Diatomic molecule as a quantum entanglement switch

Abstract

We investigate a pair entanglement of electrons in diatomic molecule, modeled as a correlated double quantum dot attached to the leads. The low-temperature properties are derived from the ground state obtained by utilizing the Rejec-Ramsak variational technique within the framework of EDABI method, which combines exact diagonalization with ab initio calculations. The results show, that single-particle basis renormalization modifies the entanglement-switch effectiveness significantly. We also found the entanglement signature of a competition between an extended Kondo and singlet phases.Comment: To be presented on "The International Conference on Strongly Correlated Electron Systems" SCES'07, May 13-18, Houston, US

Pairwise entanglement and the Mott transition for correlated electrons in nanochains

“…For an open fermionic system (namely: acorrelated quantum dot attached to the leads) we found that the concurrence, defined separately for charge and spin degrees of freedom, allowed one to distinguish between different quantum transport regimes of the system [36]. Analogs of this observation were also reported for double [37,38] and triple quantum dots [39]. For closed systems, in particular for small molecules, Mottet et al [40] showed that the entanglement analysis provided a valuable insight into the chemical bond formation.…”

“…General findings, presented briefly in the above, are now illustrated with the numerical examples for N N el = and N N 2 el = (see figures 4 and 5). In both cases, the values of E v are close to the upper bounds given by equations (37) and (38) for the smallest considered value of R a 1.5 0 = , and systematically decrease with growing R, gradually approaching the lower bounds in equations (37) and (38). Also, a remarkably fast convergence of E v with growing N is observed for any R, making it necessary to apply vertical shifts to the datasets in figures 4 and 5.…”

“…In attempt to propose such correlation functions, one need to point out the relevance of quantum fluctuations between electronic doubly-occupied sites and unoccupied sites and between singly occupied sites with spin up and spin down in lattice models, as suggested before by numerous authors [15][16][17][18][19]. The concept quantum entanglement [20,21], together with entanglement measures such as the concurrence [22], was adopted to quantify the above-mentioned fluctuations in various systems [23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41], including basic spin models [23][24][25]42], fermionic systems [26][27][28][29][30][31], or systems with spin and orbital degrees of freedom [32][33][34][35]. For an open fermionic system (namely: acorrelated quantum dot attached to the leads) we found that the concurrence, defined separately for charge and spin degrees of freedom, allowed one to distinguish between different quantum transport regimes of the system [36].…”