[论文解读] Multimode amplitude squeezing through cascaded nonlinear optical processes

Sahil Pontula, Yannick Salamin+2 more|arXiv (Cornell University)|May 8, 2024

Advanced Fiber Laser Technologies被引用 4

一句话总结

本文提出一种具有工程化Q因子的级联非线性光学腔，以在离散频率模式中实现超过10 dB的多模振幅压缩，低于散粒噪声极限。通过利用共用的闲频浴模式并构建支持布洛赫振荡的合成频率腔，该系统通过增强非线性耦合相对于耗散的效应，实现了在多个模式上的可调谐、高亮度压缩。

ABSTRACT

Multimode squeezed light is enticing for several applications, from squeezed frequency combs for spectroscopy to signal multiplexing in optical computing. To generate squeezing in multiple frequency modes, optical parametric oscillators have been vital in realizing multimode squeezed vacuum states through second-order nonlinear processes. However, most work has focused on generating multimode squeezed vacua and squeezing in mode superpositions (supermodes). Bright squeezing in multiple discrete frequency modes, if realized, could unlock novel applications in quantum-enhanced spectroscopy and optical quantum computing. Here, we show how $Q$ factor engineering of a multimode nonlinear cavity with cascaded three wave mixing processes creates strong, spectrally tunable single mode output amplitude noise squeezing over 10 dB below the shot noise limit. In addition, we demonstrate squeezing for multiple discrete frequency modes above threshold. This bright squeezing arises from enhancement of the (noiseless) nonlinear rate relative to decay rates in the system due to the cascaded generation of photons in a single idler "bath" mode. A natural consequence of the strong nonlinear coupling in our system is the creation of an effective cavity in the synthetic frequency dimension that sustains Bloch oscillations in the modal energy distribution. Bloch mode engineering could provide an opportunity to better control nonlinear energy flow in the synthetic frequency dimension, with exciting applications in quantum random walks and topological photonics. Lastly, we show evidence of long-range correlations in amplitude noise between discrete frequency modes, pointing towards the potential of long-range entanglement in a synthetic frequency dimension.

研究动机与目标

• 通过级联参量过程在多个离散频率模式中实现高亮度振幅压缩。
• 通过工程化非线性耦合与耗散，突破单过程振幅压缩的3 dB理论极限。
• 探讨合成频率维度在调控非线性能量流与量子噪声中的作用。
• 研究长程振幅噪声相关性作为频率空间中潜在长程纠缠的特征。
• 为量子增强光谱学和光学计算等应用，实现可调谐、宽带且光谱选择性的压缩。

提出的方法

• 利用具有级联三波混频过程的多模非线性腔，通过共享的闲频'浴'模式耦合多个信号模式。
• 在频率域中工程化Q因子分布，以增强非线性耦合相对于衰减率的比值，从而形成合成频率腔。
• 利用合成频率维度中的反向传播布洛赫模式，生成模态能量分布中的驻波图案。
• 采用基于光子晶体的可调谐频率滤波器，选择性控制单个频率模式的出耦合（Q因子）。
• 使用包含强多模耦合引起的弛豫振荡的耦合非线性微分方程，建模平均场动力学与量子噪声。
• 通过线性化区域中的完整量子朗之万方程与海森堡-朗之万形式，分析噪声相关性与压缩谱。

Figure 1: Squeezing in a multimode cavity with THz-mediated cascaded three wave mixing. (a) Cascading infrared (IR) orders are resonant in a multimode cavity and undergo three wave mixing (TWM) mediated by a terahertz (THz) mode, creating a frequency comb (red) with modes separated by the THz freque

实验结果

研究问题

• RQ1 在多模腔中，级联非线性过程是否能在多个离散频率模式中实现超过3 dB极限的振幅压缩？
• RQ2 在合成频率维度中Q因子的工程化如何影响振幅压缩的强度与光谱分布？
• RQ3 布洛赫振荡及反向传播模式之间的干涉在塑造稳态能量分布与噪声特性方面起什么作用？
• RQ4 频率空间中的长程振幅噪声相关性是否可作为合成维度中长程量子纠缠存在的指示？
• RQ5 该平台在多大程度上可用于生成可调谐、高亮度的压缩频率梳以用于量子应用？

主要发现

• 通过Q因子工程与级联非线性耦合，系统实现了单模振幅压缩超过10 dB，低于散粒噪声极限。
• 在阈值以上，多个离散频率模式中实现了同时的多模振幅压缩，带宽超过100 MHz。
• 合成频率腔支持布洛赫振荡与反向传播模式，导致模态能量分布中出现驻波图案。
• 在离散频率模式之间观察到强烈的长程振幅噪声相关性，表明在合成频率维度中可能存在长程纠缠。
• 通过调节单个模式的出耦合Q因子，可实现对哪些模式被压缩的可调谐控制。
• 理论分析证实，非线性耦合相对于耗散的增强是实现强压缩的关键机制，与无噪声速率增强一致。

Figure 2: Intracavity dynamics and noise due to strong cascaded nonlinear interactions. (a) $Q$ factor shaping (through the use of frequency-dependent couplers) permits the creation of frequency combs containing only redshifted modes relative to the pump mode $a_{0}$ . The temporal dynamics feature