Quantum fluid reveals hidden states that can be switched with a magnetic field
Bose-Einstein condensates (BECs) are often described as a “fifth state of matter”: a quantum state in which many particles lose their individual identities and behave as one collective object. For more than 60 years, researchers have sought to create such condensates from excitons—electron-hole pairs—as a solid-state route to macroscopic quantum coherence, which is useful for