Hyperradiance accompanied by nonclassicality

Several recent experiments have reported a variety of new collective behaviors of two atoms in a cavity. An important experimental result was that the back-reaction in a high-quality cavity leads to subradiance rather than superradiance. Further investigation by changing the parameter domain has shown the possibility of hyperradiance. In this paper we present a model of hyperradiance which is based on the idea of vacuum Rabi splittings when the driving field is detuned from the atom or cavity resonance so that it hits one of the dressed states. We show that this hyperradiance is accompanied by significant nonclassicality of the output. Some aspects, but not nonclassicality, of the hyperradiance when the driving field is very weak can be understood semiclassically. Our mechanism of hyperradiance applies to atoms coupled symmetrically to the cavity mode, whereas in the work of M. Pleinert et al. [Optica 4, 779 (2017)] atoms have to be coupled almost asymmetrically to the cavity.

Figure 1

Coherently driven two-atom CQED system in which two identical two-level atoms are coupled to the cavity mode and driven by a coherent field with Rabi frequency $\eta$.

Figure 2

The energy scheme of the atom-cavity dressed system. (a) Single atom in the cavity and (b) two atoms in the cavity.

Figure 3

(a) Average number $\langle a^{+}a\rangle$ of photons in the cavity, (b) witness $R$, and (c) the second-order correlation $g^{\left(2\right)}\left(0\right)$ as function of detuning ${\delta }_{\mathrm{A}}$ and coupling $g$ under constant excitation of two in-phase atoms in the cavity. The system parameters are $\eta =0.5\kappa ,\gamma =3\kappa$. The white dashed lines refer to ${\delta }_A=\sqrt{2}g$, while the white dot-dashed line refers to ${\delta }_A=g$. The thick black curve in (b) [(c)] refers to the contour of $R=1\left[g^{\left(2\right)}\right(0)=1]$.

Figure 4

(a) Average number $\langle a^{+}a\rangle$ of photons in the cavity, (b) witness $R$, and (c) the second-order correlation $g^{\left(2\right)}\left(0\right)$ as a function of detuning ${\delta }_{\mathrm{A}}$ and coupling $g$ under constant excitation of two in-phase atoms in the cavity. The system parameters are $\eta =3\kappa ,\gamma =3\kappa$. The white dashed lines refer to ${\delta }_A=\sqrt{2}g$, while the white dot-dashed line refers to ${\delta }_A=g$. The thick black curve in (b) [(c)] refers to the contour of $R=1\left[g^{\left(2\right)}\right(0)=1]$.

Figure 5

(a) Average number $\langle a^{+}a\rangle$ of photons in the cavity, (b) witness $R$, and (c) the second-order correlation $g^{\left(2\right)}\left(0\right)$ as a function of detuning ${\delta }_{\mathrm{A}}$ and Rabi frequency $\eta$ of the driving field on two in-phase atoms in the cavity. The system parameters are $g=5\kappa$ and $\gamma =3\kappa$.The thick black curve in (b) [(c)] refers to the contour of $R=1\left[g^{\left(2\right)}\right(0)=1]$.

Figure 6

The results from the semiclassical theory. (a) Cavity field with a single atom in the cavity, (b) cavity field with two atoms in the cavity, (c) witness $R$ as a function of detuning ${\delta }_A={\omega }_a-{\omega }_l$ and coupling $g$. The system parameters are $\eta =0.5\kappa$ and $\gamma =3\kappa$. The white dashed line refers to ${\delta }_A=\sqrt{2}g$, while the white dot-dashed line refers to ${\delta }_A=g$. The thick black curve in (c) refers to the contour of $R=1$.