Dynamics of two-level atoms (TLAs) above lossy graphene are studied using a master equation model, and improvement of entanglement compared to the vacuum case is demonstrated. Entanglement can be controlled by graphene biasing.
Using the quantum master equation, we demonstrate entanglement of two-level atoms (TLAs) over graphene. Graphene, acting as a structured photonic reservoir, significantly modifies the spontaneous decay rate of a TLA, and is rigorously incorporated into the formalism through the classical electromagnetic Green dyadic. Moreover, entanglement between the TLAs can be improved compared to the vacuum case, due to coupling of the TLAs to TM surface plasmons on graphene. Dynamics of TLAs can be further controlled by graphene biasing.
We explore the emergence and active control of optical bistability in a two-level atom near a graphene sheet. Our theory incorporates self-interaction of the optically driven atom and its coupling to electromagnetic vacuum modes, both of which are sensitive to the electrically tunable interband transition threshold in graphene. We show that electro-optical bistability and hysteresis can manifest in the intensity, spectrum, and quantum statistics of the light emitted by the atom, which undergoes critical slow-down to steady state. The optically driven atom-graphene interaction constitutes a platform for active control of driven atomic systems in coherent quantum control and atomic physics.
We investigate entanglement mediated by DC current induced nonreciprocal graphene plasmon polaritons. Nonreciprocal systems are ideal for the enhancement, control, and preservation of entanglement due to the potential for unidirectional beam-like wave propagation, i.e., efficiently transporting photons from one emitter to another. Using a quantum master equation and three-dimensional Green's function analysis, we investigate a system consisting of two two-level emitters dominantly interacting via electric current induced nonreciprocal plasmonic modes of a graphene waveguide. We use concurrence as a measure of entanglement. We show that nonreciprocal graphene plasmon polaritons are a promising candidate to generate and mediate concurrence, where it is shown that there is good enhancement and control of entanglement over vacuum, which is beneficial for the broad applications of entanglement as a quantum resource. We believe our findings contribute to the development of quantum devices, enabling efficient and tunable entanglement between two-level systems, which is a central goal in quantum technologies.
In this paper we investigated the entanglement dynamics of a pair of two-level atoms passing through a vacuum or thermal cavity one after another. We assumed that two atoms were initially prepared in separable coherent or entangled states. Using the exact solution of the density matrix evolution equation we calculated the time dependence of negativity for models with one-and two-photon interaction between atoms and the cavity field. For the two-photon model we took into account the dynamical Stark shift. We have found that the degree of atom-atom entanglement can be controlled by the Stark shift and cavity mean photon numbers.
The evolution of single particle excitations of bilayer graphene under effects of non-Markovian noise is described with focus on the decoherence process of lattice-layer (LL) maximally entangled states. Once the noiseless dynamics of an arbitrary initial state is identified by the correspondence between the tight-binding Hamiltonian for the AB-stacked bilayer graphene and the Dirac equation---which includes pseudovectorlike and tensorlike field interactions---the noisy environment is described as random fluctuations on bias voltage and mass terms. The inclusion of noisy dynamics reproduces the Ornstein-Uhlenbeck processes: A non-Markovian noise model with a well-defined Markovian limit. Considering that an initial amount of entanglement shall be dissipated by the noise, two profiles of dissipation are identified. On one hand, for eigenstates of the noiseless Hamiltonian, deaths and revivals of entanglement are identified along the oscillation pattern for long interaction periods. On the other hand, for departing LL Werner and Cat states, the entanglement is suppressed although, for both cases, some identified memory effects compete with the pure noise-induced decoherence in order to preserve the the overall profile of a given initial state.