# Quantum gate
**Quantum gates** (or  **unitary quantum operators**) are the quantum computing equivalent of classical logic gates like "AND", "OR", "XOR", "NOT".

Classical logic gates are defined by their truth tables. They follow a mathematical structure called Boolean algebra. With the advancement of MOSFET transistor it became possible to implement these logic gates electrically. 

Quantum gates work in a similar way. They are defined by matrices. They follow the rules of a mathematical structure called the Lie group.