Engineering squeezed thermal reservoirs via passive linear coupling

Squeezed thermal reservoirs, characterized by thermal noise with anisotropic fluctuations, have profound implications in quantum thermodynamics and serve as powerful resources for quantum information. However, their experimental realizations remain challenging. Existing schemes typically rely on injected squeezed light, time-dependent modulation, or driven nonlinear interactions, which introduce complexity and limit experimental feasibility. Using only time-independent linear coupling to a lossy mode within a normal thermal environment, we identify a general and experimentally accessible framework for squeezed-reservoir engineering, applicable across platforms such as circuit and cavity quantum electrodynamics as well as coupled cavity systems. We illustrate the framework through two experimentally relevant cases: directional phase coherence extension in two-level systems like qubits or atoms, and dissipative quadrature squeezing in bosonic modes like photons or phonons. By eliminating the need for active control or squeezed input, our passive linear-coupling approach provides a resource-efficient and practical pathway to dissipative squeezing, decoherence suppression, entanglement stabilization, quantum simulation, and the exploration of unconventional quantum thermodynamics and phase transitions.

💡 Research Summary

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The paper introduces a universal and experimentally friendly method for engineering squeezed thermal reservoirs without the need for external squeezed light, parametric drives, or time‑dependent modulation. The authors consider a generic system mode ( \hat s ) (which can be a two‑level qubit or a bosonic mode) linearly coupled to a lossy auxiliary bosonic mode ( \hat b ) that is itself damped into an ordinary thermal bath with mean occupation ( \bar n ) and decay rate ( \kappa ). The total Hamiltonian is bilinear, \