Repeatedly measuring a quantum system can drastically change how it evolves. Studying spin chains under periodic monitoring, K. G. S. H. Gunawardana, Ali Moghaddam and Teemu Ojanen of QMAT's Theory of Quantum Matter group at Tampere University find two measurement-induced phase transitions.

One is the steady-state entanglement transition known from monitored quantum circuits. The other concerns how a domain wall between up and down spins melts: ballistically at low monitoring rates and diffusively at high rates. Simulations indicate that the two transitions are closely linked. Observing entanglement transitions requires exponentially costly postselection of measurement outcomes, whereas the ballistic–diffusive transition does not, making it an experimentally accessible manifestation of the many-body Zeno effect.

The preprint has not yet been peer reviewed.

Figure: Gunawardana et al., arXiv:2605.27350 (2026)