We report quantum ground state cooling of a levitated nanoparticle in a room temperature environment. Using coherent scattering into an optical cavity we cool the center of mass motion of a $143$ nm diameter silica particle by more than $7$ orders of magnitude to $n_x=0.43\pm0.03$ phonons along the cavity axis, corresponding to a temperature of $12~\mu$K. We infer a heating rate of $\Gamma_x/2\pi = 21\pm 3$ kHz, which results in a coherence time of $7.6~\mu$s -- or $15$ coherent oscillations -- while the particle is optically trapped at a pressure of $10^{-6}$ mbar. The inferred optomechanical coupling rate of $g_x/2\pi = 71$ kHz places the system well into the regime of strong cooperativity ($C \approx 5$). We expect that a combination of ultra-high vacuum with free-fall dynamics will allow to further expand the spatio-temporal coherence of such nanoparticles by several orders of magnitude, thereby opening up new opportunities for macrosopic quantum experiments.

中文翻译：

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悬浮的纳米粒子冷却到运动量子基态

我们报告了悬浮纳米粒子在室温环境中的量子基态冷却。使用进入光学腔的相干散射，我们将直径为 143 纳米的二氧化硅粒子的质心运动冷却了超过 7 美元的数量级，使声子沿腔轴冷却，对应于温度$12~\mu$K。我们推断出加热速率为 $\Gamma_x/2\pi = 21\pm 3$ kHz，这导致相干时间为 $7.6~\mu$s - 或 $15$ 相干振荡 - 而粒子被光学捕获在10 美元 ^{-6} 美元毫巴的压力。推断出的光机械耦合率 $g_x/2\pi = 71$ kHz 将系统置于强协同性（$C \约 5$）的状态。