Quantum spin dynamics and entanglement generation with hundreds of trapped ions

TL;DR

This paper demonstrates the generation and verification of entanglement in a large 2D array of trapped ions, advancing quantum simulation capabilities for complex spin models with over 200 ions.

Contribution

It reports the first observation of entanglement in a 2D ion array with over 200 ions, using engineered Ising interactions and verifying non-Gaussian states, expanding quantum simulation scale.

Findings

Verified spin-squeezed states with 4.0±0.9 dB enhancement in 219 ions

Observed non-Gaussian, over-squeezed states in full counting statistics

Good agreement with ab-initio theory including decoherence effects

Abstract

Quantum simulation of spin models can provide insight into complex problems that are difficult or impossible to study with classical computers. Trapped ions are an established platform for quantum simulation, but only systems with fewer than 20 ions have demonstrated quantum correlations. Here we study non-equilibrium, quantum spin dynamics arising from an engineered, homogeneous Ising interaction in a two-dimensional array of $^9$Be$^+$ ions in a Penning trap. We verify entanglement in the form of spin-squeezed states for up to 219 ions, directly observing 4.0$\pm$0.9 dB of spectroscopic enhancement. We also observe evidence of non-Gaussian, over-squeezed states in the full counting statistics. We find good agreement with ab-initio theory that includes competition between entanglement and decoherence, laying the groundwork for simulations of the transverse-field Ising model with variable-range interactions, for which numerical solutions are, in general, classically intractable.