Violation of Heisenbergs error-disturbance relation by Stern-Gerlach measurements

Although Heisenbergs uncertainty principle is represented by a rigorously proven relation about intrinsic indeterminacy in quantum states, Heisenbergs error-disturbance relation (EDR) has been commonly believed as another aspect of the principle. However, recent developments of quantum measurement theory made Heisenbergs EDR testable to observe its violations. Here, we study the EDR for Stern-Gerlach measurements. In a previous report [arXiv:1910.07929], it has been pointed out that their EDR is close to the theoretical optimal. The present note reports that even the original Stern-Gerlach experiment in 1922, the available experimental data show, violates Heisenbergs EDR. The results suggest that Heisenbergs EDR is more ubiquitously violated than it has long been supposed.