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Chinese Physics B

In-phase collective unconventional photon blockade and its stability in an asymmetrical cavity containing N bosonic atoms

Ying She Luo, Xinqin Zhang, Yi Xiao, Jingping Xu, Haozhen Li, Yaping Yang, Xiuwen Xia

Published Oct 30, 2024• 2 citations
Publisher

Abstract

Abstract We present work on a cavity-driven QED system combining an asymmetrical Fabry–Perot cavity and N two-level atoms (TLAs) and show the convenience of simplifying from distinguishable atoms to undistinguishable bosons when the atoms are prepared in the same initial state. Such simplification is valid even when the atoms are not prepared in the in-phase condition, since any partial in-phase initial state will evolve into the ground state through a relaxation process. Thus, we get a reduced group of differential equations by introducing the Dicke states, and the under-zero Lyapunov exponents verify its stability. We also work out the collective unconventional photon blockade (UCPB) and get two kinds of giant nonreciprocal UCPBs (NUCPBs) in the weak-driving approximation. Results show that we can employ N noninteracting bosonic atoms to generate a collective UCPB instead of a monoatomic UCPB as the UCPB conditions do not vary with the number of atoms. Furthermore, the forward giant NUCPB only occurring for N larger than a certain number as well as the backward giant NUCPB are controllable by the cavity asymmetry and by the number of atoms. Our findings suggest a prospective approach to the generation of quantum nonreciprocity by N identical atoms.

DOI
10.1088/1674-1056/ad8cbf

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Abstract We present work on a cavity-driven QED system combining an asymmetrical Fabry–Perot cavity and N two-level atoms (TLAs) and show the convenience of simplifying from distinguishable atoms to undistinguishable bosons when the atoms are prepared in the same initial state. Such simplification is valid even when the atoms are not prepared in the in-phase condition, since any partial in-phase initial state will evolve into the ground state through a relaxation process. Thus, we get a reduced group of differential equations by introducing the Dicke states, and the under-zero Lyapunov exponents verify its stability. We also work out the collective unconventional photon blockade (UCPB) and get two kinds of giant nonreciprocal UCPBs (NUCPBs) in the weak-driving approximation. Results show that we can employ N noninteracting bosonic atoms to generate a collective UCPB instead of a monoatomic UCPB as the UCPB conditions do not vary with the number of atoms. Furthermore, the forward giant NUCPB only occurring for N larger than a certain number as well as the backward giant NUCPB are controllable by the cavity asymmetry and by the number of atoms. Our findings suggest a prospective approach to the generation of quantum nonreciprocity by N identical 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 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.
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 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.
In this paper, we show that the photon blockade (PB) can be observed in a nonreciprocal way with a driven spinning atom-cavity coupled filled with [Formula: see text] nonlinear medium. We analytically derive the optimal conditions for strong photon antibunching, which are in good agreement with those obtained by numerical simulations. Under the weak driving condition, we discuss the physical origins of the nonreciprocal unconventional photon blockade (UPB), which originates from the destructive quantum interference between different paths from the ground state to two-photon states by driving the device from the left side. While the quantum interference paths are broken when the device is driven from the right side, which leads to the occurrence of the photon bunching. Moreover in the opposite direction of driving the device, we also observe another nonreciprocal UPB effect, which can occur by generating bunching and antibunching effects via driving the device from the left and right sides under the derived optimal conditions, respectively. Finally, we cannot observe the nonreciprocal UPB phenomenon with the large cavity decay compared to the atomic spontaneous emission rate (or the bad cavity limit), and give the physical reason behind it. Possible experimental implementation for this scheme is presented.
In this paper, we show that nonreciprocal unconventional photon blockade can be observed in a spinning cavity immersed in a degenerate optical parametric amplifier (OPA) driven by the laser driving with weak Kerr nonlinearities through the Fizeau drag. We analytically derive the optimal conditions for strong antibunching, which are in good agreement with those obtained by numerical simulations. Under the weak driving condition, we discuss the physical origins of the nonreciprocal unconventional photon blockade, which originates from the destructive interference between different paths from the ground state to two-photon states by driving the device from the left side. While the quantum interference paths are broken when the device is driven from the right side, which leads to the occurring of the photon bunching. Moreover, we extend the above results to the general non-Markovian regimes, in which the cavity couples with a thermal reservoir consisting of collection of infinite oscillators (bosonic photonic modes). We show nonreciprocal unconventional photon blockade exhibits a transition from the non-Markovian to Markovian regimes by controlling environmental spectral width regardless of the weakness of OPA gain and driving field.