  In the field of quantum metrology and sensing, a collection of quantum
systems (e.g. spins) are used as a probe to estimate some physical parameter
(e.g. magnetic field). It is usually assumed that there are no interactions
between the probe systems. We show that strong interactions between them can
increase robustness against thermal noise, leading to enhanced sensitivity. In
principle, the sensitivity can scale exponentially in the number of probes --
even at non-zero temperatures -- if there are long-range interactions. This
scheme can also be combined with other techniques, such as dynamical
decoupling, to give enhanced sensitivity in realistic experiments.
