Flowers-Jacobs N E, Schmidt D R, Lehnert K W
JILA, National Institute of Standards and Technology and the University of Colorado, Boulder, Colorado 80309, USA.
Phys Rev Lett. 2007 Mar 2;98(9):096804. doi: 10.1103/PhysRevLett.98.096804. Epub 2007 Mar 1.
We measure the noise added by an atomic point contact operated as a displacement detector. With a microwave technique, we increase the measurement speed of atomic point contacts by a factor of 500. The measurement is then fast enough to detect the resonant motion of a nanomechanical beam at frequencies up to 60 MHz and sensitive enough to observe the random thermal motion of the beam at 250 mK. We demonstrate a shot-noise limited imprecision of 2.3 fm/square root[Hz] and observe a 78 aN/square root[Hz] backaction force, yielding a total uncertainty in the beam's displacement that is 42 times the standard-quantum limit.
我们测量了用作位移探测器的原子点接触所添加的噪声。通过一种微波技术，我们将原子点接触的测量速度提高了500倍。这样一来，测量速度足够快，能够检测频率高达60 MHz的纳米机械梁的共振运动，灵敏度也足以观察到该梁在250 mK时的随机热运动。我们展示了2.3 fm/√Hz的散粒噪声限制不精确性，并观测到78 aN/√Hz的反作用作用力，这使得梁位移的总不确定度是标准量子极限的42倍。
