Experimental Virtual Quantum Broadcasting

TL;DR

This paper demonstrates the experimental realization of virtual quantum broadcasting using a nuclear magnetic resonance system, combining quantum circuits and post-processing to approximate ideal quantum state replication.

Contribution

It introduces an experimental implementation of virtual quantum broadcasting via a linear combination of unitaries, integrating physical channels with post-processing for improved fidelity.

Findings

Universal cloner closely approximates VQB.

Antisymmetrizer reduces broadcasting errors.

Method applicable to quantum systems of any dimension.

Abstract

The quantum no-broadcasting theorem states that it is fundamentally impossible to perfectly replicate an arbitrary quantum state, even if correlations between the copies are allowed. While quantum broadcasting cannot occur through any physical process, it can be achieved via postprocessing of experimental data using a process called virtual quantum broadcasting (VQB). In this work, we report the experimental implementation of a quantum circuit based on the linear combination of unitaries, integrated with a post-processing protocol, to realize VQB in a nuclear magnetic resonance system. VQB can be expressed as a linear combination of two channels: the universal cloner, which broadcasts the target quantum state, and the universal antisymmetrizer, which reduces broadcasting error. We implement both channels within the same circuit and demonstrate that the universal cloner is the closest physical map to VQB. In addition, we show how the universal antisymmetrizer can be utilized to mitigate imperfections in the cloner, enabling near-ideal fidelity. Our method is applicable to broadcasting quantum systems of any dimension.