  Non-equilibrium fluctuation theorems (NFTs) relate work performed on a system
as its Hamiltonian varies with time, to equilibrium data of the initial and
final states. In a classical context the system energy can be directly
measured, while a quantum implementation requires the incorporation of a
work-agent. We demonstrate that the uncertainty principle imposes inherent
quantum limitations on the applicability of the NFT for probing non-trivial
mesoscopic systems. We work out the NFT validity regime for the simplest
quantum-dot toy model, and discuss future applications.
