Decoherence of an entangled state of a strongly correlated double quantum dot structure through tunneling processes

Abstract

We consider two quantum dots described by the Anderson-impurity model with one electron per dot. The goal of our work is to study the decay of a maximally entangled state between the two electrons localized in the dots. We prepare the system in a perfect singlet and then tunnel-couple one of the dots to leads, which induces non-equilibrium dynamics. We identify two cases: if the leads are subject to a sufficiently large voltage and thus a finite current, then direct tunneling processes cause decoherence and the entanglement as well as spin correlations decay exponentially fast. At zero voltage or small voltages and beyond the mixed-valence regime, virtual tunneling processes dominate and lead to a slower loss of coherence. We analyze this problem by studying the real-time dynamics of the spin correlations and the concurrence using two techniques, namely the time-dependent density matrix renormalization group method and a master-equation method. The results from these two approaches are in excellent agreement in the direct-tunneling regime for the case in which the dot is weakly tunnel-coupled to the leads. We present a quantitative analysis of the decay rates of the spin correlations and the concurrence as a function of tunneling rate, interaction strength, and voltage.

Dynamics of non-Markovian open quantum systems

“…Shabani and Lidar (2009) proposed that quantum discord is not only sufficient, but also necessary for CP dynamics. Later, Brodutch et al (2013) and Buscemi (2014) showed that complete positivity may also be fulfilled for some particular states with nonvanishing quantum discord, i.e. including quantum correlations [see also (Shabani and Lidar, 2016)].…”