Applied Physics, California Institute of Technology, Pasadena, CA 91125, USA. Kavli Nanoscience Institute, California Institute of Technology, Pasadena, CA 91125, USA.
Applied Physics, California Institute of Technology, Pasadena, CA 91125, USA. Department of Physics, University of Arizona, Tucson, AZ 85721, USA.
Science. 2014 Jun 13;344(6189):1262-5. doi: 10.1126/science.1253258. Epub 2014 May 15.
Quantum fluctuations of the light field used for continuous position detection produce stochastic back-action forces and ultimately limit the sensitivity. To overcome this limit, the back-action forces can be avoided by giving up complete knowledge of the motion, and these types of measurements are called "back-action evading" or "quantum nondemolition" detection. We present continuous two-tone back-action evading measurements with a superconducting electromechanical device, realizing three long-standing goals: detection of back-action forces due to the quantum noise of a microwave field, reduction of this quantum back-action noise by 8.5 ± 0.4 decibels (dB), and measurement imprecision of a single quadrature of motion 2.4 ± 0.7 dB below the mechanical zero-point fluctuations. Measurements of this type will find utility in ultrasensitive measurements of weak forces and nonclassical states of motion.
用于连续位置检测的光场量子涨落会产生随机反作用力，并最终限制灵敏度。为了克服这个限制，可以通过放弃对运动的完全了解来避免反作用力，这些类型的测量被称为“反作用规避”或“量子无损”检测。我们利用超导机电设备进行连续双音反作用规避测量，实现了三个长期目标：检测微波场量子噪声引起的反作用力，将这种量子反作用噪声降低 8.5 ± 0.4 分贝（dB），以及将运动的单个正交分量的测量不精确性降低 2.4 ± 0.7 dB，低于机械零点波动。这种类型的测量将在测量弱力和运动的非经典状态方面具有实用价值。
