Low Temperature Laboratory, Aalto University, PO Box 15100, FI-00076 Aalto, Finland.
Nature. 2011 Dec 14;480(7377):351-4. doi: 10.1038/nature10628.
The sensitive measurement of electrical signals is at the heart of modern technology. According to the principles of quantum mechanics, any detector or amplifier necessarily adds a certain amount of noise to the signal, equal to at least the noise added by quantum fluctuations. This quantum limit of added noise has nearly been reached in superconducting devices that take advantage of nonlinearities in Josephson junctions. Here we introduce the concept of the amplification of microwave signals using mechanical oscillation, which seems likely to enable quantum-limited operation. We drive a nanomechanical resonator with a radiation pressure force, and provide an experimental demonstration and an analytical description of how a signal input to a microwave cavity induces coherent stimulated emission and, consequently, signal amplification. This generic scheme, which is based on two linear oscillators, has the advantage of being conceptually and practically simpler than the Josephson junction devices. In our device, we achieve signal amplification of 25 decibels with the addition of 20 quanta of noise, which is consistent with the expected amount of added noise. The generality of the model allows for realization in other physical systems as well, and we anticipate that near-quantum-limited mechanical microwave amplification will soon be feasible in various applications involving integrated electrical circuits.
电信号的灵敏测量是现代技术的核心。根据量子力学原理，任何探测器或放大器必然会给信号增加一定量的噪声，至少等于量子涨落所增加的噪声。超导器件利用约瑟夫森结的非线性，已经接近达到这种增加噪声的量子极限。在这里，我们引入了利用机械振荡放大微波信号的概念，这似乎有可能实现量子限制操作。我们利用辐射压力力驱动纳米机械谐振器，并提供了一个实验演示和分析描述，说明微波腔中的信号输入如何诱导相干受激辐射，从而导致信号放大。这种基于两个线性振荡器的通用方案在概念和实际方面都比约瑟夫森结器件更简单。在我们的设备中，我们通过添加 20 个量子噪声实现了 25 分贝的信号放大，这与预期的增加噪声量一致。该模型的通用性允许在其他物理系统中实现，我们预计，在涉及集成电路的各种应用中，接近量子限制的机械微波放大将很快成为可行的。
