Realization of a device-independent delayed-choice experiment using single photons

Wave-particle duality is one of the most intriguing features in quantum physics. A well-known gedanken experiment that provides evidence for this is the Wheeler's delayed-choice experiment based on a Mach-Zehnder interferometer. Many different versions of delayed-choice experiments have been conducted with both classical and quantum detecting devices. A recent proposal suggests that the delayed-choice experiment can be considered in the perspective of device-independent causal model. In this experiment, we realize this modified version with a deterministic single-photon source. Through our results, we can examine that any two-dimensional nonretrocausal classical model can be excluded in a device-independent manner based on the violation of dimension witness inequality. Our experiment also exhibits the benefits of studying quantum theory from the perspective of casual model.