Cooper-Pair Molasses: Cooling a nanomechanical resonator with quantum backaction

We have measured the back-action of a superconducting single electron transistor using a radio frequency nanomechanical resonator. The backaction forces are a factor of 15 above the intensity required by the Heisenberg uncertainty principle: $ \sqrt{S_x S_f}=15\frac{\hbar}{2} $. This system has also shown a record position and force sensitivity of $0.4fm/\sqrt{Hz}$ and $0.5aN/\sqrt{Hz}$, and the closest approach to the quantum ground state of a mechanical system (N=25) (1). In addition, we have discovered a novel cooling mechanism, analogous to optical molasses, which is a result of resonant Josephson effects in the transistor (2,3). Using devices of similar design and performance, we are anticipating the observation of squeezed, superposition, and entangled states of a mechanical device.\\ \\ 1. M.LaHaye, O. Buu, B. Camarota, K. Schwab, Science 304, 74 (2004). \\ 2. M. P. Blencowe, J. Imbers and A. D. Armour, xxx.lanl.gov/ cond-mat/0507645.\\ 3. A. A. Clerk, S. Bennett, xxx.lanl.gov/ cond-mat/0507646. \\