利用斯塔克非线性耦合实现无级联通道的增强型双光子阻塞
Enhanced two-photon blockade without cascade channel by Stark nonlinear coupling
AI总结：
本研究提出用斯塔克非线性耦合增强无级联通道的非常规双光子阻塞，将其窗口拓宽至整个强耦合区、阻塞程度加深两个数量级，为双光子阻塞操控提供实用方案。
AI中文摘要：
双光子阻塞（TPB）与传统单光子阻塞类似，可在光-物质耦合系统的输入输出测量中实现对光子的单量子水平控制。除了具有开放级联衰减通道的传统双光子阻塞（C-TPB）外，具有闭合级联衰减通道的非常规双光子阻塞（U-TPB）可能为双光子阻塞的操控开辟新途径。然而，目前在线性耦合中发现的U-TPB仅局限于狭窄的耦合窗口，且阻塞强度较弱，这会阻碍其应用。本工作中，我们提出利用斯塔克非线性耦合来增强U-TPB。将斯塔克非线性耦合引入线性耦合，可对形成双光子阻塞起关键作用的级联能级和谐振子非谐性进行调控。通过研究光子关联函数并提取耗散下的相图，我们证明该方案不仅能将U-TPB的窗口大幅拓宽至覆盖整个强耦合区域，还能将U-TPB的阻塞程度加深两个数量级。我们还对级联衰减率、态布居数和非谐性进行了考察，以识别和追踪U-TPB与C-TPB。在相图的整体分析中，我们还揭示了超强耦合下存在的宽范围U-TPB，其可交叉过渡到C-TPB。由于斯塔克非线性耦合是可实现且可定制的，我们的方案可能为双光子阻塞的操控开辟一条实用途径。
英文摘要：
Two-photon blockade (TPB) besides the conventional one-photon blockade can control the photon at the level of individual quanta in the input-output measurements of light-matter coupling systems. Apart from conventional TPB (C-TPB) with opened cascade decay channel, unconventional TPB (U-TPB) with closed cascade decay channel may open novel avenues for manipulation of TPB. However, currently found U-TPB in linear coupling is limited in a narrow coupling window and the blockade strength is weak, which would hinder its applications. In the present work we propose to enhance the U-TPB by the Stark nonlinear coupling. Indeed, the introduction of the Stark nonlinear coupling to the linear coupling enables tuning of both cascade energy level and the anharmonicity which play key roles in the formation of TPBs. By investigating photon correlation functions and extracting phase diagrams in dissipation, we demonstrate that our scheme not only dramatically broadens the window of U-TPB to cover the entire strong-coupling regime but also deepens the blockading degree of the U-TPB by two orders. The cascade decay rates, state populations and the anharmonicity, are examined to identify and track the U-TPB and C-TPB. In the overview of phase diagrams we also reveal a broad U-TPB in ultrastrong couplings, with a crossover to the C-TPB. Since the Stark nonlinear coupling is realizable and tailorable, our proposal may pave a practical way for manipulation of the TPB.
