Non-Markovian Charging of a Micromaser Quantum Battery

This paper investigates whether non-Markovian memory effects can be leveraged as a resource to improve the performance of quantum batteries (QBs). Specifically, the authors examine a Micromaser-based QB, where energy is stored in a resonant cavity mode, and explore how memory-assisted charging—where information from previous charging events is retained—affects energy storage capacity and stability.

To model the system, the authors employ a composite collisional model. In this setup, the battery (a quantum harmonic oscillator) interacts sequentially with a memory ancilla (a two-level system). This memory ancilla, in turn, interacts with a stream of external two-level chargers through partial swap interactions. By tuning the swap probability, the researchers can continuously interpolate between a memoryless (Markovian) regime and a strongly non-Markovian regime. They analyze the system's dynamics using numerical simulations, focusing on the energy stored in the battery and the associated energy fluctuations.

The study demonstrates that non-Markovian memory effects act as a beneficial resource. By retaining information from previous collisions, the memory ancilla forces the battery's steady-state population to localize near the upper boundary of the accessible Fock space. This results in higher steady-state energy storage and significantly suppressed energy fluctuations compared to the Markovian counterpart. The authors identify that intermediate values of the swap probability offer the best compromise between maximizing stored energy and maintaining reasonable charging speeds. Furthermore, they discuss how this scheme can be implemented in current circuit quantum electrodynamics (cQED) platforms using superconducting transmons.

This research provides a theoretical framework for optimizing quantum energy storage devices. By showing that environmental memory can be engineered to improve battery performance, the paper offers a path toward more reliable and efficient quantum thermodynamic devices. The proposed experimental implementation in superconducting circuits suggests that these theoretical advantages are within reach of current state-of-the-art quantum hardware.