Structured noise reveals hidden order in a small quantum experiment
A small experiment uses a tailored measurement strategy to examine mixed-state order.
Noise can produce a form of quantum order that ordinary measurements miss. A team using superconducting processors reports finite-size signatures of strong-to-weak spontaneous symmetry breaking, an effect in mixed quantum states that requires nonlinear diagnostics.[1][2]
The team prepared quantum states and collected measurements, then incorporated known dephasing probabilities during classical processing. That let it study many noise parameters using the same measured data. Two measurement settings reconstructed correlations that reveal hidden order alongside ordinary correlations that decay.[1][2]
The preprint was submitted on October 19. An October 20 QLab report says the experiment used access to IBM Heron processors and studied systems of no more than 12 .[1][2]
That system size should accompany any claim about the transition. The researchers report finite-size crossings and scaling behavior, rather than a direct experiment on an infinite system.[1][2]
The work also explores links between mixed-state order and the survival of encoded quantum information. It does not show that adding arbitrary noise improves a quantum computer.[1]