of the superradiance from an ensemble of multilevel molecules

A. Crubellier, Catherine Bréchignac, Ph. Cahuzac +1 more

In the theoretical stuqy of superradiance, the atoms or molecules are generally considered as two-level systems. However in many experimental situations, this simple assumption is not valid. It is the case, for example, in all experiments exhibiting superradiant beats [1-3]. Moreover, these beats are sometimes due to a specific property of superradiance : the existence of interferences between different atoms. Other examples of multilevel superradiance are encountered each time one observes several superradiant transitions sharing a common level [3,4]. In addition, superradiance is generally observed between degenerate levels, and it has been alreaqy shown experimentally that the level-degeneracy influences the properties of the superradiant light, in particular its polarization characteristics [5].

I.M. Lizin, Махвиладзе Тариэль Михайлович, Leonid A. Shelepin

Amir Sivan, Meir Orenstein

We propose realization of sources of multiphoton entanglement from atomic ensembles via a fast and deterministic superradiance process [1]. We leverage the collective emission phenomenon of superradiance in order to generate multiphoton states, and entangle them in their frequency degree of freedom by incorporating the dynamics of multilevel atoms. Such deterministic high-yield sources of entangled photons are crucial for applications pertaining to quantum computation, quantum communications and quantum metrology [2]. We emphasize that the original Dicke superradiance model [3] and its extensions have only dealt with the atomic-ensemble entanglement and photonic ensemble-average observables such as intensity and autocorrelation, and photonic entanglement in superradiance has never been considered.

Igor Ferrier-Barbut

Amir Sivan, Meir Orenstein

We show here that the photonic states emitted by ensembles of multilevel atoms via a superradiance process exhibit entanglement in the modal (frequency) degree of freedom, making this collective emission process a favorable candidate for a fast, bright, and deterministic source of entangled photons. This entanglement is driven by two mechanisms: (i) selective excitation of the atomic ensemble to a superposition state, and (ii) degeneracies of the optical transitions owing to the internal structure of the emitting atoms. The latter induces intricate nonradiative virtual transitions in the ensemble, which create interatomic correlations that are imprinted onto the emitted photons. One of the important outcomes of this complexity is the generation of mode-independent entangled multiphoton states. In addition, we study the dynamics of the correlations of the superradiating multilevel atom ensembles, and demonstrate a case where they exhibit beating in steady state as a result of the aforementioned virtual transitions.

A.V. Andreev, P. V. Polevoy