Closed-Form Expressions for Two- and Three-Colorable States

Graph states are a class of multi-partite entangled quantum states, where colorability, a property rooted in their mathematical foundation, has significant implications for quantum information processing. In this study, we investigate the colorability of graph states in qudit systems to simplify their representation and enhance their practical applications. We present closed-form expressions for all two-colorable graph states. Our findings show that the closed-form expression of these states is tightly linked to the graph structure and the distribution of particles in red ($n_R$) and blue ($n_B$). Additionally, we explore a broad family of three-colorable graph states constructed from two two-colorable graph states. The closed-form expression for these states is in the form of one two-colorable state tensor product with the graph basis formed from another two-colorable state. Our approach systematically reduces the number of terms required to represent these states. Furthermore, we demonstrate that many well-known mathematical graphs, including friendship graphs, fit within our formalism. Finally, we discuss the LU/SLOCC (Local Unitary/Stochastic Local Operation and Classical Communication) equivalence between two- and three-colorable graph states. Our findings have broad implications for characterizing the LU/SLOCC equivalence of graph state classes and pave the way for future research.