A subsystem-independent generalization of entanglement.
We present a generalization of entanglement based on the idea that entanglement is relative to a distinguished subspace of observables rather than a distinguished subsystem decomposition. A pure quantum state is entangled relative to such a subspace if its expectations are a proper mixture of those of other states. Many information-theoretic aspects of entanglement can be extended to this observable-based setting, suggesting new ways of measuring and classifying multipartite entanglement. By going beyond the distinguishable-subsystem framework, generalized entanglement also provides novel tools for probing quantum correlations in interacting many-body systems.
Barnum
Howard
H
Los Alamos National Laboratory, MS B256, Los Alamos, New Mexico 87545, USA.
Knill
Emanuel
E
Ortiz
Gerardo
G
Somma
Rolando
R
Viola
Lorenza
L