Squeezing-Fueled Quantum Otto Engine via Measurement-Induced Cooling: The Two-Qubit Quantum Rabi Model

This paper investigates whether quantum resources—specifically cavity squeezing and measurement-induced cooling—can be integrated into a two-qubit quantum Rabi model to create a high-performance quantum Otto engine (QOE). The study aims to determine if these non-equilibrium resources can drive the engine's performance beyond the bounds typically imposed by conventional thermal reservoirs.

The researchers model a two-qubit system coupled to a single cavity mode within a cavity quantum electrodynamics (QED) architecture. The engine cycle consists of four strokes: non-adiabatic expansion, a hot isochoric stroke (modeled via the Hierarchical Equations of Motion, or HEOM, to capture non-Markovian system-bath correlations), a cooling stroke realized through projective measurements on the cavity, and a compression stroke. Squeezing is applied directly to the cavity mode as a fuel, and the authors derive analytical expressions for work and heat to quantify the engine's performance as a function of squeezing strength and phase.

The study reveals that cavity squeezing acts as a powerful thermodynamic resource. By tuning the squeezing phase, the engine can effectively function as a phase-sensitive thermal valve, allowing for the enhancement or reduction of heat absorption from the hot bath. The interplay between qubit-cavity coupling and measurement-induced cooling enables the engine to operate with efficiency that remains above the standard Otto bound, even as it approaches the limit-cycle regime. This architecture provides a concrete, experimentally realizable framework for thermodynamic optimization in cavity QED platforms.

This work advances the field of quantum thermodynamics by demonstrating that non-equilibrium quantum resources can replace traditional thermal baths. By utilizing measurement back-action and squeezing, the authors provide a pathway to design quantum heat engines that are not constrained by the limitations of conventional two-bath systems, offering new possibilities for energy management at the nanoscale.