Beyond qubits: Meet the qutrit (and ququart)

Researchers have demonstrated quantum error correction for qudits - systems that can hold more than two quantum states. They used a cavity connected to a transmon to create qutrits (3 states) and ququarts (4 states), showing error correction improved their longevity by about 1.8 times. This proof-of-principle work could help overcome hardware constraints in quantum computing by storing more information in less hardware.