Analogous to Coulomb blockade for electrons, photon blockade is a key quantum optical effect in which the presence of one photon prevents the transmission of subsequent ones through a nonlinear medium. Beyond its fundamental interest, photon and multi-photon blockade are actively studied as mechanisms for generating technologically-relevant quantum states of light. Although photon blockade typically requires achieving strong light-matter coupling, increasing the number of atoms fails to enhance antibunching. Here, we analyze the optical transmission properties of a quantum resonator that embeds a two-photon-coupled ensemble of emitters, combining an approximate analytical approach with full quantum numerical simulations. We show that when light and matter are coupled via a two-photon interaction, both single- and multi-photon blockade can benefit from a collective enhancement. We propose different driving schemes in which the second or third-order correlation functions are strongly suppressed with increasing atom number. Differently from established methods, this collective enhancement of non-classical properties occurs with unitary transmission and is ultimately constrained only by decoherence. This demonstrates that collective two-photon couplings are a powerful mechanism for realizing photon blockade even in platforms where individual strong coupling is not achievable.
Analogous to Coulomb blockade for electrons, photon blockade is a key quantum optical effect in which the presence of one photon prevents the transmission of subsequent ones through a nonlinear medium. Beyond its fundamental interest, photon and multi-photon blockade are actively studied as mechanisms for generating technologically-relevant quantum states of light. Although photon blockade typically requires achieving strong light-matter coupling, increasing the number of atoms fails to enhance antibunching. Here, we analyze the optical transmission properties of a quantum resonator that embeds a two-photon-coupled ensemble of emitters, combining an approximate analytical approach with full quantum numerical simulations. We show that when light and matter are coupled via a two-photon interaction, both single- and multi-photon blockade can benefit from a collective enhancement. We propose different driving schemes in which the second or third-order correlation functions are strongly suppressed with increasing atom number. Differently from established methods, this collective enhancement of non-classical properties occurs with unitary transmission and is ultimately constrained only by decoherence. This demonstrates that collective two-photon couplings are a powerful mechanism for realizing photon blockade even in platforms where individual strong coupling is not achievable.
Photon blockade, in analogy to Coulomb's or phonon blockades, is a phenomenon when a single photon in a nonlinear cavity blocks the transmission of a second photon. This effect can occur in Kerr-type systems driven by a laser due to strong nonlinear photon-photon interactions. We predict the occurrence of higher-order photon blockades where the transmission of more than two photons is effectively blocked by single- and two-photon states. This photon blockade can be achieved by tuning the frequency of the laser driving field to be equal to the sum of the Kerr nonlinearity and the cavity resonance frequency. We refer to this phenomenon as two-photon blockade or two-photon state truncation via nonlinear scissors, and can also be interpreted as photon-induced tunneling. We also show that, for a driving-field frequency fulfilling another resonance condition and for higher strengths of the driving field, even a three-photon blockade can occur but less clearly than in the case of single- and two-photon blockades. We demonstrate how various photon blockades can be identified by analyzing photon-number correlations, coherence and entropic properties, Wigner functions, and spectra of squeezing. We show that two- and three-photon blockades can, in principle, be observed in various cavity and circuit quantum electrodynamical systems for which the standard single-photon blockade was observed without the need of using higher-order driving interactions or Kerr media exhibiting higher-order nonlinear susceptibility.
The antibunching effect generated in a cavity containing first a single two-level atomic system and then two identical atoms is explored for off-resonant interactions, in strong- and weak-coupling regimes. The cavity is driven by coherent and squeezed sources. Using the second-order correlation function analytically derived in the weak-excitation regime, we show that squeezed light achieves and improves strong antibunching, leading to a photon blockade. This enhancement is due to a destructive quantum interference mechanism induced by the nonclassical light, creating a supplementary transition pathway. The best effect is obtained for equal frequency detunings in the strong-coupling regime. More interestingly, our investigation reveals that the two-atom-cavity system can further improve the antibunching effect compared to the single-atom cavity. It turns out that the additional couplings appearing in the cavity due to the implementation of the two atoms, combined with the squeezed light, could substantially enhance the photon-blockade effect.
High-purity and bright single-photon sources are important for quantum information processing and precision measurement. We propose a collectively enhanced universal photon-blockade scheme in a multi-emitter two-photon Tavis--Cummings system. Independent coherent drives of the cavity and collective emitter enable destructive interference between two-photon excitation pathways, while collective coupling supplies level anharmonicity. Full-quantum master-equation simulations, the Holstein--Primakoff approximation, and a non-Hermitian probability-amplitude analysis yield the optimal conditions: cavity resonance together with phase and amplitude matching. Compared with a purely collective blockade, the proposed scheme lowers g(2)(0), and essentially preserves the single-photon population. As the emitter number N increases, the optimal point remains at Δc=0, while the minimum correlation follows gmin(2)(0)∝N−2. By contrast, unconventional photon blockade shifts away from resonance as N increases, limiting its purity improvement and brightness. In the weak-drive regime, universal blockade obeys g(2)(0)∝εa2, owing to a higher-order bypass through the three-excitation manifold. The drive strength therefore provides an additional purity--brightness control, although the interference mechanism makes the scheme more sensitive to dissipation-rate mismatch. Our results establish a scalable route to bright, high-purity, and tunable single-photon emission in multi-emitter cavity-QED systems.
Universal photon blockade in a two-mode Jaynes-Cummings model incorporating third-order Kerr nonlinearity is demonstrated with a single two-level atom coupled to a waveguide microcavity. Realization of this universal photon blockade is attributed to the cooperative effects of field-atom coupling and Kerr nonlinearity. More importantly, this antibunching is found to be robust against the atomic spontaneous emission, driving field strength, and defect-induced cavity mode coupling. The strong antibunching effect in this resonance-driven scheme is essentially different from those without Kerr nonlinearity. Moreover, this work expands the platform for achieving universal photon blockade and reveals the cooperative advantages of nonlinearities in enhancing the purity and brightness of single-photon sources, representing a novel strategy toward high-performance single-photon sources in integrated quantum optical devices.
Photon blockade (PB) is generally classified into conventional and unconventional types based on their distinct physical mechanisms. Recent studies have aimed to bridge the two regimes to realize a universal photon blockade (universal PB) that combines their respective advantages. Here, we propose a scheme for achieving universal PB based on second-order nonlinearity. The second-order nonlinear coupling between two cavity modes mediates the fundamental interaction, while an optical parametric amplifier embedded in one cavity introduces additional quantum interference pathways. We analytically derive the optimal conditions for universal PB, and the analytical results show excellent agreement with numerical simulations. By comparing universal PB with conventional PB, we highlight its unique performance advantages: the scheme operates effectively in both strong and weak coupling regimes, relaxes experimental constraints, and achieves an ultra-low equal-time second-order correlation function g (2) (0) down to 10 −7 , while maintaining a moderate mean photon number N a ∼ 10 −2 . This work provides a feasible and tunable platform for realizing high-purity single-photon sources and exploring quantum statistical properties in nonlinear cavity systems.
The photon blockade (PB) effect represents a quintessential manifestation of quantum optical nonlinearity, where the presence of a single photon within an optical cavity prevents the entry of a second one, thereby realizing a single-photon source. This effect underpins numerous applications in quantum information processing, secure communication, and quantum computation. Nevertheless, the intrinsic nonlinearity of practical optical systems is often too weak to produce a strong blockade, making the enhancement and controllability of the PB effect a persistent challenge. To overcome this limitation, we investigate a two-cavity quantum system incorporating two-photon dissipation as an alternative mechanism for realizing photon blockade. In contrast to conventional schemes that primarily consider single-photon loss, the proposed configuration introduces a second-order nonlinear dissipation channel, through which the correlated loss of photon pairs fundamentally modifies the photon statistics and strengthens the blockade effect. Based on quantum master equation theory, we constructed a model of a two-cavity system incorporating two-photon dissipation and analyzed the effect of different parameters on the photon blockade effect through numerical simulations.