Counterfactual universal quantum computation

TL;DR

This paper demonstrates that universal quantum computation can be achieved without direct interaction between quantum subsystems, introducing the concept of counterfactual quantum computation with practical considerations.

Contribution

It introduces the novel concept of counterfactual universal quantum computation, showing it is possible without initial interactions, and analyzes its feasibility with realistic devices.

Findings

Counterfactual communication of quantum states achieved

Counterfactual quantum swapping demonstrated

Analysis includes effects of photon loss and device imperfections

Abstract

Universal quantum computation is usually associated with interaction among two-level quantum subsystems, as this interaction is commonly viewed as a necessity to achieve universal quantum computation. In this work, we show that, contrary to this intuition, universal quantum computation can be achieved without interaction among initially independent two-level quantum subsystems. We call it counterfactual universal quantum computation. As special cases, we show how to achieve counterfactual communication of quantum states, counterfactual quantum swapping, and counterfactual quantum erasure codes. To ease practical implementation, we analyze counterfactual universal quantum computation with realistic devices, including the effects of finite execution time, photon loss, and atom missing. Besides the theoretical interest of illustrating the mysterious and counterintuitive nature of quantum physics, our work has practical applications to color imaging of ancient arts, upon which light is forbidden to shine.