You guessed it, diodes can also be used to build logic gates, but not all of them, only the AND and OR gates can be built using diodes only. However, by adding a transistor as an active element ...

Both diode gates use the diodes on their input lines, bringing the other ends of the diodes together at an output point with a pull-up or pull-down resistor. The diode OR gate has the anodes ...

7. A crude voltage multiplier. Use #2: Diode Logic Gates You can build simple logic gates using diodes. You can create an n-input OR gate or AND gate using 1 diode per input (Fig. 8). 8.