Militaru Andrei, Rossi Massimiliano, Tebbenjohanns Felix, Romero-Isart Oriol, Frimmer Martin, Novotny Lukas
Photonics Laboratory, ETH Zürich, CH-8093 Zürich, Switzerland.
Institute for Quantum Optics and Quantum Information of the Austrian Academy of Sciences, A-6020 Innsbruck, Austria.
Phys Rev Lett. 2022 Jul 29;129(5):053602. doi: 10.1103/PhysRevLett.129.053602.
A mechanically compliant element can be set into motion by the interaction with light. In turn, this light-driven motion can give rise to ponderomotive correlations in the electromagnetic field. In optomechanical systems, cavities are often employed to enhance these correlations up to the point where they generate quantum squeezing of light. In free-space scenarios, where no cavity is used, observation of squeezing remains possible but challenging due to the weakness of the interaction, and has not been reported so far. Here, we measure the ponderomotively squeezed state of light scattered by a nanoparticle levitated in a free-space optical tweezer. We observe a reduction of the optical fluctuations by up to 25% below the vacuum level, in a bandwidth of about 15 kHz. Our results are explained well by a linearized dipole interaction between the nanoparticle and the electromagnetic continuum. These ponderomotive correlations open the door to quantum-enhanced sensing and metrology with levitated systems, such as force measurements below the standard quantum limit.
一个机械柔顺元件可以通过与光的相互作用而被驱动运动。反过来，这种光驱动运动能够在电磁场中产生光压关联。在光机械系统中，常常利用腔来增强这些关联，直至它们产生光的量子压缩。在未使用腔的自由空间情形中，虽然观察到压缩仍然是可能的，但由于相互作用较弱而颇具挑战性，并且迄今为止尚未有相关报道。在此，我们测量了由悬浮在自由空间光镊中的纳米粒子散射的光的光压压缩态。我们观察到在约15千赫兹的带宽内，光学涨落降低至比真空水平低达25%。我们的结果可以通过纳米粒子与电磁连续体之间的线性化偶极相互作用得到很好的解释。这些光压关联为利用悬浮系统进行量子增强传感和计量学开启了大门，例如进行低于标准量子极限的力测量。
