Reduced Khovanov homology detects the unknot among prime knots

Let $U$ denote the unknot, and let $K$ be a prime knot. Suppose that ${\widehat H}_{red}(K)$ and ${\widehat H}_{red}(U)$ are isomorphic as $\delta$-graded vector spaces over $\mathbb Z_2$. Reduced Khovanov unknot-detection conjecture. Then

$$K=U.$$

This conjecture asks whether reduced Khovanov homology detects the unknot when restricted to prime knots. The surrounding discussion presents it as a natural problem; no resolution is supplied here.