Abstract The generation and robustness of two‐magnon non‐locality and coherence dynamics induced by an open microwave field cavity are investigated in this work. The studied system consists of a two‐sublattice ferrimagnet coupled to a microwave field within an open cavity through its magnetic field component. The robustness of the two‐magnons non‐locality dynamics is analyzed using various non‐locality and coherence measures (namely, uncertainty‐induced non‐locality [UIN], maximal Bell function, and log‐negativity entanglement [L‐NE]) in the presence of the spontaneous emission and the electromagnetic‐wave dissipation. It is shown that photon‐magnon couplings, two‐magnon couplings, and dissipation all have an impact on the dynamical aspect of two‐magnon non‐locality and coherence. This work reveals that the two‐magnon non‐locality and coherence can be generated. For an initial maximal correlated two‐magnon state, the initial UIN non‐locality is shown to be more resilient than the maximum Bell function and log‐negativity. The amplitudes of the two‐magnon non‐locality quantifiers decline as a result of the two‐magnon coupling. The Bell non‐locality and L‐NE are reduced via spontaneous emission and dissipation, but the two‐magnon UIN‐coherence is preserved. These findings contribute to a better understanding of such dynamics and may shed light on measurement estimation in open quantum systems.
Abstract The generation and robustness of two‐magnon non‐locality and coherence dynamics induced by an open microwave field cavity are investigated in this work. The studied system consists of a two‐sublattice ferrimagnet coupled to a microwave field within an open cavity through its magnetic field component. The robustness of the two‐magnons non‐locality dynamics is analyzed using various non‐locality and coherence measures (namely, uncertainty‐induced non‐locality [UIN], maximal Bell function, and log‐negativity entanglement [L‐NE]) in the presence of the spontaneous emission and the electromagnetic‐wave dissipation. It is shown that photon‐magnon couplings, two‐magnon couplings, and dissipation all have an impact on the dynamical aspect of two‐magnon non‐locality and coherence. This work reveals that the two‐magnon non‐locality and coherence can be generated. For an initial maximal correlated two‐magnon state, the initial UIN non‐locality is shown to be more resilient than the maximum Bell function and log‐negativity. The amplitudes of the two‐magnon non‐locality quantifiers decline as a result of the two‐magnon coupling. The Bell non‐locality and L‐NE are reduced via spontaneous emission and dissipation, but the two‐magnon UIN‐coherence is preserved. These findings contribute to a better understanding of such dynamics and may shed light on measurement estimation in open quantum systems.
In this paper, we explore distribution dynamics of two-qubit Fisher and skew information correlations of a dissipative microwave cavity field interacting with two charged superconducting qubits. Besides the negativity function, non-classical correlations beyond entanglement are studied using local quantum Fisher information (LQFI) and local quantum uncertainty (LQU). We find that the two-qubit non-classical correlations are sensitive to qubit–qubit distribution angle, two-qubit dissipation parameter, and initial coherent state intensity. The phenomena of frozen quantum correlations, sudden death or birth, as well as revival dynamical maps are feasible in the current two-qubit state when exposed to a microwave cavity. The non-classical correlations and entanglement have been found damped under the two-qubit dissipation appearance in the field. For the increasing strength of coherence intensity of the field, the two-qubit non-classical correlations functions remain to emerge quickly and oscillate with higher frequency, although with the least amplitudes. Interestingly, unlike the non-classical correlations, negativity does not emerge against higher coherence strengths of the cavity and remains completely zero. Finally, for the least dissipation and higher coherence strength, one can readily generate non-classical two-qubit states employing a microwave cavity.
Abstract This study is based on a theoretical proposal for quantum steering, non-locality, and entanglement in a two microwave cavities based magnomechanical system. The system is composed of two microwave (MW) cavity mode photons, phonons associated with mechanical mode and a magnon mode. We have employed a standard damping approach and found that steerability and entanglements among different bipartite subsystems strongly depend upon the detuning of indirectly coupled cavity mode and effective magnon detuning. One/two-way quantum Steering and non-local correlation have been found in the system for different choices of bipartitions. In addition, entanglement generated in the system enhances and has shown to be more robust against the thermal effects, as compared with the earlier studies. Interestingly, we have shown that the magnomechanical entanglements among different bipartitions have a complementary relation due to the transfer entanglement. This shows an additional insight into the system dynamics which shows that there exists a ‘tie-up’ relationship among these bipartitions. The present magnomechanical system will open new perspectives in quantum tasks that demand the entanglement of microwave cavity fields.
Abstract Entangled microwave fields are a crucial resource for quantum information processing and quantum computation. Here a scheme is presented to enhance quantum entanglement between two microwave cavity modes using coherent quantum feedback in cavity magnonics. The system consists of a planar cross‐line cavity that includes two microwave cavity modes, with a ferrimagnetic yttrium‐iron‐garnet (YIG) sphere positioned at the intersection of these modes. The magnon mode confined in the YIG sphere can simultaneously be coupled to both microwave cavity modes via magnetic dipole interaction. Additionally, a coherent feedback loop is integrated into one of the cavity modes to modulate its frequency detuning and dissipation. These results demonstrate that feedback control can effectively reduce the dissipation and effective environmental temperature, thereby relaxing the stringent requirement of quantum state generation on extremely low bath temperatures. Furthermore, by enhancing the feedback signal to reduce the high power requirement for activating magnon Kerr effect, the feasibility of the experiment is significantly improved. The scheme finds broad applications in many quantum tasks that require microwave entanglement and other research field that needs to cool quantum systems.
Dissipative coupling generally results in complex effective spin–photon interactions, which have significant applications in nonreciprocal transport and enhanced sensing technologies. In this paper, we consider the cooperative effect of coherent and dissipative magnon–photon couplings in an open cavity magnonical system. By enhancing the magnon Kerr nonlinearity with an additional microwave driving field, magnon-induced nonlinear phenomena such as bistability and second-order sideband generation (SSG) can be obtained. By continuously adjusting the ratio of dissipative to coherent coupling strengths, nonreciprocal SSG is observed near the zero-damping condition. Furthermore, the results show that the isolation ratio (the efficiency of the nonreciprocal SSG) can reach up to 82 dB. In addition, increasing the power of the microwave driving field broadens the control range of the dissipative coupling strength, within which the isolation ratio remains above 10 dB. These findings have potential implications for high-precision measurement and on-chip manipulation of light propagation.
Abstract This work delves into the nonlocal correlation dynamics of the maximum-Bell nonlocality (MBN), uncertainty-induced nonlocality (UIN), and concurrence of two two-level atoms having time-dependent atomic locations within Tavis-Cummings model. By considering a scenario where the pure two qubits resonantly interact with an even coherent cavity field through a two-photon transition, we explore the nonlocal correlation dynamics of both moving and stationary two-atom configurations under varying conditions and coupling parameters. Our findings reveal that the coherent cavity induces the successful generation of nonlocal correlations between atoms in both modes, with moving atoms exhibiting higher and symmetrical nonlocal correlations. Interestingly, dynamical maps showcase distinct behaviors for atoms at rest, exhibiting precocity at higher atom-cavity strengths. Moreover, equal coupling strength results in lower quantum correlations. The UIN measure emerges as the most robust quantum function, showing enhancements with sustained unequal coupling strengths, contrasting with the MBN and concurrence. These insights offer a nuanced understanding of nonlocal correlations in the Tavis-Cummings model, essential for advancing quantum information science and technology.
Quantum magnonics is an emerging research field, with great potential for applications in magnon based hybrid systems and quantum information processing. Quantum correlation, such as entanglement, is a central resource in many quantum information protocols that naturally comes about in any study toward quantum technologies. This applies also to quantum magnonics. Here, we investigate antiferromagnetic coupling of two ferromagnetic sublattices that can have two different magnon modes. We show how this may lead to experimentally measurable bipartite continuous-variable magnon-magnon entanglement. The entanglement can be fully characterized via a single squeezing parameter or, equivalently, entanglement parameter. The clear relation between the entanglement parameter and the Einstein, Podolsky, and Rosen (EPR) function of the ground state opens up for experimental quantification magnon-magnon continuous-variable entanglement and EPR nonlocality. We propose a practical experimental realization to measure the EPR function of the ground state, in a setting that relies on magnon-photon interaction in a microwave cavity.