Quantum systems tend to become less “quantum-y” as they interact with their environment. So when developing a mathematical description, it’s usually simpler just to view them as being closed off from their surroundings.

But ‘open’ systems are more realistic and sometimes even more interesting. Open quantum systems can be modelled using the so-called Lindblad equation, which describes the quantum evolution with time as both energy and coherence are lost to the environment.

Scientists from Tsinghua University have expanded the Lindblad equation to track the time evolution in an open system of a quantum property that that has become the hottest topic in condensed-matter physics: topology. Topology has formed the basis of numerous exotic states of matter over the last few decades. Now researchers show that an open system can undergo a topological transition as a result of dissipation, or loss.