We investigate the superradiance of two-level target atoms (TAs) coupled to a photonic waveguide, demonstrating that the scaling of the superradiance strength can be controlled on demand by an ensemble of control atoms (CAs). The scaling with respect to the number of TAs can be lower, higher, or equal to the traditional Dicke superradiance, depending on the relative positioning of the ensembles and the type of CAs (e.g., small or giant). These phenomena are attributed to unconventional atomic correlations. Furthermore, we observe chiral superradiance of the TAs, where the degree of chirality can be enhanced by giant CAs instead of small ones. The effects discussed in this work could be observed in waveguide QED experiments, offering a potential avenue for manipulating superradiance.
Two interacting Rydberg atoms coupled to a waveguide may realize a giant-atom platform that exhibits controllable (phase-dependent) chirality through which the direction of nonreciprocally scattered photons can be switched on demand, e.g., by the geometrical tuning of an external driving field. In our platform, at variance with traditional setups, the chirality arises from a simple optical implementation of the local phase difference between two coupling points of the Rydberg giant atom. When employing two (or more) driving fields, this platform can also be used as a frequency converter with its strongly asymmetric efficiency being significantly enhanced via the chiral couplings. Our Rydberg giant-atom platform is well suited for chiral quantum optics applications and further offers direct scalability for reaching tunable frequency conversion in the optical domain.
Photonic states with large and fixed photon numbers, such as Fock states, enable quantum-enhanced metrology but remain an experimentally elusive resource. A potentially simple, deterministic, and scalable way to generate these states consists of fully exciting
N quantum emitters equally coupled to a common photonic reservoir, which leads to a collective decay known as Dicke superradiance. The emitted
N-photon state turns out to be a highly entangled multimode state, and to characterize its metrological properties in this work we (i) develop theoretical tools to compute the quantum Fisher information of general multimode photonic states, (ii) use it to show that Dicke superradiant photons in one-dimensional waveguides achieve Heisenberg scaling, which can be saturated by a parity measurement, and (iii) study the robustness of these states to experimental limitations in state-of-the-art atom-waveguide QED setups.
Dicke superradiance, a single-mode burst of radiation emitted by an ensemble of two-level atoms, has garnered tremendous attention within the physics community. Its extension to multi-level systems introduces additional degrees of freedom, such as mode-selective control over well-known Dicke superradiant behaviors. However, previous work on the extension to two-mode superradiance in three-level atoms has been largely overlooked for over five decades. In this study, we revisit the two-mode superradiance model for a Λ-type three-level system, where two modes couple to a common excited state and two separate lower levels, offering new insights. For the first time, we obtain exact numerical solutions of the two-mode rate equations for this model. We analyze the temporal evolution of two-mode intensities, superradiance time delays, and quantum noise in the time domain as the number of atoms varies. We believe this work will enable external mode-selective control over superradiance processes—a capability unattainable in the single-mode case.
Waveguide quantum electrodynamics (WQED) offers a powerful framework for controlling light-matter interactions and realizing collective phenomena such as super- and subradiance. In general waveguide settings, the quantum dynamics spans the full Hilbert space, rendering exact theoretical treatments exponentially difficult and currently out of reach, and only a few models have exact, analytical solutions. Motivated by recent experiments, we treat the thermodynamic limit of the number of atoms,
N→∞, while the homogeneous atom-waveguide coupling
β→0 keeping the optical depth
4Nβ fixed. In this limit, a second order mean field method is exact, giving analytical solutions for the statistics of the photons emitted in the waveguide both for chiral and symmetric configurations starting from full inversion. As
N→∞, the emission in freespace approaches that of an independent ensemble. However, until a special time,
≈1.59× the lifetime of a single-atom, we show an exponentially enhanced superradiance in the waveguide as the optical depth increases. After the special time, the emission into the waveguide exhibits subradiance. We also show that the initial shot-to-shot fluctuations in the rate of emission into the waveguide diminish in a chiral system and vanish in a symmetric system as
N approaches
∞. Additionally, the equal-time second-order correlation becomes trivial, showing that finite-size effects are essential to observe the emergence of second-order coherence. Finally, going beyond the thermodynamic limit requires higher order mean field methods. Our results illustrate finite- and infinite-body collective effects in symmetric and symmetry-lacking systems.
The coherent emission of multiple atoms gives rise to superradiance, a cornerstone phenomenon in quantum optics with wide-ranging applications in quantum information processing and precision metrology. Despite its importance, how the superradiant scaling with respect to the number of participating atoms can be effectively controlled remains largely unexplored. In this work, we investigate a cavity-QED system and demonstrate that atom-photon coupling can significantly alter the emission behavior--suppressing the collective superradiant scaling while enhancing the scaling associated with individual atomic emissions. Our study provides a pathway toward controllable collective emission in state-of-the-art experimental platforms.
Superradiant lasers promise continuous, narrow-linewidth coherent emission at the bare atomic transition frequency, enabling frequency references of exceptional precision. Recent experiments have advanced the field, but achieving truly continuous operation remains technically challenging. Here we propose an alternative route to an active optical frequency reference with fewer emitters using all-to-all dipole-dipole interactions mediated by a nanophotonic waveguide. We show that selectively pumping only a sub-ensemble of emitters, rather than the full ensemble, substantially improves emission characteristics. The collective interactions with unpumped emitters provide narrowband frequency selection and establish an effective feedback mechanism analogous to the role of a macroscopic cavity. We find directional superradiant emission with strongly phase-synchronized emitter correlations and a narrow output spectrum close to the bare emitter resonance. Our results demonstrate a strong metrological gain from selective partial pumping of quantum emitters with the second-order intensity correlation
g(2)(0)≃1, indicating reduced equal-time intensity fluctuations, and open a route to waveguide-based optical frequency references using small clock-atom ensembles for chip-scale precision metrology.