Quantum-Limited Directional Amplifiers with Optomechanics

Abstract

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 and 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.Introduction.-Nonreciprocal transmission and amplification of signals are essential in communication and signal processing, as they protect the signal source from extraneous noise. Conventional ferrite-based devices rely on magnetic fields and are challenging to integrate in superconducting circuits. Hence, there exists strong incentive to find more suitable implementations [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. In the microwave domain, the strong Josephson nonlinearity and parametric pumping can achieve both photon gain and conversion processes, which have been exploited to realize circulators and directional amplifiers [5,[13][14][15]]. Another promising platform is optomechanics, where nonreciprocal devices [16][17][18][19][20][21][22][23][24][25][26][27], phase-preserving amplifiers [28][29][30][31][32], and phase-sensitive amplifiers [33][34][35][36] have been proposed and realized.In recent theoretical work, Ranzani and Aumentado [16,17] analyzed general conditions for nonreciprocity in parametrically coupled systems, and showed that nonreciprocity arises due to dissipation in ancillary modes and multi-path interference. Metelmann and Clerk [18] have shown that any coherent interaction can be made directional by balancing it with a dissipative process. Indeed, this insight led to a demonstration of nonreciprocity using optomechanics in the optical domain [19], and theoretical investigations into minimal implementations of directional amplifiers [20].While implementing the balance between a direct coherent coupling between the cavities and a dissipative interaction is challenging experimentally, Refs. [25][26][27] have recently studied and demonstrated nonreciprocal transmission between two cavity modes where two mechanical resonators each mediate both coherent and dissipative coupling. Here, building on this concept, we propose directional amplifiers using exclusively optomechanical interactions. Microwave tones on the red and blue sidebands enable so-called beam-splitter and two-mode squeezing interactions (cf. Fig. ...

Optimal control for feedback cooling in cavityless levitated optomechanics

“…The ability to precisely control and cool the motion of mechanical resonators in order to generate quantum states is of great interest for testing fundamental physics, such as investigating the quantum-to-classical transition [1,2]. A wide variety of resonator systems have shown promise for achieving such goals, including membranes [3,4], micro-and nano-resonators [5][6][7][8] and cantilevers [9,10]. Although ground state cooling has been experimentally realized in optomechanical systems [3,4,8], there is an appetite to reach such states in levitated systems.…”

Realization of Directional Amplification in a Microwave Optomechanical Device

“…Using two MOs, interference between the two paths allows for directional amplification of electromagnetic signals, realizing the scheme proposed in Ref. [39]. We further generalize the formalism of Ref.…”

“…We further generalize the formalism of Ref. [39] to include internal losses of the cavity modes present in the experiment. (a) Fourtone driving scheme.…”

Optimal unidirectional amplification induced by optical gain in optomechanical systems

“…For the first kind, the transmitted signal is the weak light field, and its transmis- * qz@gznu.edu.cn † liyong@csrc.ac.cn sion behavior is assisted by another strong control field which enhances significantly the effective optomechanical coupling. This kind of nonreciprocity has been achieved in physical systems displayed OMIT [16][17][18], frequency conversion between optical and microwave fields [19,20], and quantum-limited amplification [21][22][23][24][25][26][27][28][29][30]. And the second kind of optical nonreciprocity is based on the nonlinear interaction in the system, suggested in Ref.…”