Malz Daniel, Tóth László D, Bernier Nathan R, Feofanov Alexey K, Kippenberg Tobias J, Nunnenkamp Andreas
Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, United Kingdom.
Institute of Physics, École Polytechnique Fédérale de Lausanne, Lausanne 1015, Switzerland.
Phys Rev Lett. 2018 Jan 12;120(2):023601. doi: 10.1103/PhysRevLett.120.023601.
Directional amplifiers are an important resource in quantum-information processing, as they protect sensitive quantum systems from excess noise. Here, we propose an implementation of phase-preserving and phase-sensitive directional amplifiers for microwave signals in an electromechanical setup comprising two microwave cavities and two mechanical resonators. We show that both can reach their respective quantum limits on added noise. In the reverse direction, they emit thermal noise stemming from the mechanical resonators; we discuss how this noise can be suppressed, a crucial aspect for technological applications. The isolation bandwidth in both is of the order of the mechanical linewidth divided by the amplitude gain. We derive the bandwidth and gain-bandwidth product for both and find that the phase-sensitive amplifier has an unlimited gain-bandwidth product. Our study represents an important step toward flexible, on-chip integrated nonreciprocal amplifiers of microwave signals.
定向放大器是量子信息处理中的一种重要资源，因为它们能保护敏感量子系统免受过多噪声的影响。在此，我们提出一种在包含两个微波腔和两个机械谐振器的机电装置中实现用于微波信号的保相和相敏定向放大器的方案。我们表明两者都能在附加噪声方面达到各自的量子极限。在反向时，它们会发射源自机械谐振器的热噪声；我们讨论了如何抑制这种噪声，这对技术应用而言是一个关键方面。两者的隔离带宽约为机械线宽除以幅度增益。我们推导了两者的带宽和增益带宽积，发现相敏放大器具有无限的增益带宽积。我们的研究是朝着实现灵活的、片上集成的微波信号非互易放大器迈出的重要一步。
