Even in the presence of conservation laws, one can perform arbitrary transformations on a system if given access to a suitable reference frame, since conserved quantities may be exchanged between the system and the frame. Here we explore whether these quantities can be separated into different parts of the reference frame, with each part acting as a ‘battery’ for a distinct quantity. For systems composed of spin-1 particles, we show that the components of angular momentum Sx, Sy and Sz (non-commuting conserved quantities) may be separated in this way, and also provide several extensions of this result. These results also play a key role in the quantum thermodynamics of non-commuting conserved quantities.
Popescu, S., Sainz, A. B., Short, A. J., & Andreas, W. (2020). Reference frames which separately store noncommuting conserved quantities. Physical Review Letters, 125, . https://doi.org/10.1103/PhysRevLett.125.090601