“…It has been intensively studied at least during the last forty years, see for example [39], [19] and the references therein for more details. Among these works, some authors have established an intimate link between the existence of quadrature surfaces and the solution of free boundary problems governed by overdetermined partial differential equations, see for instance [25], [37], [38], [17] and references therein. The quadrature surface problem (2) can be tackled by a shape optimization approach when µ is regular enough, for instance by taking it in L 2 (Ω), supp(µ) ⊂ Ω. Fore more details see for instance [9] and [17].…”