Sumei Huang

In this paper, we propose a scheme where the charging performance of micromaser quantum batteries can be improved. Our physical system includes a quantized cavity field interacting with a series of identical two-level atoms one by one. In order to improve the performance of the battery, two methods are introduced: one is using a controlling field to drive atoms, and the other is placing OPA crystals in the cavity. Under these different methods, we discuss the influence of different parameters on battery capacity. Finally, combining the two methods for charging yields better results than using either of them alone. These protocols are found to be stable and robust, and most of the stored energy in the quantum batteries can be extracted for work. Our scheme has a potential applications in quantum energy storage devices.

The cooling of a macroscopic mechanical oscillator to its quantum ground state is an important step for achieving coherent control over mechanical quantum states. Here, we theoretically study the cooling of a rotating mirror in a Laguerre–Gaussian (L-G) cavity optorotational system with a nonlinear cross-Kerr (CK) interaction. We discuss the effects of the nonlinear CK coupling strength, the cavity detuning, the power of the input Gaussian beam, the topological charge (TC) of the L-G cavity mode, the mass of the rotating mirror, and the cavity length on the cooling of the rotating mirror. We find that it is only possible to realize the improvement in the cooling of the rotating mirror by the nonlinear CK interaction when the cavity detuning is less than the mechanical frequency. Compared to the case without the nonlinear CK interaction, we find that the cooling of the rotating mirror can be improved by the nonlinear CK interaction at lower laser powers, smaller TCs of the L-G cavity mode, larger masses of a rotating mirror, and longer optorotational cavities. We show that the cooling of the rotating mirror can be enhanced by the nonlinear CK interaction by a factor of about 23.3 compared to that without the nonlinear CK interaction.

Quantum entanglement is essential in performing many quantum information tasks. Here, we theoretically investigate the stationary entanglement between a Laguerre–Gaussian (LG) cavity field and a rotating end mirror in an LG-cavity optorotational system with a nonlinear cross-Kerr (CK) interaction and a degenerate optical parametric amplifier (OPA). We calculate the logarithmic negativity of the system to quantify the stationary entanglement. We examine the influence of various system parameters such as the cavity detuning, the strength of the nonlinear CK interaction, the parametric gain and phase of the OPA, the power of the input Gaussian laser, the topological charge of the LG-cavity field, the mass of the rotating end mirror, and the ambient temperature on the stationary entanglement. Under the combined effect of the nonlinear CK interaction and the OPA, we find that the stationary entanglement can be substantially enhanced at lower Gaussian laser powers, smaller topological charges of the LG-cavity field, and larger masses of the rotating end mirror. We show that the combination of the nonlinear CK interaction and the OPA can make the stationary entanglement more robust against the ambient temperature.

We study the propagation of a weak probe field through a dissipative optomechanical system, in which an additional weak mechanical drive is acting directly on a vibrating waveguide. In the presence of a strong coupling field, when the frequency of the mechanical drive precisely matches the frequency difference between the probe and coupling fields, we show that the nearly perfect absorption, complete transmission, and significant amplification of the probe field can be achieved by adjusting the amplitude and phase of the mechanical drive and the power of the coupling field. Moreover, by appropriately choosing the amplitude and phase of the mechanical drive, the group delay of the output probe field is tunable from a large negative value to a large positive value and vice versa. Our study offers an alternative way to control and manipulate the propagation of a weak probe field in a dissipative optomechanical system.

Quantum entanglement will play an important role in future quantum technologies. Here, we theoretically study the steady-state entanglement between a cavity field and a macroscopic rotating mirror in a Laguerre–Gaussian-(LG)-cavity optomechanical system with cross-Kerr nonlinearity. Logarithmic negativity is used to quantify the steady-state entanglement between the cavity and mechanical modes. We analyze the impacts of the cross-Kerr coupling strength, the cavity detuning, the input laser power, the topological charge of the LG-cavity mode, and the temperature of the environment on the steady-state optomechanical entanglement. We find that cross-Kerr nonlinearity can significantly enhance steady-state optomechanical entanglement and make steady-state optomechanical entanglement more robust against the temperature of the thermal environment.

Quantum entanglement in macroscopic systems plays an important role in quantum information processing. Here, we show that the steady-state entanglement between the two cavity modes in the macroscopic Laguerre–Gaussian (L–G) cavity optorotating system can be enhanced by placing a degenerate optical parametric amplifier (OPA) inside the cavity. The two L–G cavity modes are coupled to the same rotating mirror and are respectively driven at the red and blue mechanical sidebands. We use the logarithmic negativity to quantify the steady-state entanglement between the two cavity modes. We study the influences of the nonlinear gain and phase of the OPA, the temperature of the environment, and the angular momentums of the two cavity modes on the entanglement between the two cavity modes. In the cryogenic environment temperatures, when the angular momentums of the two cavity modes are identical, the enhancement of the entanglement between the two cavity modes by the OPA is the most significant.

The cavity magnomechanical system has become a promising platform for preparing macroscopic quantum states. In this work, a scheme for generating the steady‐state quadrature squeezing of the magnon and phonon modes in a cavity magnomechanical system is presented. This scheme uses a degenerate microwave parametric amplifier (PA) inside the microwave cavity. It is found that the squeezing of the cavity mode produced by the PA can be transferred to the magnon mode due to the cavity‐magnon beamsplitter‐like interaction, and the squeezing of the magnon mode can be further transferred to the phonon mode due to the magnon‐phonon beamsplitter‐like interaction induced by driving the magnon mode with a red‐detuned microwave field. The effects of the parametric gain and phase of the PA, the magnon‐cavity coupling strength, the power of the magnon drive, and the temperature of the environment on the squeezing of the magnon and phonon modes have been evaluated. The results show that the squeezing of the magnon and phonon modes is robust against the temperature of the environment.

In this paper, we studied the optomechanically induced transparency (OMIT) in a cavity optomechanical system containing a cubic nonlinear oscillator. In our system, a partially transparent, dielectric membrane was placed in the middle of the F-P cavity. Due to the partial transmission and reflective property of the membrane, the membrane was combined with both the mirrors on the left and right sides to form two cavities. When the system was driven by two coupling fields, we calculated the quantum fluctuation of the optomechanical system operators and showed the response of the cavity optomechanical system to the probe field. We found that the cubic nonlinearity led to a shift of the OMIT window, which moved towards a frequency less than the resonance frequency, and the absorption peak became significantly asymmetrical when OMIT appeared. The shift of the OMIT dip provided a method to detect the nonlinear effects of the system due to the existence of cubic anharmonic potential.

We study electromagnetically induced transparency (EIT) using quantized fields in a dissipative optomechanical system with two mechanical oscillators coupled to each other via the Coulomb interaction. The weak probe field is a finite bandwidth squeezed vacuum field. In the absence of the Coulomb coupling, we show that an EIT dip is observable in the homodyne spectrum of the output field even for the squeezed vacuum field at the single-photon level. We find that the thermal environment has a negative impact on the EIT behavior. In the presence of the Coulomb coupling, we show that double EIT dips appear in the homodyne spectrum of the output field. The separation between the two EIT dips can be used to measure the Coulomb coupling strength. Compared to the case of the purely dissipative coupling, the combined dispersive and dissipative coupling can make the EIT dip broader and the minimum value of the EIT dip smaller.

We study the cooling of a rotating mirror coupled to a Laguerre–Gaussian (L–G) cavity mode, which is assisted by an optical parametric amplifier (OPA). It is shown that the presence of the OPA can significantly lower the temperature of the rotating mirror, which is very critical in the application of quantum physics. We also find that the increase in angular momentum has an influence on the cooling of the rotating mirror. Our results may provide a potential application in the determination of the orbital angular momentum of light fields and precision measurement.