On the Disentanglement of States

TL;DR

This paper investigates the limits of state disentanglement in quantum systems, proving that a universal disentangling machine cannot exist and identifying sets of states that cannot be disentangled.

Contribution

It introduces new results showing certain states cannot be disentangled, establishing fundamental limits on the possibility of universal quantum disentangling machines.

Findings

Some states cannot be disentangled into separable states

A universal disentangling machine is impossible

Disentanglement constraints depend on state properties

Abstract

Disentanglement is the process which transforms a state $\rho$ of two subsystems into an unentangled state, while not effecting the reduced density matrices of each of the two subsystems. Recently Terno showed that an arbitrary state cannot be disentangled into a tensor product of its reduced density matrices. In this letter we present various novel results regarding disentanglement of states. Our main result is that there are sets of states which cannot be successfuly disentangled (not even into a separable state). Thus, we prove that a universal disentangling machine cannot exist.