Subadditivity of Von Neumann entropy
= Subadditivity of Von Neumann entropy
{c}
For a bipartite <density operator> $\rho_{AB}$,
$$
S(\rho_{AB})\leq S(\rho_A)+S(\rho_B).
$$
Equality holds exactly when $\rho_{AB}=\rho_A\otimes\rho_B$.
= Subadditivity of Von Neumann entropy
{c}
For a bipartite <density operator> $\rho_{AB}$,
$$
S(\rho_{AB})\leq S(\rho_A)+S(\rho_B).
$$
Equality holds exactly when $\rho_{AB}=\rho_A\otimes\rho_B$.