Universal state orthogonalizer and qubit generator

The superposition principle is at the heart of quantum mechanics and at the root of many para-doxes arising when trying to extend its predictions to our everyday world. Schrödinger’s cat [1] is the prototype of such paradoxes and here, in contrast to many others, we choose to investigate it from the operational point of view. We experimentally demonstrate a universal strategy for produc-ing an unambiguously distinguishable type of superposition, that of an arbitrary pure state and its orthogonal. It relies on only a limited amount of information about the input state to first generate its orthogonal one. Then, a simple change in the experimental parameters is used to produce arbi-trary superpositions of the mutually orthogonal states. Constituting a sort of Schrödinger’s black box, able to turn a whole zoo of input states into coherent superpositions, our scheme can produce arbitrary continuous-variable optical qubits, which may prove practical for implementing quantum technologies and measurement tasks. In the original Schrödinger’s cat paradox, an atom decaying into its ground state |0〉a causes a poisonous gas to be released, meaning the poison operation ÔP is performed. If th