Fig. 1

Superradiance from nanodiamonds with many NV centres. a Graphic representation of cooperatively interacting NV centres emitting a superradiant burst from a nanoscale diamond crystal. The zoom-in shows the underlying crystalline structure around a single NV centre, with the substitutional nitrogen atom indicated in green and the vacancy in white. It also displays the level structure of a single NV centre in bulk diamond¹¹. Due to strong vibronic sidebands, only a fraction of photons is emitted into the ZPL. In our high-density NV ND sample the ZPL is shifted from the bulk value of 637 nm, as seen in the representative fluorescence spectrum with a ZPL of around 639 nm¹². b Measured normalised fluorescence decay curves for five different NDs, with lifetimes ranging from the usual few tens of nanoseconds for a single NV centre in a ND (red trace), to around 1 ns for high-density NV NDs (green trace, ND #4). c Illustration of the Dicke ladder of states: Collective optical decay couples descending states within each pseudospin J-subspace at a characteristic rate γ _{J , M} . Local dephasing at rate γ _d decouples individual spins from the collective subspace, leaving the remaining spins in a smaller J-subspace. Thicker/darker decay lines denote stronger decay rates with maximum decay near M = 0 states