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.
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.
We study the directional phase-sensitive amplification between microwave and optical photons in a triple-cavity optomechanical system consisting of three cavities and one mechanical resonator. When the microwave cavity is pumped on both red and blue sidebands but the directly coupled optical cavities are only pumped on the red sidebands, directional phase-sensitive amplification can be realized by tuning the effective optomechanical couplings and the coupling strength between the optical cavities. We show that both gain and bandwidth of the amplifier can be enhanced by increasing the optomechanical cooperativities, indicating an unlimited gain-bandwidth product. Meanwhile, the proposed phase-sensitive amplifier can approach the quantum limit of zero added noise in the large cooperativity limit.
We theoretically propose a scheme for realizing a quantum-limited directional amplifier in a triple-cavity optomechanical system, where one microwave cavity and two optical cavities are, respectively, coupled to a common mechanical resonator. Moreover, the two optical cavities are coupled directly to facilitate the directional amplification between microwave and optical photons. We find that directional amplification between the three cavity modes is achieved with two gain process and one conversion process, and the direction of amplification can be modulated by controlling the phase difference between the field-enhanced optomechanical coupling strengths. Furthermore, with increasing the optomechanical cooperativity, both gain and bandwidth of the directional amplifier can be enhanced, and the noise added to the amplifier can be suppressed to approach the standard quantum limit on the phase-preserving linear amplifier.
Directional amplifiers are crucial nonreciprocal devices in both classical and quantum information processing. Here we propose a scheme for realizing a directional amplifier between optical and microwave fields based on an optomechanical system with optical gain, where an active optical cavity and two passive microwave cavities are coupled to a common mechanical resonator via radiation pressure. The two passive cavities are coupled via hopping interaction to facilitate the directional amplification between the active and passive cavities. We obtain the condition of achieving optical directional amplification and find that the direction of amplification can be controlled by the phase differences between the effective optomechanical couplings. The effects of the gain rate of the active cavity and the effective coupling strengths on the maximum gain of the amplifier are discussed. We show that the noise added to this amplifier can be greatly suppressed in the large cooperativity limit.
Abstract The investigation of the ultimate limits imposed by quantum mechanics on amplification represents an important topic both on a fundamental level and from the perspective of potential applications. We discuss here a novel regime for bosonic linear amplifiers—beside phase-insensitive and phase-sensitive amplification—which we term here phase-mixing amplification. Furthermore, we show that phase-mixing amplification can be realised in a cavity optomechanical setup, constituted by a mechanical resonator which is dispersively coupled to an optomechanical cavity asymmetrically driven around both mechanical sidebands. While, in general, this amplifier is phase-mixing, for a suitable choice of parameters, the amplifier proposed here operates as a phase-sensitive amplifier. We show that both configurations allow amplification with an added noise below the quantum limit of (phase-insensitive) amplification in a parameter range compatible with current experiments in microwave circuit optomechanics. In particular, we show that introducing phase-mixing amplification typically allows for a significant reduction of the added noise.
High-gain amplifiers of electromagnetic signals operating near the quantum limit are crucial for quantum information systems and ultrasensitive quantum measurements.However, the existing techniques have a limited gain-bandwidth product and only operate with weak input signals.Here, we demonstrate a two-port optomechanical scheme for amplification and routing of microwave signals, a system that simultaneously performs high-gain amplification and frequency conversion in the quantum regime.Our amplifier, implemented in a two-cavity microwave optomechanical device, shows 41 dB of gain and has a high dynamic range, handling input signals up to 10 13 photons per second, 3 orders of magnitude more than corresponding Josephson parametric amplifiers.We show that although the active medium, the mechanical resonator, is at a high temperature far from the quantum limit, only 4.6 quanta of noise is added to the input signal.Our method can be readily applied to a wide variety of optomechanical systems, including hybrid optical-microwave systems, creating a universal hub for signals at the quantum level.
Isolation of a system from its environment is often desirable; however, dissipation can also be a useful resource. Remarkably, engineered dissipation enables the preparation and stabilization of quantum states of atoms, ions or superconducting qubits. This is achieved by a suitably engineered coupling to a dissipative cold reservoir formed by electromagnetic modes. Similarly, in the field of cavity electro- and optomechanics the control over mechanical oscillators utilizes the inherently cold dissipative nature of the electromagnetic degree of freedom. Breaking from this paradigm, recent theoretical work has considered the opposite regime in which the dissipation of the mechanical oscillator dominates and provides a cold dissipative reservoir to the electromagnetic mode. Here we report the experimental realization of this reversed dissipation regime in a microwave cavity optomechanical system and realize a quasi-instantaneous, cold reservoir for microwave light. We evidence this regime by decreasing or increasing the damping rate of the cavity on demand, that corresponds to amplification and de-amplification of the microwave field. Additionally, we observe the onset of parametric instability, i.e. the stimulated emission of microwaves (masing). Moreover, we employ the engineered cold reservoir to implement a low-noise, large-gain phase-preserving amplifier. Beyond offering the manipulation of microwave fields, such a dissipative reservoir for microwave light, when coupled to multiple cavity modes, forms the basis of microwave entanglement schemes, electromechanical amplifiers with unlimited gain-bandwidth product and dissipative quantum phase transitions. Equally important, combining such reservoir-mediated interaction with coherent dynamics allows for the realization of non-reciprocal devices, which would extend the available toolbox of quantum-limited microwave manipulation techniques.