# Molecular quantum spin network controlled by a single qubit

## TL;DR

This paper demonstrates a molecular quantum spin network controlled by a single NV center, using spin-labeled peptides to enable scalable quantum information processing and molecular mapping.

## Contribution

It introduces a molecular building block for quantum networks, controlled and read out via NV centers, combining chemistry and quantum technology for scalable quantum systems.

## Key findings

- Coherent manipulation of up to 6 electron spins in a molecular network.
- Access to the dipolar coupling tensor of the spins.
- Feasibility of using spin-labeled peptides for quantum networks.

## Abstract

Scalable quantum technologies will require an unprecedented combination of precision and complexity for designing stable structures of well-controllable quantum systems. It is a challenging task to find a suitable elementary building block, of which a quantum network can be comprised in a scalable way. Here we present the working principle of such a basic unit, engineered using molecular chemistry, whose control and readout are executed using a nitrogen vacancy (NV) center in diamond. The basic unit we investigate is a synthetic polyproline with electron spins localized on attached molecular sidegroups separated by a few nanometers. We demonstrate the readout and coherent manipulation of very few ($\leq 6 $) of these $S=1/2$ electronic spin systems and access their direct dipolar coupling tensor. Our results show, that it is feasible to use spin-labeled peptides as a resource for a molecular-qubit based network, while at the same time providing simple optical readout of single quantum states through NV-magnetometry. This work lays the foundation for building arbitrary quantum networks using well-established chemistry methods, which has many applications ranging from mapping distances in single molecules to quantum information processing.