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arXiv:2402.09000 · Physical Review Letters

Chiral Interaction Induced Near-Perfect Photon Blockade

Zhi-Guang Lu, Ying Nian Wu, Xin‐You Lü

Published Jan 6, 2025• 33 citations
arXivHTMLPDF

Abstract

Based on the scattering matrix method, we theoretically demonstrate that the chiral interaction can induce the almost perfect photon blockade (PB) in the waveguide-cavity quantum electrodynamics system. The mechanism relies on the multiphoton path's interference within the waveguide, which is clearly shown by the analytic parameter regime for g^{(2)}(0)≈0. When N cavities are introduced into the system, there are N optimal parameter points accordingly for the almost perfect PB, where the required lowest chirality decreases exponentially with increasing N, and these optimal points are robust against disorder in the system's frequencies. Under resonant driving and fixed chirality conditions, the output light depends solely on the parity of N (N≥2), with a coherent state emerging for even numbers of cavities and a single-photon state for odd numbers. Our Letter offers an alternative route for achieving almost perfect PB effects with high single-photon transmission by employing the chirality of system, with potential application in the on-chip single-photon source with integrability.

DOI
10.1103/physrevlett.134.013602

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Based on the scattering matrix method, we theoretically demonstrate that the chiral interaction can induce the almost perfect photon blockade (PB) in the waveguide-cavity quantum electrodynamics system. The mechanism relies on the multiphoton path's interference within the waveguide, which is clearly shown by the analytic parameter regime for g^{(2)}(0)≈0. When N cavities are introduced into the system, there are N optimal parameter points accordingly for the almost perfect PB, where the required lowest chirality decreases exponentially with increasing N, and these optimal points are robust against disorder in the system's frequencies. Under resonant driving and fixed chirality conditions, the output light depends solely on the parity of N (N≥2), with a coherent state emerging for even numbers of cavities and a single-photon state for odd numbers. Our Letter offers an alternative route for achieving almost perfect PB effects with high single-photon transmission by employing the chirality of system, with potential application in the on-chip single-photon source with integrability.
We investigate the generation of nonreciprocal single photons in the chiral waveguide-cavity-emitter system. Due to the chirality of light-emitter interactions, photons in the left direction couple to a cavity which induces only linear optical effects, while photons in the right direction couple to a cavity-emitter system which can generate optical nonlinearity. In the regime of single-photon transmission, photons in the left direction are absorbed by the cavity at the resonance frequency, while photons in the right direction are transmitted due to the Rabi splitting. In the regime of two-photon transmission, optical linearity in the left direction cannot produce photon-photon interactions and does not change the statistics of photons. However, the effective repulsive interaction between photons can be produced by the optical nonlinearity in the right direction, suppressing two-photon transmission (photon blockade). Physically, the photon-photon bound state, which emerges due to the strong-photon-photon correlation mediated by the cavity-emitter system, plays a key role in generation of photon blockade at the resonance frequency. As a result, nonreciprocal single photons can be realized in the combination of single-photon transmission and photon blockade at the resonance frequency. Additionally, photon-photon interactions are sensitive to the width of the wave packet since photons should coincide at the interaction site.
We introduce a method to achieve nonreciprocal photon blockade in an optical resonator that is chirally coupled to a two-level atom. This approach enables single-excitation and two-excitation resonant conditions to be simultaneously satisfied. The atom-uncoupled optical mode can be blocked with eliminating its two-photon excitation by judiciously selecting parameters, e.g., the optical coupling strength. The chiral interaction between the resonator mode and the atom leads to different optimal parameter conditions for generating photon blockade in the two opposite drivings. This offers a natural way to realize nonreciprocal photon blockade. The nonreciprocity achieved by the chiral cavity-atom interaction diminishes the experimental difficulty by eliminating the need to rotate the resonator. The blockade mode achieves very high purity of single-photon excitation, as characterized by a second-order correlation function of ${g}^{(2)}(0)\ensuremath{\sim}{10}^{\ensuremath{-}4}$. In particular, in the nonreciprocal regime, the mean number of photons is significantly higher where photon blockade occurs compared to the general Jaynes-Cummings case. Our findings are particularly relevant for the development of quantum nonreciprocal devices and their applications in quantum information processing, including chiral networks.
The photon blockade (PB) effect is a hallmark non-classical phenomenon in quantum optics and finds important applications for building quantum sources, while the control of PB by the non-Hermitian exceptional points remains largely unexplored. In this work, we theoretically investigate universal photon blockade in a microcavity harboring chiral exceptional points (CEPs) for building multiplexing quantum sources with nonreciprocal photon statistics. The results reveal that the presence of the CEPs leads to a stark contrast in the photon statistics of two whispering-gallery modes with opposite propagating directions. That is, one mode exhibits a strong PB effect while the other displays either sub-Poissonian or super-Poissonian distribution. Our findings thus may pave the way for advanced applications of photon blockade, and provide a theoretical foundation for the selective generation of single-photon and two-photon emission
Photon blockade (PB) is one of the effective methods to generate single-photon sources. In general, both the PB effect with the significant sub-Poissonian statistics and a large mean photon number are desired to guarantee the brightness and the purity of single-photon sources. Here, we propose to obtain the PB effect at the cavity dark-state polariton (DSP) using a cavity Λ-type electromagnetically induced transparency (EIT) system with and without the two-photon dissipation (TPD). In the Raman resonance case, the PB effect at the DSP could by realized by using the TPD process in the weak or intermediate coupling regime, which accompanies with near unity transmission, i.e., very high photon occupation. In the slightly detuned Raman resonance case, the excited state is induced into the components of the DSP, and the atomic dissipation path is added into the two-photon excitation paths. Thus, the PB effect at the DSP can be obtained due to the quantum destructive interference (QDI) in the strong coupling regime, which can be further enhanced using the TPD process. Due to the slight detuning, the PB effect still remains high photon occupation and has highly tunability. This work provides an alternative way to manipulate the photon statistics by the PB effect and has potential applications in generating single-photon sources with high brightness and purity.
Strongly correlated photons play a crucial role in modern quantum technologies. Here, we investigate the probability of generating strongly correlated photons in a chain of N qubits coupled to a one-dimensional waveguide. We found that disorder in the transition frequencies can induce photon antibunching and especially nearly perfect photon blockade events in the transmission and reflection outputs. As a comparison, in ordered chains, strongly correlated photons cannot be generated in the transmission output, and only weakly antibunched photons are found in the reflection output. The occurrence of nearly perfect photon blockade events stems from the disorder-induced nearly completely destructive interference of photon scattering paths. Our Letter highlights the impact of disorder on photon correlation generation and suggests that disorder can enhance the potential for achieving strongly correlated photons.
We propose an scheme for directional single-photon source based on a chiral cavity-magnon system. In this system, the magnon mode in a single-crystal yttrium iron garnet (YIG) sphere is coupled to only one of two rotating microwave modes in the torus-shaped microwave cavity. When two-photon drives are applied to both ports of the waveguide, the chiral cavity-magnon coupling leads to an unconventional photon blockade in one propagation direction, resulting in directional single-photon emission. The emission direction of the single-photon source can be controlled by reversing the biased magnetic field. Furthermore, we further examine the effects of imperfect chiral cavity-magnon coupling and the coupling between the two cavity modes on the photon blockade behavior. The results show that the system retains robustness in the presence of these nonideal factors, and the unidirectional photon blockade effect remains clearly preserved.