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Optics Express

Improvement of nonreciprocal unconventional photon blockade by two asymmetrical arranged atoms embedded in a cavity

Xiuwen Xia, Xinqin Zhang, Jingping Xu, Haozhen Li, Zeyun Fu, Yaping Yang

Published Feb 15, 2022• 16 citations
Publisher

Abstract

We improve the nonreciprocal unconventional photon blockade (UCPB) in an asymmetrical single-mode cavity with two asymmetrical arranged two-level atoms (TLAs) where cavity and atom spatial symmetry breakings are involved in. In order to get direction-dependent UCPB in asymmetrical system, we deduce two restrictions of frequency and intensity through the steady solution of the cavity QED system analytically. The former restriction is exactly the same as that of a single-atom case, and the latter restriction combined with both spatial asymmetries. Controllable UCPB in this model shows an improving nonreciprocal UCPB with wider operating regime which is promoted by two asymmetrical arranged atoms. The most innovation of this work is that the contributions of two spatial symmetry breakings are figured out clearly and they play different roles in nonreciprocal UCPB. The cavity spatial symmetry breaking and weak nonlinearity are essential to quantum nonreciprocity, while the atoms spatial symmetry is not and it only can promote such nonreciprocal UCPB. Our findings show a prospective access to manipulate quantum nonreciprocity by a couple of atoms.

DOI
10.1364/oe.450585

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We improve the nonreciprocal unconventional photon blockade (UCPB) in an asymmetrical single-mode cavity with two asymmetrical arranged two-level atoms (TLAs) where cavity and atom spatial symmetry breakings are involved in. In order to get direction-dependent UCPB in asymmetrical system, we deduce two restrictions of frequency and intensity through the steady solution of the cavity QED system analytically. The former restriction is exactly the same as that of a single-atom case, and the latter restriction combined with both spatial asymmetries. Controllable UCPB in this model shows an improving nonreciprocal UCPB with wider operating regime which is promoted by two asymmetrical arranged atoms. The most innovation of this work is that the contributions of two spatial symmetry breakings are figured out clearly and they play different roles in nonreciprocal UCPB. The cavity spatial symmetry breaking and weak nonlinearity are essential to quantum nonreciprocity, while the atoms spatial symmetry is not and it only can promote such nonreciprocal UCPB. Our findings show a prospective access to manipulate quantum nonreciprocity by a couple of atoms.
We present a work of manipulating collective unconventional photon blockade (UCPB) and nonreciprocal UCPB (NUCPB) in a cavity-driven system composed of an asymmetrical single-mode cavity and two interacting identical two-level atoms (TLAs). When the atoms do not interact directly, the frequency and intensity restrictions of collective UCPB can be specified, and a giant NUCPB exists due to the splitting of optimal atom–cavity coupling strength in proper parameter regime. However, if a weak atom–atom interaction which provides a new and feeble quantum interference pathway to UCPB is taken into account, two restrictions of UCPB are combined complexly, which are rigorous to be matched simultaneously. Due to the push-and-pull effect induced by weak dipole–dipole interaction, the UCPB regime is compressed more or less. NUCPB is improved as a higher contrast is present when the two complex UCPB restrictions are matched, while it is suppressed when the restrictions are mismatched. In general, whether NUCPB is suppressed or promoted depends on its working parameters. Our findings show a prospective access to produce giant quantum nonreciprocity by a couple of weakly interacting atoms.
Inspired by the advantage of unconventional photon blockade (UCPB), we propose a simple cavity-driven quantum electrodynamics model composed of a single two-level atom embedded in an asymmetrical Fabry-Perot cavity. We derive the necessary matching conditions of frequency and intensity required for unconventional photon blockade. In the asymmetric cavity, the optimal atom-cavity coupling strength to get UCPB is related to the driving direction, which causes the equal-time second-order correlation function g(2)(0){g}^{(2)}(0)g(2)(0) of the cavity field depending on the driving direction, too. Due to the direction dependent effect, the output photons can be bunched in one direction incident while they are antibunched in the opposite direction incident, which is the so-called nonreciprocal UCPB (NUCPB). A giant NUCPB can be obtained under the appropriate parameter regime, where the output photons are fully antibunching in the opposite driving case. Our findings show a prospective path to producing giant quantum nonreciprocity.
We propose a scheme to manipulate strong and nonreciprocal photon blockades in asymmetrical Fabry-Perot cavity with a Λ-type three-level atom. Utilizing the mechanisms of both conventional and unconventional blockade, the strong photon blockade is achieved by the anharmonic eigenenergy spectrum brought by Λ-type atom and the destructive quantum interference effect induced by a microwave field. By optimizing the system parameters, the manipulation of strong photon blockade over a wide range of cavity detuning can be realized. Using spatial symmetry breaking introduced by the asymmetry of cavity, the direction-dependent nonreciprocal photon blockade can be achieved, and the nonreciprocity can reach the maximum at optimal cavity detuning. In particular, manipulating the occurring position of nonreciprocal photon blockade can be implemented by simply adjusting the cavity detuning. Our scheme provides feasible access for generating high-quality nonreciprocal single-photon sources.
We propose a scheme to generate and manipulate nonreciprocal photon blockade effect in an asymmetrical Fabry-P\'erot cavity, which consists of a single two-level atom and a second-order nonlinear medium. By utilizing the intrinsic spatial asymmetry of cavity and applying a parametric amplification pumping laser to the nonlinear medium, we can realize direction-dependent single-photon and two-photon blockade effects. For nonreciprocal single-photon blockade, our proposal is robust across a wide range of parameters, such as the cavity or atomic detuning, coupling strength, and atomic decay. Within similar parameter ranges, nonreciprocal two-photon blockade can be achieved and modulated by finely adjusting the parametric amplification pumping. Our project offers a feasible access to generating high-quality and tunable nonreciprocal single- or two-photon sources and paves a new avenue for investigating the nonreciprocity of photon quantum statistical properties.
We present a work of promoted optical nonreciprocity (ONR) in an asymmetrical cavity containing two asymmetrically arranged two-level atoms with a weak atom-atom interaction. The input-output relation is worked out by using a perturbative approach. Results show that the bistable-monostable-bistable phase transition would exist when the second atom is present, where the optical bistability and nonreciprocity change considerably. Contributions of two types of spatial asymmetries suggest that the ONR originates from the cooperation of the cavity spatial symmetry breaking and the optical nonlinearity, regardless of the atomic spatial symmetry breaking. In addition to the experimentally proved bistable ONR, a type of monostable ONR is proposed, which operates in the monostable phase. Both the ONR optimal regime and the block rate are boosted by adding the other atom in the cavity. Our findings suggest a prospective approach to the generation of a giant ONR by two atoms with unequal atom-cavity coupling strengths.
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.