Bell States of Atoms with Ultralong Lifetimes and Their Tomographic State Analysis

TLDR

The study investigates the temporal decay of entanglement in Bell states. The authors deterministically generate arbitrary Bell states of two trapped ions, quantify entanglement, reconstruct the density matrix via single‑qubit rotations and high‑efficiency measurements, and present the method as a foundation for future quantum process tomography. The Bell states exhibit ultralong lifetimes approaching the spontaneous emission limit, exceeding all previously reported values by three orders of magnitude.

Abstract

Arbitrary atomic Bell states with two trapped ions are generated in a deterministic and preprogrammed way. The resulting entanglement is quantitatively analyzed using various measures of entanglement. For this, we reconstruct the density matrix using single qubit rotations and subsequent measurements with near-unity detection efficiency. This procedure represents the basic building block for future process tomography of quantum computations. As a first application, the temporal decay of entanglement is investigated in detail. We observe ultralong lifetimes for the Bell states Psi(+/-), close to the fundamental limit set by the spontaneous emission from the metastable upper qubit level and longer than all reported values by 3 orders of magnitude.