“…Among the systems modeled by quantum graphs are, e.g., electromagnetic optical waveguides [3,4], mesoscopic systems [5,6], quantum wires [7,8] and excitation of fractons in fractal structures [9,10]. Recent works have shown that quantum graphs provide an excellent system for studying quantum chaos [11][12][13][14][15][16][17][18][19][20][21]. Quantum graphs with external leads (antennas) have been analyzed in detail in [16,17].…”