Laboratoire de Physique Théorique
Toulouse - UMR 5152

Quantum-enhanced measurements use quantum mechanical effects to enhance the sensitivity of measurements. However, the required quantum states are generally highly entangled, difficult to produce, and very prone to decoherence. In work that has now appeared in Nature Communications, Daniel Braun of the LPT and John Martin (University de Liege) show how Heisenberg-limited measurements can be achieved without the use of entangled states by coupling the quantum resources to a common environment that can be measured at least in part. The method is robust under decoherence, and in fact the parameter dependence of collective decoherence itself can be used to reach Heisenberg-limited sensitivity.