Quantum teleportation requires entanglement. The protocol is definitive: without entangled pairs shared between sender and receiver, teleportation fails. This has been shown theoretically and confirmed experimentally. Entanglement is the resource.
Chen et al. (arXiv:2602.01272) demonstrate teleportation-like remote imaging using pseudo-thermal light — classically correlated light with no entanglement whatsoever. The imaging protocol transmits the spatial pattern of an object at one location to a detector at another, using correlations in thermal photon fluctuations as the channel. The image appears at the receiver without the object's light ever reaching the receiver's detector.
The surprise: increasing the coherence of the light source — making it more laser-like, more orderly — degrades the image contrast. Better light produces worse images. The imaging quality peaks with maximally disordered (thermal) light and deteriorates as the light becomes more coherent.
The explanation identifies quantum discord, not entanglement, as the operating resource. Discord is a weaker-than-entanglement quantum correlation that exists even in classically correlated states. It measures the disturbance caused by measurement — the information destroyed when you observe one subsystem. Thermal light has high discord because measuring one photon's state strongly disturbs the correlated partner's conditional state. Coherent light has low discord because measurement barely disturbs anything — the photons are already in well-defined states.
The imaging protocol relies on this disturbance. The spatial pattern is encoded in how measurement at the object plane disturbs the correlations with the remote detector. More disturbance (higher discord) means more signal. Less disturbance (lower discord, higher coherence) means less signal. The “quantum” in the protocol is not entanglement but the measurement-induced disturbance that discord quantifies.
The structural lesson: entanglement is sufficient for teleportation-class protocols but not necessary. Discord — the asymmetry between classical and quantum conditional states — can serve as a substitute resource for tasks previously thought to require entanglement. The boundary between classical and quantum information processing is not entanglement but discord: a subtler, more pervasive form of quantum correlation.
Chen et al., "Discord-Enabled Teleportation-Inspired Optical Imaging at a Distance," arXiv:2602.01272 (2026).