Generalized interaction-free evolutions

Abstract

A thorough analysis of the evolutions of bipartite systems characterized by the 'effective absence' of interaction between the two subsystems is reported. First, the connection between the concepts underlying Interaction-Free Evolutions (IFE) and Decoherence-Free Subspaces (DFS) is explored, showing intricate relations between these concepts. Second, starting from this analysis and inspired by a generalization of DFS already known in the literature, we introduce the notion of generalized IFE (GIFE), also providing a useful characterization that allows to develop a general scheme for finding GIFE states.

Superradiant Quantum Phase Transition for an Exactly Solvable Two-Qubit Spin-Boson Model

“…We underline that, under the particular physical conditions in Equation ( 8), H b presents an effective decoupling of the fictitious two-level system b (which simulates the behaviour of the two actual spins within the subspace b) from the relative bosonic bath. This means that the subspace b is a decoherence-free subspace, or, in other words, that any initial state of the two-spin system belonging to such a subspace evolves as if the coupling between the two spins and the bath were absent [46][47][48]. The physical reason at the basis of this occurrence relies on the equal coupling of the two spins to the bath, i.e., c 1j = c 2j , ∀j.…”

Synchronizing Two Superconducting Qubits through a Dissipating Resonator

“…Basically, we look for a decoherence-free subspace [36,37]. In order to be insensitive to the noise, a quantum state should belong to the kernel of the dissipator (which implies it does not have a direct coupling to the environment) and to the kernel of the qubit-oscillator coupling (in order to avoid indirect coupling to the environment), thus obtaining a state that is interactionfree [38,39] with respect to the qubit-resonator coupling. By imposing the second condition,…”

Synchronizing two superconducting qubits through a dissipating resonator

“…Basically, we will look for a decoherence-free subspace [37,38]. In order to be insensitive to the noise, a quantum state should belong to the kernel of the dissipator (which implies it not to have a direct coupling to the environment) and to the kernel of the qubit-oscillator coupling (in order to avoid indirect coupling to the environment), thus obtaining a state which is interactionfree [39,40] with respect to the qubit-resonator coupling. By imposing the second condition,…”