“…As a matter of fact, there are several problems of interest that are inherently involving more than one parameter [ 12 , 13 , 14 , 15 ], e.g. estimation of unitary operations and of multiple phases [ 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 ], estimation of phase and noise [ 27 , 28 , 29 , 30 ], and superresolution of incoherent sources [ 31 , 32 , 33 ].…”