Excitonic entanglement of protected states in quantum dot molecules

Abstract

The entanglement of an optically generated electron-hole pair in artificial quantum dot molecules is calculated considering the effects of decoherence by interaction with environment. Since the system evolves into a mixed states and due to the complexity of energy level structure, we use the negativity as entanglement quantifier, which is well defined in $d \otimes d^\prime$ composite vector spaces. By a numerical analysis of the non-unitary dynamics of the exciton states, we establish the feasibility of producing protected entangled superpositions by an appropriate tuning of bias electric field, $F$. A stationary state with a high value of negativity (high degree of entanglement) is obtained by fine tuning of $F$ close to a resonant condition between indirect excitons. We also found that when the optical excitation is set approximately equal to the electron tunneling coupling, $\Omega/T_e \sim 1$, the entanglement reaches a maximum value. In front of the experimental feasibility of the specific condition mentioned before, our proposal becomes an useful strategy to find robust entangled states in condensed matter systems.Comment: 4 figure

Attractive Dipolar Coupling between Stacked Exciton Fluids

“…This charge separation induced by F z imparts very long lifetimes to the IXs, thus making them quasi-equilibrium excitations possessing a large dipole moment, which far exceeds the magnitude of atomic and molecular dipoles thus giving rise to strong inter-particle interactions [7,12]. The intra-DQW repulsive component has received considerable experimental attention in IX systems and was utilized for many opto-electronic functional demonstrations [13][14][15][16][17][18][19][20][21][22][23][24][25]. Furthermore, several many-body collective effects related to the bosonic character of these interacting particles have been reported [8][9][10][26][27][28][29][30][31][32].…”

Dynamic generation of GHZ states with coupled charge qubits

“…Quantum Dots (QDs) have been defined as artificial atoms, once the spatial confinement favors the formation of a discrete spectrum of electronic levels [11]. From all the possibilities of encoding a qubit, as in the excitonic states [12][13][14] and the electronic spin [15,16], the interest on the physics of charged quantum dots has been increasing, once they are scalable systems where initialization and readout are possible through a process involving detection even of a single electron [17,18]. In this physical system, the qubits are defined based on the property of electronic tunneling [7,19], with the singlequbit operations being controlled by external gate voltages [7,19].…”

Excitonic States and Photoluminescence Spectra of a Quantum Dot Molecule Exposed to the External Static Electric Field

“…Szafran et al studied the Stark effect for an exciton inside the quantum dot molecule for the electric field applied in the growth direction and for the electric field applied horizontally. The other effects, like the exciton fine structure, excitonic entanglement, trion states, and nonlinear effects are investigated both theoretically and experimentally.…”