# Implementation of a two-qubit state by an auxiliary qubit on the three-spin system

## TL;DR

This paper proposes a method to prepare two-qubit entangled states using an auxiliary spin in a three-spin system, involving external magnetic fields and measurement, with practical implementation on xenon difluoride nuclear spins.

## Contribution

It introduces a novel protocol for entanglement generation in a three-spin system using an auxiliary spin and external control, applicable to nuclear spin systems.

## Key findings

- Conditions for achieving maximally entangled states are derived.
- Method demonstrated on xenon difluoride nuclear spins.
- Entanglement can be controlled via external magnetic fields and measurements.

## Abstract

The method for preparation of a two-qubit state on two spins-1/2 that mutually interact through an auxiliary spin is proposed. The essence of the method is that, initially, the three spins evolve under the action of an external magnetic field during a predefined period of time. Then, the auxiliary spin is measured by a monochromatic electromagnetic radiation that allows obtaining a certain state of the remaining spins. We study the entanglement of this state and obtain the condition for achieving the maximally entangled state. The implementation of the method on the physical system of nuclear spins of xenon difluoride is described. As a results, the conditions which allow preparing the maximally entangled state on this system are obtained.