Fig. 1
From: Nondestructive detector for exchange symmetry of photonic qubits
a The principle of the controlled exchange interaction UF using three qubits. Two interacting qubits, a and b, are exchanged if and only if the controlling ancillary qubit m is in the state \(\left| 1 \right\rangle\). b The nondestructive detector of exchange symmetry (NDES) composed of the controlled exchange interaction device with the ancillary qubit m prepared in state \(\left| + \right\rangle\) and measured in the basis of \(\left| + \right\rangle\) and \(\left| - \right\rangle\). The qubits a and b are preserved and available for analyzing the influence of the device
