Knobel Robert G, Cleland Andrew N
Department of Physics and iQUEST, University of California, Santa Barbara, California 93106, USA.
Nature. 2003 Jul 17;424(6946):291-3. doi: 10.1038/nature01773.
It has been a long-standing goal to detect the effects of quantum mechanics on a macroscopic mechanical oscillator. Position measurements of an oscillator are ultimately limited by quantum mechanics, where 'zero-point motion' fluctuations in the quantum ground state combine with the uncertainty relation to yield a lower limit on the measured average displacement. Development of a position transducer, integrated with a mechanical resonator, that can approach this limit could have important applications in the detection of very weak forces, for example in magnetic resonance force microscopy and a variety of other precision experiments. One implementation that might allow near quantum-limited sensitivity is to use a single electron transistor (SET) as a displacement sensor: the exquisite charge sensitivity of the SET at cryogenic temperatures is exploited to measure motion by capacitively coupling it to the mechanical resonator. Here we present the experimental realization of such a device, yielding an unequalled displacement sensitivity of 2 x 10(-15) m x Hz(-1/2) for a 116-MHz mechanical oscillator at a temperature of 30 mK-a sensitivity roughly a factor of 100 larger than the quantum limit for this oscillator.
检测量子力学对宏观机械振荡器的影响一直是一个长期目标。振荡器的位置测量最终受量子力学限制，在量子基态下的“零点运动”涨落与不确定性关系相结合，从而对测量的平均位移产生下限。开发一种与机械谐振器集成且能接近这一极限的位置传感器，在检测极微弱力方面可能有重要应用，例如在磁共振力显微镜及各种其他精密实验中。一种可能实现接近量子极限灵敏度的方法是使用单电子晶体管（SET）作为位移传感器：利用SET在低温下极高的电荷灵敏度，通过电容耦合将其与机械谐振器相连来测量运动。在此，我们展示了这种器件的实验实现，对于一个116兆赫兹的机械振荡器，在30毫开尔文的温度下实现了2×10⁻¹⁵米×赫兹⁻¹/²的无与伦比的位移灵敏度，该灵敏度比该振荡器的量子极限大约高100倍。
