Schrödinger's cat is a thought experiment designed to explain quantum superposition and quantum measurement, which are the core characteristics of quantum physics. In this experiment, the cat inside the box can be both alive and dead at the same time (quantum superposition), and its state (dead or alive) is decided the moment the box is opened (measured). Such quantum superposition and measurement are not only the foundation of quantum physics, but also guarantee the safety of quantum computing and cryptography.