news & views coherent transfer determines the amount of no longer suitable for super-activation. states. Engineering different decay channels decoherence; the basis in which the qubit At one further point, they see that the should make it possible to observe a variety is dephased can be controlled using qubit entanglement and distillability with respect of entanglement progressions, which will manipulations performed before and after to all possible 2:2 partitions disappear give us further insights into the nature of the procedure. This engineered environment but those with respect to any of the 1:3 decoherence and entanglement4. Extending decoheres each qubit independently, but partitions are still present — this is the these techniques could also provide novel with the same strength. signature of bound entanglement. As methods for quantum state and process The team used quantum process more decoherence is introduced, the 1:3 engineering5,6, opening a new playground tomography to reconstruct the full entanglement also disappears, leaving a for quantum science. ❐ density matrix of the system for different fully separable state. values of applied decoherence. They Barreiro et al. harness state-of-the-art Jonathan Home is in the Institute for Quantum tested the density matrix for 1:3 and control for generation and manipulation Electronics, ETH Zurich, Hoenggerberg, Zurich 2:2 entanglement, for distillability, for of entangled states, and complement this 8093, Switzerland. violation of a Bell-like inequality and for with a rigorous theoretical analysis. The e-mail:
[email protected] its usefulness for ‘entanglement super- controlled progression of multipartite activation’ — a multi-party protocol similar entanglement is made possible by the References 3 to distillation .