Title: Ultra-coherent nanomechanical resonators via soft clamping and dissipation dilution Show Chinese title

Title: 通过软钳位和损耗稀释实现超相干纳米机械谐振器

Abstract: The small mass and high coherence of nanomechanical resonators render them the ultimate force probe, with applications ranging from biosensing and magnetic resonance force microscopy, to quantum optomechanics. A notorious challenge in these experiments is thermomechanical noise related to dissipation through internal or external loss channels. Here, we introduce a novel approach to defining nanomechanical modes, which simultaneously provides strong spatial confinement, full isolation from the substrate, and dilution of the resonator material's intrinsic dissipation by five orders of magnitude. It is based on a phononic bandgap structure that localises the mode, without imposing the boundary conditions of a rigid clamp. The reduced curvature in the highly tensioned silicon nitride resonator enables mechanical $Q>10^{8}$ at $ 1 \,\mathrm{MHz}$, yielding the highest mechanical $Qf$-products ($>10^{14}\,\mathrm{Hz}$) yet reported at room temperature. The corresponding coherence times approach those of optically trapped dielectric particles. Extrapolation to $4{.}2$ Kelvin predicts $\sim$quanta/ms heating rates, similar to trapped ions. Show Chinese abstract

Abstract: 纳米机械谐振子的小质量和高相干性使其成为终极的力探针，在生物传感、磁共振力显微镜以及量子光机械学等领域有着广泛的应用。然而，在这些实验中一个众所周知的挑战是与内部或外部损耗通道相关的热机械噪声。 在这里，我们介绍了一种定义纳米机械模式的新方法，该方法同时提供了强大的空间限制、完全的基底隔离，并将谐振器材料的本征耗散降低了五个数量级。它基于一种声子带隙结构，这种结构可以局部化模式，而无需施加刚性夹具的边界条件。高度张紧的氮化硅谐振器中的曲率减小使得在室温下实现了机械$Q>10^{8}$模式频率达到$ 1 \,\mathrm{MHz}$，获得了迄今为止报道的最高的机械$Qf$-乘积 ($>10^{14}\,\mathrm{Hz}$)。对应的相干时间接近光学捕获的介电粒子的相干时间。外推到$4{.}2$开尔文预测加热速率为$\sim$量子/毫秒，类似于囚禁离子。