Jain Vijay, Gieseler Jan, Moritz Clemens, Dellago Christoph, Quidant Romain, Novotny Lukas
Photonics Laboratory, ETH Zürich, 8093 Zürich, Switzerland.
Department of Physics and Astronomy, University of Rochester, Rochester, New York 14627, USA.
Phys Rev Lett. 2016 Jun 17;116(24):243601. doi: 10.1103/PhysRevLett.116.243601. Epub 2016 Jun 13.
The momentum transfer between a photon and an object defines a fundamental limit for the precision with which the object can be measured. If the object oscillates at a frequency Ω_{0}, this measurement backaction adds quanta ℏΩ_{0} to the oscillator's energy at a rate Γ_{recoil}, a process called photon recoil heating, and sets bounds to coherence times in cavity optomechanical systems. Here, we use an optically levitated nanoparticle in ultrahigh vacuum to directly measure Γ_{recoil}. By means of a phase-sensitive feedback scheme, we cool the harmonic motion of the nanoparticle from ambient to microkelvin temperatures and measure its reheating rate under the influence of the radiation field. The recoil heating rate is measured for different particle sizes and for different excitation powers, without the need for cavity optics or cryogenic environments. The measurements are in quantitative agreement with theoretical predictions and provide valuable guidance for the realization of quantum ground-state cooling protocols and the measurement of ultrasmall forces.
光子与物体之间的动量传递定义了物体可被测量的精度的基本极限。如果物体以频率Ω₀振荡，这种测量反作用会以速率Γ₍反冲₎向振荡器的能量中添加量子ℏΩ₀，这一过程称为光子反冲加热，并为腔光机械系统中的相干时间设定了界限。在此，我们在超高真空中使用光学悬浮纳米颗粒直接测量Γ₍反冲₎。通过一种相敏反馈方案，我们将纳米颗粒的简谐运动从环境温度冷却至微开尔文温度，并测量其在辐射场影响下的再加热速率。针对不同的颗粒尺寸和不同的激发功率测量了反冲加热速率，无需腔光学器件或低温环境。测量结果与理论预测在定量上相符，并为实现量子基态冷却协议和测量超小力提供了有价值的指导。
