I. Introduction
The Terahertz (THz) bands, from 0.1 THz to 10 THz, provide an abundance of bandwidth and are promising for enabling wireless links with extreme capacity in 2030 and beyond [1]. The sub-millimeter wavelength allows the incor-poration of hundreds and even thousands of low-gain antenna elements in compact arrays, leading to ultra-massive multiple-input multiple-output (UM-MIMO) systems. These systems establish highly directional links that efficiently combat severe signal attenuation in THz bands [2]. Furthermore, THz UM-MIMO systems can reach Tbps data rates and enable massive connectivity with beam steering [3].