Improvement of the polarized neutron interferometer setup demonstrating violation of a Bell-like inequality

Abstract

For precise measurements with polarised neutrons high efficient spin-manipulation is required. We developed several neutron optical elements suitable for a new sophisticated setup, i.e., DC spin-turners and Larmor-accelerators which diminish thermal disturbances and depolarisation considerably. The gain in performance is exploited demonstrating violation of a Bell-like inequality for a spin-path entangled single-neutron state. The obtained value of S=2.365(13), which is much higher than previous measurements by neutron interferometry, is 280.25emσ above the limit of S=2 predicted by contextual hidden variable theories. The new setup is more flexible referring to state preparation and analysis, therefore new, more precise measurements can be carried out.

Classical Physics and the Bounds of Quantum Correlations

“…This represents a clear-cut violation of inequality (1), which is in agreement with the results obtained in experiments with two-photon states (e.g., E = 2.697 (15) [23]). Indeed, our result is closer to the quantum maximum, E = 2.828, than those from homologous experiments testing inequality (1) on singlephoton [E = 2.595(15) [24]] and single-neutron states [E = 2.365(13) [25]].…”

Additive-Manufactured and Topology-Optimized Permanent-Magnet Spin Rotator for Neutron Interferometry

“…Another crucial point is the thermal stability of the setup. A change of temperature during the measurement leads to a loss in contrast, as phase drifts occur, e.g., a temperature change of 1 • C results in 1.92 rad phase shift [33]. For this reason the Helmholtz coil Larmor spin-rotator is water-cooled ( Fig.…”

Fundamental Features of Quantum Dynamics Studied in Matter-Wave Interferometry—Spin Weak Values and the Quantum Cheshire-Cat

“…The obtained results of the measurements clearly show a violation of the Bell-like inequality. Afterwards, newly developed spin-rotators made it possible to obtain data with higher accuracy, which, in turn, offered a larger violation of the inequality [25]. In addition to that, a test of the Kochen-Specker theorem is carried out [26].…”

“…(ii) Weak interaction: Small spin rotations of α = ±15 deg are introduced by local modification of the static guide field. This is achieved by small coils aligned in a Helmholtz configuration and placed in boxes which are completely flooded with temperature controlled water [25]. As a result, the Larmor frequency is increased in path I and decreased in path II, leading to the different spin rotations of ± α in path I and in path II, respectively.…”