Taking accurate measurements of the temperature of quantum systems is a
challenging task. The mathematical peculiarities of quantum information make it
virtually impossible to measure with infinite precision. In the present letter,
we introduce a generalize thermal state, which is conditioned on the pointer
states of the available measurement apparatus. We show that this conditional
thermal state outperforms the Gibbs state in quantum thermometry. The origin
for the enhanced precision can be sought in its asymmetry quantified by the
Wigner-Yanase-Dyson skew information. This additional resource is further
clarified in a fully resource-theoretic analysis, and we show that there is a
Gibbs-preserving map to convert a target state into the conditional thermal
state. Finally, we relate the quantum J-divergence between the conditional
thermal state and the same target state to quantum heat.Comment: 5+6 pages, 2 figure