01551nas a2200157   4500000000100000000000100001008004100002100002200043700002200065700002200087245009300109856003900202300001100241490000800252520113300260       2019                            d1 aMichał Oszmaniec1 aFilip Maciejewski1 aZbigniew Puchała00aSimulating all quantum measurements using only projective measurements and postselection  uhttps://arxiv.org/abs/1807.08449v1  a0123510 v1003 a<p>Implementation of generalized quantum measurements is often experimentally demanding, as it requires performing a projective measurement on a system of interest extended by the ancilla. We report an alternative scheme for implementing generalized measurements that uses solely: (a) classical randomness and post-processing, (b) projective measurements on a relevant quantum system and (c) postselection on non-observing certain outcomes. The method implements arbitrary quantum measurement in d dimensional system with success probability 1/d. It is optimal in the sense that for any dimensionn d there exist measurements for which the success probability cannot be higher. We apply our results to bound the relative power of projective and generalised measurements for unambiguous state discrimination. Finally, we test our scheme experimentally on IBM quantum processor. Interestingly, due to noise involved in the implementation of entangling gates, the quality with which our scheme implements generalized qubit measurements is higher than the one obtained with the standard construction using the auxiliary system.</p>