# Entangling two atoms of different isotopes via Rydberg blockade

## TL;DR

This paper demonstrates the first experimental entanglement of two different isotope neutral atoms using Rydberg blockade, enabling advanced quantum simulations and computing with multi-species systems.

## Contribution

It reports the first realization of heteronuclear entanglement between different isotope neutral atoms, including a heteronuclear C--NOT gate and entangled state with high fidelity.

## Key findings

- Successfully entangled ${}^{87} ext{Rb}$ and ${}^{85} ext{Rb}$ atoms.
- Implemented a heteronuclear C--NOT gate with high fidelity.
- Achieved raw fidelities of 0.73 and 0.59 for entanglement and gate operations.

## Abstract

Quantum entanglement is crucial for simulating and understanding exotic physics of strongly correlated many-body systems, such as high--temperature superconductors, or fractional quantum Hall states. The entanglement of non-identical particles exhibits richer physics of strong many-body correlations and offers more opportunities for quantum computation, especially with neutral atoms where in contrast to ions the interparticle interaction is widely tunable by Feshbach resonances. Moreover, the inter-species entanglement forms a basis for the properties of various compound systems, ranging from Bose-Bose mixtures to photosynthetic light-harvesting complexes. So far, the inter-species entanglement has only been obtained for trapped ions. Here we report on the experimental realization of entanglement of two neutral atoms of different isotopes. A ${}^{87}\mathrm{Rb}$ atom and a ${}^{85}\mathrm{Rb}$ atom are confined in two single--atom optical traps separated by 3.8 $\mu$m. Creating a strong Rydberg blockade, we demonstrate a heteronuclear controlled--NOT (C--NOT) quantum gate and generate a heteronuclear entangled state, with raw fidelities $0.73 \pm 0.01$ and $0.59 \pm 0.03$, respectively. Our work, together with the technologies of single--qubit gate and C--NOT gate developed for identical atoms, can be used for simulating any many--body system with multi-species interactions. It also has applications in quantum computing and quantum metrology, since heteronuclear systems exhibit advantages in low crosstalk and in memory protection.