No, it would only have a state. In classical physics the state would be its Kinetic energy. In QE it would be.... well it’s state. T is only defined in an ense

No, it would only have a state. In classical physics the state would be its Kinetic energy. In QE it would be.... well it’s state. T is only defined in an ensemble of other particles, i.e. when you can no longer keep track the particles and it’s necessary to use averages. Then the T is the average kinetic energy. Furthermore T is only technically defined in thermodynamic equilibrium, so nothing happens at all (otherwise you’re not in equilibrium). Finally, you can have “negative temperature” I.e T < absolute zero, if you have population inversion (I.e. a lasing cavity) which is really an abuse of nomenclature since population inversion cannot occur in equilibrium (and therefore T is not defined). However, the Boltzmann (?) equations have pop inv. only when the the T parameter is negative (even though pop inv. is the “hotter” than infinitely hot). All this to say that 1. T is not defined for a single particle 2. T is not well defined for very many systems at all!