A proposed method to measure weak magnetic field based on a hybrid optomechanical system

Enhancement of magnon-photon-phonon entanglement in a cavity magnomechanics with coherent feedback loop

In this paper, we present a coherent feedback loop scheme to enhance the magnon-photon-phonon entanglement in cavity magnomechanics. We provide a proof that the steady state and dynamical state of the system form a genuine tripartite entanglement state. To quantify the entanglement in the bipartite subsystem and the genuine tripartite entanglement, we use the logarithmic negativity and the minimum residual contangle, respectively, in both the steady and dynamical regimes. We demonstrate the feasibility of our proposal by implementing it with experimentally realizable parameters to achieve the tripartite entanglement. We also show that the entanglement can be significantly improved with coherent feedback by appropriately tuning the reflective parameter of the beam splitter and that it is resistant to environmental thermalization. Our findings pave the way for enhancing entanglement in magnon-photon-phonon systems and may have potential applications in quantum information.

Vibration induced transparency: Simulating an optomechanical system via the cavity QED setup with a movable atom

We simulate an optomechanical system via a cavity QED scenario with a movable atom and investigate its application in the tiny mass sensing. We find that the steady-state solution of the system exhibits a multiple stability behavior, which is similar to that in the optomechanical system. We explain this phenomenon by the opto-mechanical interaction term in the effective Hamiltonian. Due to the dressed states formed by the effective coupling between the vibration degree of the atom and the optical mode in the cavity, we observe a narrow transparent window in the output field. We utilize this vibration induced transparency phenomenon to perform the tiny mass sensing. We hope our study will broaden the application of the cavity QED system to quantum technologies.

Design and evaluation of magnetic field strength detection devices for millimeter-sized planar square inductors based on a mutual coupling model

Micro-magnetic stimulation is a research hotspot in the field of neuromodulation. However, it is difficult to measure the weak magnetic field produced by a millimeter-sized inductor. In this study, a mutual inductance model considering different positions and sizes was established for a common planar square spiral coil micro-magnetic stimulator. A physical model was simulated using the Comsol finite element method to verify the accuracy of the mutual inductance model. A weak magnetic field detection system was constructed using the TI AD8130 and NE5532 chips, and the magnetic field strengths of excitation micro-coils sized 3.612 × 3.612 and 5.55 × 5.55 mm² were measured. The results show that when the size ratio of the detection coil (DC) to the excitation coil (EC) is under a specific ratio (DC:EC = 1:1, 2:1, 1.53:1,2.36:1), the measurement range of the magnetic field strength is in the range 0-3.06 mT with an error of 0.05 mT, and the frequency is in the range 1-120 kHz. The measurement accuracy rate reaches 97.62%. The results of this study have potential application in the measurement of the weak magnetic field.

Stability of the Discrete Time-Crystalline Order in Spin-Optomechanical and Open Cavity QED Systems

Discrete time crystals (DTC) have been demonstrated experimentally in several different quantum systems in the past few years. Spin couplings and cavity losses have been shown to play crucial roles for realizing DTC order in open many-body systems out of equilibrium. Recently, it has been proposed that eternal and transient DTC can be present with an open Floquet setup in the thermodynamic limit and in the deep quantum regime with few qubits, respectively. In this work, we consider the effects of spin damping and spin dephasing on the DTC order in spin-optomechanical and open cavity systems in which the spins can be all-to-all coupled. In the thermodynamic limit, it is shown that the existence of dephasing can destroy the coherence of the system and finally lead the system to its trivial steady state. Without dephasing, eternal DTC is displayed in the weak damping regime, which may be destroyed by increasing the all-to-all spin coupling or the spin damping. By contrast, the all-to-all coupling is constructive to the DTC in the moderate damping regime. We also focus on a model which can be experimentally realized by a suspended hexagonal boron nitride (hBN) membrane with a few spin color centers under microwave drive and Floquet magnetic field. Signatures of transient DTC behavior are demonstrated in both weak and moderate dissipation regimes without spin dephasing. Relevant experimental parameters are also discussed for realizing transient DTC order in such an hBN optomechanical system.

Tunable high-order sideband generation in a coupled double-cavity optomechanical system

Tunable high-order sideband generation has important applications in the realization of the optical frequency comb with a varying spectral region (corresponding to the sideband range) and frequency resolution (corresponding to the sideband interval). In this paper, we propose a theoretical scheme to tune both the range and the interval of the high-order sidebands in a coupled double-cavity optomechanical system, which consists of an optomechanical cavity and an auxiliary cavity. Our proposal can be realized by driving the optomechanical cavity with a control field and a probe field simultaneously, driving the auxiliary cavity with a pump field. Furthermore, we assume that the frequency detuning between the control field and the probe field (the pump field) equals ω_b/n (ω_b/m), where ω_b is the mechanical frequency, m and n are integers. When n = m = 1, we find that the sideband range can be effectively enlarged by increasing the pump amplitude or the photon-hopping coupling rate, or by decreasing the auxiliary cavity damping rate. When n = 1 and m > 1, the output spectrum consists of a series of integer-order sidebands, fraction-order sidebands, and the sum and difference sidebands, and the sideband interval becomes ω_b/m and can be diminished by simultaneously increasing m and the pump amplitude.

Wide-range precision temperature measurement with optomechanically induced transparency in a double-cavity optomechanical system

This paper proposes a scheme for wide-range precision measurement of the environmental temperature in a double-cavity optomechanical system. This system consists of an optomechanical cavity coupling to the other cavity via photon tunneling interaction. Bycontrolling the tunnelling strength between the two cavities, double optomechanically induced transparency (double OMIT) effect is observed in the homodyne spetra of the outfield. It is shown that the central peak value depends linearly on the environmental temperature. Based on this linear relationship, the environmental temperature can be inferred from the central peak value of the output homodyne spectrum. This scheme is robust against mechanical decay and it shows high sensivity over a wide temperature range.

Highly Sensitive Charge Sensor Based on Atom-Assisted High-Order Sideband Generation in a Hybrid Optomechanical System

Realizing highly sensitive charge sensors is of fundamental importance in physics, and may find applications in metrology, electronic tunnel imaging, and engineering technology. With the development of nanophotonics, cavity optomechanics with Coulomb interaction provides a powerful platform to explore new options for the precision measurement of charges. In this work, a method of realizing a highly sensitive charge sensor based on atom-assisted high-order sideband generation in a hybrid optomechanical system is proposed. The advantage of this scheme is that the sideband cutoff order and the charge number satisfy a monotonically increasing relationship, which is more sensitive than the atom-free case discussed previously. Calculations show that the sensitivity of the charge sensor in our scheme is improved by about 25 times. In particular, our proposed charge sensor can operate in low power conditions and extremely weak charge measurement environments. Furthermore, phase-dependent effects between the sideband generation and Coulomb interaction are also discussed in detail. Beyond their fundamental scientific significance, our work is an important step toward measuring individual charge.

Two-color second-order sideband generation in an optomechanical system with a two-level system

Second-order sideband generation in an optomechanical system with the coupling between a mechanical resonator and a two-level system is discussed beyond the conventional linearized description of optomechanical interactions. The features of two-color second-order sideband generation are demonstrated in this hybrid system. We discovery that the switch between one- and two-color second-order sideband generation is easily realized by shifting the detuning between the control field and the cavity field or the transition frequency of the two-level system. The efficiency of two-color second-order sideband generation increases monotonously with the control field strength. The coupling strength between the mechanical resonator and the two-level system plays a decisive role in the appearance of the two-color second-order sidebands. The two-color second-order sideband generation may provide measurement with higher precision in new degrees of freedom.