Quantum mechanics sets a limit for the precision of continuous measurement of the position of an oscillator. We show how it is possible to measure an oscillator without quantum back-action of the measurement by constructing one effective oscillator from two physical oscillators. We realize such a quantum mechanics–free subsystem using two micromechanical oscillators, and show the measurements of two collective quadratures while evading the quantum back-action by 8 decibels on both of them, obtaining a total noise within a factor of 2 of the full quantum limit. This facilitates the detection of weak forces and the generation and measurement of nonclassical motional states of the oscillators. Moreover, we directly verify the quantum entanglement of the two oscillators by measuring the Duan quantity 1.4 decibels below the separability bound.

量子力学为振荡器位置连续测量的精度设定了极限。我们展示了如何通过从两个物理振荡器构造一个有效振荡器来测量没有量子反向作用的振荡器。我们使用两个微机械振荡器实现了这种无量子力学的子系统，并展示了两个集合正交的测量结果，同时对两个量子进行了8分贝的逃避量子反作用，从而获得了总噪声的2倍之内的总噪声。限制。这有利于弱力的检测以及振荡器的非经典运动状态的产生和测量。此外，我们通过测量在可分离性界限以下的1.4段分贝的段数来直接验证两个振荡器的量子纠缠。