An open quantum system is a quantum system studied together with its coupling to an external environment, rather than treated as perfectly isolated. That coupling lets energy and information flow between the system and its surroundings, producing decoherence and dissipation — effects a closed-system description, evolving only under its own Hamiltonian, cannot capture.
Most real quantum systems, including the ones a quantum computer or simulator is built from, are open systems in this sense, and their environment is usually treated as unwanted noise to suppress. But an open system’s environment can also be engineered on purpose — set to a target temperature or coupling strength — turning it into a controllable variable that lets a simulation reproduce how a real physical or chemical process actually behaves away from absolute zero.
Related papers
- So, Zhu, Duraisamy Suganthi, Menon, Tomaras, Zhuravel, Pu, and Pagano, “Experimental Realization of Thermal Reservoirs with Tunable Temperature in a Trapped-Ion Spin-Boson Simulator”, Physical Review Letters 137, 050604 (2026) — engineers the environment itself, rather than only suppressing it, to reach chosen finite temperatures. Covered in 2026-w32.