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Physical Review Research

Photon blockade and single-photon generation with multiple quantum emitters

Mingyuan Chen, Jiang-Shan Tang, Lei Tang, Haodong Wu, Keyu Xia

Published Jul 29, 2022• 33 citations
Publisher

Abstract

Generation and manipulation of single photons are at the heart of photon-based quantum information processing. An ensemble of quantum emitters (QEs) as a versatile light-matter interface are very promising for quantum technology such as quantum storage and repeater. However, it is commonly believed that many QEs are unable to create photon blockade and generate single photons with high purity due to the multiexcitation effect. Here, we show efficient photon blockade and single-photon generation with a few to ten QEs by suppressing multiexcitation with a detuned auxiliary cavity. Because the auxiliary cavity induces a strong dipole-dipole interaction among the QEs, these QEs can be treated as a two-level superatom. By coupling this superatom to another collecting cavity, efficient photon blockade with a high transmission is obtained. With the same setup, single-photon emission can also be achieved with yield and purity larger than $90%$ simultaneously even in the bad-cavity limit. Our method may open up a simple route to generate and manipulate single photons on demand.

DOI
10.1103/physrevresearch.4.033083

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Generation and manipulation of single photons are at the heart of photon-based quantum information processing. An ensemble of quantum emitters (QEs) as a versatile light-matter interface are very promising for quantum technology such as quantum storage and repeater. However, it is commonly believed that many QEs are unable to create photon blockade and generate single photons with high purity due to the multiexcitation effect. Here, we show efficient photon blockade and single-photon generation with a few to ten QEs by suppressing multiexcitation with a detuned auxiliary cavity. Because the auxiliary cavity induces a strong dipole-dipole interaction among the QEs, these QEs can be treated as a two-level superatom. By coupling this superatom to another collecting cavity, efficient photon blockade with a high transmission is obtained. With the same setup, single-photon emission can also be achieved with yield and purity larger than 9090%90 simultaneously even in the bad-cavity limit. Our method may open up a simple route to generate and manipulate single photons on demand.
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.
The on-chip generation of nonclassical states of light is a key requirement for future optical quantum hardware. In solid-state cavity quantum electrodynamics, such nonclassical light can be generated from self-assembled quantum dots strongly coupled to photonic crystal cavities. Their anharmonic strong light-matter interaction results in large optical nonlinearities at the single photon level, where the admission of a single photon into the cavity may enhance (photon tunneling) or diminish (photon blockade) the probability for a second photon to enter the cavity. Here, we demonstrate that detuning the cavity and quantum-dot resonances enables the generation of high-purity nonclassical light from strongly coupled systems. For specific detunings we show that not only the purity but also the efficiency of single-photon generation increases significantly, making high-quality single-photon generation by photon blockade possible with current state-of-the-art samples.
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)g^{(2)}(0)g(2)(0), and essentially preserves the single-photon population. As the emitter number NNN increases, the optimal point remains at Δc=0Δ_c=0Δc​=0, while the minimum correlation follows gmin⁡(2)(0)∝N−2g_{\min}^{(2)}(0)\propto N^{-2}gmin(2)​(0)∝N−2. By contrast, unconventional photon blockade shifts away from resonance as NNN increases, limiting its purity improvement and brightness. In the weak-drive regime, universal blockade obeys g(2)(0)∝εa2g^{(2)}(0)\propto\varepsilon_a^2g(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 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.
Photon blockade is vital for single-photon generation, but current schemes with conventional and unconventional photon blockade face critical limitations like the purity-brightness trade-off, hindering the generation of high-performance single-photons. To overcome these limitations, we introduce a fundamentally new photon blockade mechanism by utilizing three-body interactions between a single photonic mode and two qubits. This kind of interaction intrinsically cuts off the excitation path to the two-photon state, resulting in a perfect photon blockade effect. The mechanism operates across a broad parameter range, free from the constraints of strong coupling or weak driving. Remarkably, it breaks the purity-brightness trade-off, enabling the simultaneous achievement of extreme purity and high brightness, both significantly outperforming previous mechanisms. Furthermore, this approach demonstrates robustness against thermal noise and avoids unwanted oscillations in the time-delayed correlation function. This work provides a path for generating high-purity, high-brightness, and robust single-photon sources, a key resource for quantum technologies.
Abstract Quantum optics based on highly excited atoms, also known as Rydberg atoms, has cemented itself as a powerful platform for the manipulation of light at the few-photon level. The Rydberg blockade, resulting from the strong interaction between individual Rydberg atoms, can turn a large ensemble of atoms into a system which collectively resembles a single two-level emitter, a so-called Rydberg superatom. The coupling of this artificial emitter to a driving photonic mode is collectively enhanced by Rydberg interactions, enabling strong coherent coupling at the few-photon level in free-space. The exquisite level of control achievable through this has already demonstrated its utility in applications of quantum computing and information processing. Here, we review the derivation of the collective coupling between a Rydberg superatom and a single light mode and discuss the similarity of this free-space setup to waveguide quantum electrodynamics systems of quantum emitters coupled to photonic waveguides. We also briefly review applications of Rydberg superatoms to quantum optics such as single-photon generation and single-photon subtraction.