Shaping quantum system by indirect measurement

Quantum battery provides a paradigmatic example of reshaping the population distribution of an arbitrary quantum system. It aims to harness the unique properties of quantum mechanics to build a battery that is fundamentally different from the conventional one. In this work, we introduce a quantum-measurement scheme to charge a multilevel battery coupled to the ancillary systems. A measurement-based charging architecture is established based on a quantum collision model, whereby a battery in a thermal state could be transformed to a population-inverted state. It means that an energetic yet unusable system can be modified to be a state with a near-unit ratio of ergotropy (usable energy by unitary transformation) to energy. Our scheme connects the quantum thermodynamics far from equilibrium and quantum measurement.