A quantum vortex is a phenomenon that occurs in superfluid helium and other quantum fluids, where the fluid exhibits a swirling motion at a microscopic scale. In this state, the fluid can flow without viscosity, allowing it to create stable, quantized vortices. These vortices are characterized by a core region where the fluid's density is lower, surrounded by a rotating flow. In the context of quantum mechanics, quantum vortices provide insights into the behavior of matter at extremely low temperatures. They are essential for understanding superconductivity and superfluidity, as they reveal how particles interact and organize themselves in a quantum state.