Photon blockade produces antibunched light, but a source also needs a defined output port, nonzero extractable flux, and experimentally accessible controls. We analyze an atom-assisted three-wave-mixing cavity where the driven target mode is monitored directly as the output. A two-level emitter and an auxiliary pair-exchange channel provide coherent paths to the same target-mode Fock states, with their interference controlled by η = (Ω/ F a ) e i Δ ϕ . In the weak-drive limit, canceling the target two-photon amplitude gives high-purity single-photon blockade (1PB), whereas canceling the target three-photon amplitude gives pair-enhanced two-photon blockade (2PB). Full Lindblad calculations yield g a (2) (0)∼10 −4 and P 1 /(1 − P 0 ) > 0.99 over R / κ a = 0.2–5. A representative 2PB point has g a (2) (0)=1.91, g a (3) (0)=1.26×10 −3 , and P n ≥3 / P 2 = 7.55 × 10 −8 . At fixed | η |, changing only the relative phase switches the output from a single-photon-dominated endpoint to a pair-enhanced 2PB endpoint within a few cavity lifetimes. The optimized states remain weakly populated, so the scheme favors purity and reconfigurability over high flux.
Photon blockade produces antibunched light, but a source also needs a defined output port, nonzero extractable flux, and experimentally accessible controls. We analyze an atom-assisted three-wave-mixing cavity where the driven target mode is monitored directly as the output. A two-level emitter and an auxiliary pair-exchange channel provide coherent paths to the same target-mode Fock states, with their interference controlled by η = (Ω/ F a ) e i Δ ϕ . In the weak-drive limit, canceling the target two-photon amplitude gives high-purity single-photon blockade (1PB), whereas canceling the target three-photon amplitude gives pair-enhanced two-photon blockade (2PB). Full Lindblad calculations yield g a (2) (0)∼10 −4 and P 1 /(1 − P 0 ) > 0.99 over R / κ a = 0.2–5. A representative 2PB point has g a (2) (0)=1.91, g a (3) (0)=1.26×10 −3 , and P n ≥3 / P 2 = 7.55 × 10 −8 . At fixed | η |, changing only the relative phase switches the output from a single-photon-dominated endpoint to a pair-enhanced 2PB endpoint within a few cavity lifetimes. The optimized states remain weakly populated, so the scheme favors purity and reconfigurability over high flux.
This paper discusses conventional photon blockade (CPB) and two-photon blockade (2PB) in a three-wave mixing system embedded with a two-level atom in the high-frequency cavity. Analytical conditions for achieving CPB and 2PB are obtained by analyzing the eigenvalues of the system Hamiltonian. Numerical solutions, derived by solving the master equation in a truncated Fock space, are consistent with the analytical conditions. Detailed analysis of system parameters reveals the influence of the embedded atom on achieving different types of photon blockade. Unlike previous schemes, this system can achieve single-photon blockade simultaneously in three photon modes. Additionally, by adjusting the coupling coefficient between the atom and high-frequency mode photons, the system can switch between single-photon blockade and two-photon blockade in the high-frequency mode.
We propose a component-selective scheme for improving two-photon sources in a cavity-coupled two-atom system, where a single cavity mode interacts with two two-level atoms driven by phase-controlled classical fields of the same frequency. By controlling the atomic detunings and driving phase, the system can be tailored toward optimized cavity-field two-photon blockade or strongly correlated fluorescence photon-pair emission. When the two-cavity-photon component is enhanced, the cavity field exhibits optimized two-photon blockade with simultaneous suppression of unwanted one- and three-photon components at a comparable two-photon population. In another parameter regime, strongly correlated fluorescence photon pairs can also be generated from the two atoms by selecting the double-atomic-excitation component in the same two-excitation manifold. This approach provides a route toward high-quality and versatile two-photon sources, with potential applications in few-photon quantum optics and quantum information processing.
Abstract Photon blockade in weakly nonlinear resonators is often limited by a trade-off among antibunching, resonant excitation, and tunability. We consider a driven two-mode bosonic system coupled by photon-pair exchange. The exchange interaction vanishes in the one-photon manifold but couples the target and auxiliary two-photon states. Destructive interference can therefore suppress the leading target two-photon amplitude without detuning the target mode. In the weak-drive limit, we derive the required drive-amplitude ratio and relative phase, together with the leading correction due to an auxiliary-mode Kerr shift. Steady-state master-equation calculations confirm the analytical condition and quantify the effects of finite drive, loss asymmetry, pair mismatch, residual nonlinearities, single-photon hopping, dephasing, phase fluctuations, and thermal occupation. Under the stated matched linewidth, coherent-drive, and nonlinear-resource convention, the resonant pair-exchange scheme yields a target single-photon population approximately 9.5 times that of an optimized canonical Kerr-UPB benchmark at g a ( 2 ) ( 0 ) ⩽ 10 − 2 . A normalized post-fabrication recovery test further shows that external-drive recalibration restores the interference minimum across the sampled uncertainty window. These results support photon-pair exchange as a controllable route to continuous-wave resonant antibunched emission.
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.
We propose a scheme to realize tunable and strong nonreciprocal photon blockade (PB) in an asymmetric Fabry-Pérot cavity. The setup consists of a single-mode optical cavity trapping a two-level atom, with the cavity coherently driven by a laser and the atom pumped by an auxiliary control field of the same frequency. By engineering quantum interference between multiple excitation pathways by adjusting the amplitude and relative phase of the control laser, we identify two distinct optimal control conditions that enable directional suppression of two-photon states. Under optimal control conditions, strong nonreciprocal PB is achieved, with a nonreciprocal ratio exceeding 30 dB over a broad operational bandwidth. The proposed protocol requires only standard coherent laser sources and is compatible with current cavity QED experimental setups, offering a practical and scalable platform for nonreciprocal quantum photonics.
Abstract Following the coupling-spanning resonance-and-interference construction introduced by Zhou et al , we use ‘universal’ only in this inherited finite-coupling sense. Here we show that the complex amplitude of a parametric drive provides direct control of this interference in a coherently driven Jaynes–Cummings (JC) system. In the weak-driving limit, imposing C 2 g = 0 on the lossless one-excitation reference line gives an analytical pump condition Λ 1 . Over 0.05 ⩽ g / κ ⩽ 8 , the full steady states satisfy the adopted 1PB photon-statistics characterization. The required pump remains finite as g → 0 , but the exactly decoupled cavity is Gaussian and serves only as a Gaussian-interference antibunching reference, not as JC photon blockade. At the two-excitation reference resonance, imposing C 3 g = 0 while retaining C 2 g ≠ 0 gives a second analytical pump condition. Full steady-state master-equation calculations, including photon-number probabilities, identify finite parameter regions satisfying both the correlation and equal-mean Poisson criteria for two-photon blockade (2PB). A matched-Gaussian diagnostic shows that the weak-coupling end remains nearly Gaussian, whereas at stronger coupling the matched Gaussian state no longer reproduces the full g ( 2 ) ( 0 ) . For fixed system and coherent-drive parameters, the two pump values Λ 1 and Λ 2 select steady states with 1PB and 2PB statistics. The fixed-parameter 2PB endpoint has a small two-photon probability and is not a brightness-optimized photon-pair source; at a vacuum-input extraction port, normalized output correlations equal the intracavity values.