Measuring Entanglement Using Quantum Quenches

We show that block entanglement entropies in one-dimensional systems close to a quantum critical point can, in principle, be measured in terms of the population of low-lying energy levels following a certain type of local quantum quench.

Figure 1

The action of a single twist operator on two one-dimensional systems with short-range interactions.

Figure 2

A single twist is equivalent to the closing of a point contact when $n$ is even and the ground state is invariant under reflection.