Pre-management of disentanglement

We define threshold disentanglement as the level above which entanglement must be maintained for later use and calculate the values of quantum system parameters at t = 0 that will ensure that the threshold is not crossed in a specified time. An important issue is the possibility of non-smooth, typically non-exponential, decay of entanglement into the state of complete disentanglement. Given a specified operation time τ, we determine phase diagrams showing entanglement preservation during the evolution of a generic two-qubit mixed state as a function of selected initial parameters such as concurrence and excitation probabilities. In other words, disentanglement can be pre-managed through these parameters. Three common relaxation processes - amplitude, phase and depolarization - are considered.