Decoherence and disentanglement for two qubits in a common squeezed reservoir

Abstract

We study the relation between the sudden death and revival of the entanglement of two qubits in a common squeezed reservoir, and the normal decoherence, by getting closer to the Decoherence Free Subspace and calculating the effect on the death and revival times.

Decoherence-free subspace and disentanglement dynamics for two qubits in a common non-Markovian squeezed reservoir

“…Let us recapitulate the observation made in Ref. [29] about the Markovian dynamics of entanglement for the state |Ψ 1 in the parameter interval 0 ≤ ǫ < 0.5 [see also the curve in dashed line in Fig. 1(a)], where it was shown that the initial entanglement decays to zero in a finite time t d .…”

“…Similar multiple death and revival cycle is observed for the state with ǫ = 0.5 in the non-Markovian case showing a clear departure from the Markovian dynamics. When 0.5 ≤ ǫ < 1, that is when we get closer to the Markovian DFS, it was shown [29] that the whole phenomenon of sudden death and revival disappears for the initial state |Ψ 1 . Contrary to that, we see [for the initial state |Ψ 1 with ǫ = 0.9 in Fig.1(c)] clear sudden death and revival for this range of ǫ as well in the non-Markovian case.…”

“…We vary ǫ between 0 and 1 for fixed values of the parameters r = 0.31 and θ = 0 as in Ref. [29]. Let us recapitulate the observation made in Ref.…”

“…The Markovian master equation, in the interaction picture, for two two-level systems interacting with a broadband squeezed vacuum bath (at zero temperature) is well studied [28][29][30] and is given by…”

“…3 in the next section. Now, in order to study the sudden death and revival of entanglement of two qubits in this common squeezed bath (both in the Markovian and non-Markovian regimes), we consider as initial states of the form [28,29] …”