Absence of local energy in elementary spin systems at low temperature

Local energy in a component of a multipartite quantum system is the maximum energy that can be extracted by a general (Kraus, operator-sum) local operation on just that component. A component’s local energy is greater or less, or even completely absent, depending on extant correlations with the system’s other components. This is illustrated in different cases of quantum systems of spin-1/2 particles. These cases include a class of two-particle systems with different degrees of coupling anisotropy, three-particle systems, and systems of N particles, generally, with ring and star coupling topologies. Conditions are given in each case for zero local energy. Th3ese conditions establish for each case that, fir systems with a non-degenerate entangled ground state, local energy is absent when the system state is anywhere in a neighborhood of the ground state when the temperature is below critical value in a Gibbs thermal state even systems of many particles.