The lossy one-helper conjecture is false

We describe a scheme for rate-distortion with distributed encoding in which the sources to be compressed contain a common component. We show that this scheme is optimal in some situations and that it strictly improves upon existing schemes, which do not make full use of common components. This resolves in the negative an open question regarding whether independent quantization followed by independent binning is optimal for the two-encoder problem with a distortion constraint on one source. We also show that independent quantization and binning is suboptimal for the three-encoder problem in which the goal is to reproduce one of the sources losslessly. This provides a counterexample that is fundamentally different from one provided earlier by Körner and Marton. The proofs rely on the binary analogue of the entropy power inequality and the existence of a rate loss for the binary symmetric Wyner-Ziv problem.