For the first time to our knowledge, the turbo-switched Mach–Zehnder interferometers (TS-MZIs) architecture, which includes quantum-dot semiconductor optical amplifiers (QDSOAs) and is followed by a series delayed interferometer (DI), is used in a combined scheme (QDSOAs-TS-MZIs-DI) to realise NOT-AND (NAND) and exclusive-NOR (XNOR) Boolean functions at a rate of 1 Tb/s return-to-zero data. The performance of the two considered gates is evaluated by calculating and comparing the quality factor and the cross-correlation coefficient for the QDSOAs-TS-MZIs-DI, the TS-MZIs with QDSOAs but without DI (QDSOAs-TS-MZIs) and the standard MZIs with QDSOAs (QDSOAs-MZIs). The comparison shows the superiority of the QDSOAs-TS-MZIs-DI over the other two alternatives (QDSOAs-TS-MZIs and QDSOAs-MZIs) and hence suggests that it should be preferred as a switching module when executing the NAND and XNOR Boolean functions at 1 Tb/s in the optical domain.