Fig. 1: Schematic circuits of quantum controlled interferometers.
From: Experimental assessment of physical realism in a quantum-controlled device
The blue boxes represent unitary operations which here play the role of superposition devices---the quantum network equivalent of a beam-splitter. Using an ancillary qubit in superposition (quantum control system), we implement the quantumly controlled unitary superposition device (represented by the red boxes). a Original version of the quantum delayed-choice experiment, where the second beam-splitter is prepared in a coherent superposition of being in and out of the interferometer (configurations closed and open, respectively). b Our proposal for a quantum controlled reality experiment. Here, the first beam-splitter is submitted to quantum control. Although the measurement outcomes yield the same visibility in both of these experimental arrangements, the realism aspects inside the interferometer are crucially different.
