Here we put forward a scheme for a quantum spin transistor that may serve as an integral component of quantum information devices. Similarly to the quantum computation proposals, it can be implemented with architectures that realize a Heisenberg spin chain. Various physical realizations of spin chains are being actively explored for short-range quantum state transfer required to integrate and scale-up quantum registers involving many qubits1112131415. In fact, spin chains of the Heisenberg type have been realized in organic and molecular magnets16, quantum dots17, various compounds161819, Josephson junction arrays20, trapped ions2122, in atomic chains on surfaces2324252627 and in thin films or narrow magnetic strips that carry spin waves2829. Combined with conditional dynamics implementing quantum logic gates, spin chains can greatly facilitate large-scale quantum information processing. While many different implementations of the coherent spin transistor may be possible, here we focus on one such proof-of-concept realization with a small ensemble of strongly interacting cold atoms trapped in a tight one-dimensional potential of appropriate shape. Cold atoms have already been used to realize spin chains, and observations of Heisenberg exchange dynamics30, spin impurity dynamics31 and magnon bound states32 have been reported.