In the present article we report the dynamical behavior of entanglement between π-electrons and photons in Graphene. It is shown that the degree of such entanglements depend on the orientation of πelectron momenta relative to the photonic polarization. Moreover, we show that as the detuning between the π-electron transition frequencies and that of the photons is increased, the degree of entanglement decreases.
In the present article we report the dynamical behavior of entanglement between π-electrons and photons in Graphene. It is shown that the degree of such entanglements depend on the orientation of πelectron momenta relative to the photonic polarization. Moreover, we show that as the detuning between the π-electron transition frequencies and that of the photons is increased, the degree of entanglement decreases.
In this paper, the mechanism of entanglement between electronic spin states and their spatial degrees of freedom in graphene is reported. From a calculation of the time evolution of von Neumann entropy, as a measure of entanglement, we show that the general behavior is oscillatory with characteristics depending on the external magnetic field, the Rashba spin–orbit coupling and the Landau states. The effect of these agents on the degree of entanglement is also discussed. It is shown that an increase in the magnetic field decreases the degree of entanglement, while an increase in Rashba spin–orbit coupling enhances the entanglement. Furthermore, for higher Landau levels the electronic states become more entangled. The material presented in this paper offers new means of controlling the entanglement of electronic states.
Abstract We investigate the dynamics of entanglement and quantum coherence between the pseudospin and valley indices of individual electrons in two-dimensional graphene, thermalized at an equilibrium temperature T . The system is modeled by an effective Dirac-like Hamiltonian describing a graphene valley-pseudospin qubit under polarized laser driving, including sublattice-dependent scattering process, while the thermal fluctuations are accounted through the standard Gibbs thermal state. Entanglement between the two degrees of liberty of electrons is quantified using concurrence, and coherence with the system is measured employing the relative entropy of coherence. The findings demonstrate that the behavior of entanglement and coherence under thermal noise strongly depends on the scattering strength, wavevector components, and electromagnetic field. Additionally, our results indicate that the strong polarized fields ( ξ 0 = 8 meV 2 ) with low-frequency ( ω = 0.06 eV ) can be employed to enhance the robustness of thermal entanglement and coherence of the system at intermediate temperatures. We also explore the impact of the other system parameters, like scattering strength and wavevector components, in enhancing and preserving quantum resources within graphene-based systems, noting particularly that the relative entropy of coherence is more resilient than concurrence against thermal decoherence.
Free entanglement—the milestone of any quantum information processing scheme—among the π -electronic spin and its spatial states in graphene, as a function of temperature, is the main concern of the present report. It is assumed that a perpendicular magnetic field generates the Landau levels so that a coupling with the pseudo-spin (sublattice) states is enacted. Moreover, the pseudo-Rashba spin–orbit interaction (SOI), responsible for the coupling of spin and sublattice states, is also taken into account. From the structure of the total Hamiltonian, we introduce a Casimir operator which, in due turn, assists the development of a simple but efficient algorithm for our numerical computation. We then proceed by constructing the thermal density operator, its partially transposed one and, thereby, compute the negativity, the proper measure of free hybrid entanglement, at any temperature. Our results show that the negativity is nonvanishing at absolute zero temperature due to the fact that the ground state is an entangled one. Moreover, our results indicate that the negativity, at certain temperatures, exhibits maxima. The temperatures at which the entanglement (free) is maximal strongly depend on the magnetic field and pseudo-Rashba spin–orbit strength; decreasing the magnetic field and/or increasing the pseudo-Rashba parameter (PRP) enhances the maximal entanglement monotonically. As the temperature increases, however, it is shown that the negativity decreases asymptotically to zero. As a result, there exists distillable entanglement amid the π -electronic spin and its spatial states in graphene at any finite temperature .
We studied the effects arising from a coherent source of photons on the entanglement between excitons in a strained graphene monolayer. The graphene layer was considered to be embedded in an imperfect optical microcavity. In our investigation, we have studied the entanglement dynamics of systems consisting of up to five excitons, which are treated as atomic-like qubits. Entangled states of multiple qubits are useful in quantum error correction codes. We have monitored the time evolution of the concurrence, three-π, mutual information, and especially the negativity. We have demonstrated that coherent pumping can create lasting entanglement between the excitons. However, the entanglement only persists when the rate at which photons are pumped is smaller than the decay rate of the cavity. Our results show that the degree in entanglement between the excitons is increased with the intensity of the strain-induced pseudomagnetic field in the graphene sheet. Additionally, we have shown that a maximum amount of entanglement occurs at a finite number of excitons in the system which depends on the parameters describing the structure.
Abstract We study the dynamics of entanglement between two edge spins in a zigzag graphene nanoribbon (ZGNR) which is thermalized with a reservoir at temperature T . The results show that the entanglement evolution displays oscillating behaviors in the presence of an external magnetic field. Such oscillating behaviors of entanglement strongly depend on the field frequency and relative location between two inter-edge coupled spins. At some critical field frequencies, the entanglement exhibits a periodic structure. When the temperature is low, the oscillating patterns of entanglement are quite regular and symmetrical. When the temperature is high, the patterns of entanglement evolution occur irregular distortions due to the thermal fluctuations. However, the entanglement between two inter-edge coupled spins in ZGNR still exists a nontrivial value even at room temperature.
Abstract This study explores the temporal evolution of local quantum Fisher information and coherence in a graphene monolayer subjected to a polarized electromagnetic field, revealing significant effects driven by system parameters. In the absence of the field, the analysis highlights the crucial role of the initial state's purity in the dynamics of both local quantum Fisher information and coherence, influencing their amplitude and decay over time. Introducing an electromagnetic field unveils a strong dependence of these quantities on the polarization and amplitude parameters. For linear polarization, local quantum Fisher information and coherence reach their maximum values at specific field phases, while for circular polarization, the system's response becomes more complex, exhibiting pronounced variations and a gradual decrease in coherence at higher field intensities. These findings emphasize the importance of controlling electromagnetic parameters to manipulate quantum information in graphene and open up new prospects for applications in quantum electronics and information processing.