JILA, National Institute of Standards and Technology and the University of Colorado, Boulder, Colorado 80309, USA and Department of Physics, University of Colorado, Boulder, Colorado 80309, USA.
Phys Rev Lett. 2018 Nov 2;121(18):183601. doi: 10.1103/PhysRevLett.121.183601.
We use the strong intrinsic nonlinearity of a microwave superconducting qubit with a 4 GHz transition frequency to directly detect and control the energy of a micromechanical oscillator vibrating at 25 MHz. The qubit and the oscillator are coupled electrostatically at a rate of approximately 2π×22 MHz. In this far off-resonant regime, the qubit frequency is shifted by 0.52 MHz per oscillator phonon, or about 14% of the 3.7 MHz qubit linewidth. The qubit behaves as a vibrational energy detector and from its line shape we extract the phonon number distribution of the oscillator. We manipulate this distribution by driving number state sensitive sideband transitions and creating profoundly nonthermal states. Finally, by driving the lower frequency sideband transition, we cool the oscillator and increase its ground state population up to 0.48±0.13, close to a factor of 8 above its value at thermal equilibrium. These results demonstrate a new class of electromechanics experiments that are a promising strategy for quantum nondemolition measurements and nonclassical state preparation.
我们利用一个具有 4GHz 跃迁频率的微波超导量子比特的强固有非线性，直接检测和控制以 25MHz 振动的微机械振荡器的能量。该量子比特和振荡器通过大约 2π×22MHz 的静电耦合。在这个远非共振的状态下，每个振荡器声子将量子比特频率移动 0.52MHz，大约是 3.7MHz 量子比特线宽的 14%。该量子比特表现为振动能量探测器，并且我们从其线形状中提取出振荡器的声子数分布。通过驱动数态敏感边带跃迁并创建深非热态，我们可以对其进行操纵。最后，通过驱动较低频率的边带跃迁，我们可以冷却振荡器并将其基态粒子数增加到 0.48±0.13，接近热平衡时值的 8 倍以上。这些结果展示了一类新的机电实验，它们是量子非破坏测量和非经典态制备的很有前途的策略。
