We investigate theoretically macroscopic quantum coherence and tripartite entanglement in a three-mode magnomechanical system with a yttrium iron garnet sphere, which is simultaneously driven by a magnetic pump and a microwave field pump to establish an effective magnomechanical coupling. We discuss mainly the dependence of quantum properties on the driving power, the cavity field detuning and decay, the magnomechanical coupling strength, the bias magnetic field, and the temperature of an environment. It is found that the quantum coherence of the system can be attained easily in a large range of parameters. In contrast, tripartite photon-magnon-phonon entanglement can only be realized in a relatively small range of optical and magnetic parameters. In particular, the quantum coherence of the mechanical mode can be larger than that of the photon and magnon modes, which means that the environmental incoherence of the mechanical mode in the cavity magnomechanical system can be suppressed significantly. These results may help manipulate simultaneously the macroscopic quantum coherence and the tripartite entanglement of massive objects in coupled magnomechanical system, which may have potential applications for realizing highly tunable information processing through the flexible control of quantum properties.

The germinal center (GC) reaction underlies productive humoral immunity by orchestrating competition-based affinity maturation to produce plasma cells and memory B cells. T cells are limiting in this process. How B cells integrate signals from T cells and BCRs to make fate decisions while subjected to a cyclic selection process is not clear. In this article, we present a spatiotemporally resolved stochastic model that describes cell behaviors as rate-limited stochastic reactions. We hypothesize a signal integrator protein integrates follicular helper T (Tfh)- and Ag-derived signals to drive different B cell fates in a probabilistic manner and a dedicated module of Tfh interaction promoting factors control the efficiency of contact-dependent Tfh help delivery to B cells. Without assuming deterministic affinity-based decisions or temporal event sequence, this model recapitulates GC characteristics, highlights the importance of efficient T cell help delivery during individual contacts with B cells and intercellular positive feedback for affinity maturation, reveals the possibility that antagonism between BCR signaling and T cell help accelerates affinity maturation, and suggests that the dichotomy between affinity and magnitude of GC reaction can be avoided by tuning the efficiency of contact-dependent help delivery during reiterative T–B interactions.

A proper description of spin glass remains a hard subject in theoretical physics and is considered to be closely related to the emergence of chaos in the renormalization group (RG) flow. Previous efforts concentrate on models with either complicated or nonrealistic interactions in order to achieve this chaotic behavior. Here we find that the commonly used Potts model with long-range interaction could do the job nicely in a large parameter regime as long as the competition between the ferromagnetic and antiferromagnetic interaction is maintained. With this simplicity, the appearance of chaos is observed to sensitively depend on the detailed network structure: the parity of bond number in a branch of the basic RG substituting unit; chaos only emerges for even numbers of bonds. These surprising and universal findings may shed light on the study of spin glass.

We theoretically investigate the macroscopic quantum coherence and the mechanical squeezing of a mechanical oscillator in a hybrid optomechanical system consisting of a suspended graphene sheet and an ultracold atomic ensemble trapped inside a Fabry-Pérot cavity. In the study the vacuum is used to mediate an effective optomechanical coupling between the graphene oscillator and the cavity field driven by an external laser beam. We find that in the presence of this coupling, the macroscopic quantum coherence and the mechanical squeezing of the graphene sheet can be attained in a certain range of driving power. In particular, the quantum coherence in the optomechanical system can be transferred from the optical field to the mechanical oscillator. We also investigate in detail the spectrum and the squeezing of the output field and the attained results may be used to study the mechanical squeezing of a graphene sheet.

We investigate thermo-phonon transport and its nontrivial Berry-phase-like effect in an optomechanical system with a squeezed vacuum injection. By taking the cumulant generation function approach the exact expressions of the thermo-phonon flux and optomechanical Berry phase are derived analytically. Further, the quantum master equation approach is invoked to verify the analytical results of the transport properties. It is shown that the steady-state thermo-phonon flux can be modulated by varying optically the nonequilibrium characteristics of the system via the squeezed vacuum. In particular, an adiabatic modulation of squeezing parameters induces an optomechanical Berry-phase-like effect and as a result provides an additional geometric phonon response across the macroscopic mechanical motion near the quantum regime, which can also be seen as a consequence of the asymmetric jumping probability between transition associated with phonon absorption and emission in a thermal bath. The present method and results are general and can be straightforwardly extended to any multimode oscillator systems and therefore pave the way to the thermal noise energy harvesting and rectification in coupled oscillator systems with inertial terms.

We propose theoretically a four-mode coupled optomechanical system to explore the optical-response properties of an optical trimer system consisting of a passive cavity, a no-loss-gain cavity, and an active cavity coupled with a mechanical oscillator. In the study, the passive cavity is driven by an external laser so that the stability of the coupled system depends strongly on the gain-to-loss ratio and the photon tunneling between the adjacent cavities. We find that in the regime near the stable-unstable critical point, the resonance absorption of the optical trimer system changes quickly with the increasing gain of the active cavity. In contrast, when the mechanical oscillator is coupled to the passive cavity, the center absorption peak is split and a phenomenon of optomechanically induced transparency appears. Consequently, two additional resonance peaks in the absorption profile are induced by the optomechanical coupling, which hinges on the tunneling between the optical cavities and also on the gain of the active cavity. The dependence of the width of the transparency window on the optomechanical coupling and the driving strength is also discussed in detail. The results obtained here indicate that the optical properties of the trimer system can be manipulated by coupling a mechanical oscillator to the system and therefore have a potential application in quantum optics and quantum information processing.