Borromean Entanglement Revisited

An interesting analogy between quantum entangled states and topological links was suggested by Aravind. In particular, he emphasized a connection between the Greenberger-Horne-Zeilinger (GHZ) state and the Borromean rings. However, he made the connection in a way that depends on the choice of measurement basis. We reconsider it in a basis-independent way by using the reduced density matrix.