Simulating all quantum measurements using only projective measurements and postselection

Understand

We report an alternative scheme for implementing generalized quantum measurements that does not require the usage of auxiliary system.

• Our method utilizes solely: (a) classical randomness and post-processing, (b) projective measurements on a relevant quantum system and (c) postselection on non-observing certain outcomes.
• The scheme implements arbitrary quantum measurement in dimension $d$ with the optimal success probability $1/d$.
• We apply our results to bound the relative power of projective and generalised measurements for unambiguous state discrimination.