Spin minimum uncertainty states for refined uncertainty relations

TL;DR

This paper explores the minimum uncertainty states in spin systems under an information-theoretic refinement of the Heisenberg relation, revealing known and new states that saturate the bound and comparing with bosonic systems.

Contribution

It derives explicit expressions for minimum uncertainty states in spin systems using two approaches and identifies new classes beyond coherent states.

Findings

Spin coherent states achieve minimum uncertainty.

Additional classes of minimum uncertainty states are identified.

Differences between spin and bosonic systems are elucidated.

Abstract

Minimum uncertainty states of the conventional Heisenberg uncertainty relation have been extensively studied and are often regarded as the most classical quantum states from the perspective of uncertainty, providing valuable insight into the nature of quantumness and its potential applications. In this work, we investigate the minimum uncertainty states associated with an information-theoretic refinement of the Heisenberg uncertainty relation in general spin systems. Using two different approaches, the matrix formulation and the Wick symbol representation, we derive explicit expressions for the states that saturate the uncertainty bound. We show that spin coherent states indeed achieve minimum uncertainty, consistent with their conventional identification as the classical states of spin systems. Moreover, we also identify additional classes of minimum uncertainty states beyond the coherent family. Finally, we compare the spin-system results with the previously studied bosonic case and elucidate the origin of the differences between the two settings.