A which–way device is one which is designed to detect which of 2 paths is taken by a quantum particle, whether Schrödinger's cat is dead or alive. One possible such device is represented by an Aharonov–Bohm ring with a quantum dot on one branch. A charged cantilever or spring is brought close to the dot as a detector of the presence of an electron. The conventional view of such a device is that any change in the state of the cantilever implies a change in the electron state which will in turn destroy the interference effects. In this paper we show that it is in fact possible to change the state of the oscillator while preserving the quantum interference phenomenon.
Exploiting quantum interference presents a significant challenge in ultracold inelastic scattering. In this study we propose a method to verify quantum interference within the two-body loss rate that arises from multiple inelastic-scattering channels, where the colliding particles are initially prepared in their individual hyperfine states. Our approach employs a ring-coupling configuration, accomplished by combining external radio-frequency and static electric fields during ultracold atomic collisions. To validate our proposal, we perform close-coupling calculations for $^{7}\mathrm{Li}\text{\ensuremath{-}}^{41}\mathrm{K}$ collisions at the ultracold limit. The results reveal that the interference profile, as manifested in the two-body loss rate, can be verified with optimized external field parameters. Notably, our findings indicate that the two-body loss rate coefficient exhibits a distinct pattern of constructive or destructive interference when crossing a magnetically induced
p-wave resonance in the incoming channel. These interference patterns become increasingly pronounced as the intensities of the external fields increase. This work presents a potential approach to controlling inelastic-scattering processes in ultracold collisions.