The hybrid microwave optomechanical-magnetic system has recently emerged as a promising candidate for coherent information processing because of the ultrastrong microwave photon-magnon coupling and the longlife of the magnon and phonon. As a quantum information processing device, the realization of single excitation holds special meaning for the hybrid system. In this paper, we introduce a single two-level atom into the optomechanical-magnetic system and show that an unconventional blockade due to destructive interference cannot offer a blockade of both the photon and magnon. Meanwhile under the condition of single excitation resonance, the blockade of photon, phonon, and magnon can be achieved simultaneously even in a weak optomechanical region, but the phonon blockade still requires the cryogenic temperature condition.
We propose a scheme to generate strong squeezing of a mechanical oscillator in an optomechanical system through Lyapunov control. Frequency modulation of the mechanical oscillator is designed via Lyapunov control. We show that the momentum variance of the mechanical oscillator decreases with time evolution in a weak coupling case. As a result, strong mechanical squeezing is realized quickly (beyond 3 dB). In addition, the proposal is immune to cavity decay. Moreover, we show that the obtained squeezing can be detected via an ancillary cavity mode with homodyne detection.
Squeezing of quantum fluctuation plays an important role in fundamental quantum physics and has marked influence on ultrasensitive detection. We propose a scheme to generate and enhance the squeezing of mechanical mode by exposing the optomechanical system to a non-Markovian environment. It is shown that the effective parametric resonance term of mechanical mode can be induced due to the interaction with cavity and non-Markovian reservoir, thus resulting in quadrature squeezing of the mechanical resonator. And jointing the two kinds of interactions can enhance the squeezing effect. Comparing with the usual Markovian regime, we can obtain stronger squeezing, and significantly the squeezing can approach a low asymptotic stable value.Quantum physics exhibits many interesting non-calssical effects [1][2][3][4][5]. Quantum fluctuations, originated from the Heisenberg uncertainty principle, are the unique properties of quantum physics. Several well known interesting physical phenomena such as Casimir forces and the Lamb shift [6] are produced by quantum fluctuations. While quantum fluctuations also result in some restrictions in precision measurements. For example, the vacuum fluctuations in the optomechanical systems can broaden the optical response spectrum and affect the sensitivity of detection [7][8][9]. Fortunately, vacuum fluctuations are not immutable and can be 'squeezed' [10][11][12]. For a squeezed state, the quantum fluctuations in one variable are reduced below their value at the expense of the corresponding increased fluctuation in the conjugate variable [13]. By using the squeezing state, the precision of position measurement can be beyond the standard quantum limit [14]. Therefore, squeezed states of light are useful in high precision measurements such as gravitational wave detection [15,16].
In this paper we present an investigation of the ion currents produced by two different commercial RF (radio-frequency) plasma sources, detected at the position of a sample during growth. We have measured ion currents for a range of gas flow rates, plasma powers and Ar/N 2 gas compositions and found that the two sources behave very differently under the conditions investigated. We have demonstrated that the method described in this paper is a very efficient procedure for finding the optimal conditions for the growth of a high-quality material, and that the switching of N 2 into an Ar plasma is a viable technique for the growth of a dilute nitride material.
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