2013/12/17 by Shlomi Kotler, Nitzan Akerman, Nir Navon +2 · 1 citation
Computer Science · Physics and Astronomy · #Atomic and Subatomic Physics Research #Atomic physics #Electron #Ion #Nuclear physics #Physics #Quantum Information and Cryptography #Quantum mechanics #Quantum optics and atomic interactions #quant-ph
paper · pdf · doi:10.1038/nature13403
published as Nature 510, 376 (2014) · 4 figures
arxiv created 2013/12/17 · openalex publication_date 2014/06/01 · arxiv updated 2015/02/02 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
Electrons have an intrinsic, indivisible, magnetic dipole aligned with their internal angular momentum (spin). The magnetic interaction between two electrons can therefore impose a change in their spin orientation. This process, however, was never observed in experiment. The challenge is two-fold. At the atomic scale, where the coupling is relatively large, the magnetic interaction is often overshadowed by the much larger coulomb exchange counterpart. In typical situations where exchange is negligible, magnetic interactions are also very weak and well below ambient magnetic noise. Here we report on the first measurement of the magnetic interaction between two electronic spins. To this end, we used the ground state valence electrons of two 88Sr+ ions, co-trapped in an electric Paul trap and separated by more than two micrometers. We measured the weak, millihertz scale (alternatively 10-18 eV or 10-14 K), magnetic interaction between their electronic spins. This, in the presence of magnetic noise that was six orders of magnitude larger than the respective magnetic fields the electrons apply on each other. Cooperative spin dynamics was kept coherent for 15 s during which spin-entanglement was generated. The sensitivity necessary for this measurement was provided by restricting the spin evolution to a Decoherence-Free Subspace (DFS) which is immune to collective magnetic field noise. Finally, by varying the separation between the two ions, we were able to recover the inverse cubic distance dependence of the interaction. The reported method suggests an alternative route to the search of long-range anomalous spin-spin forces and can be generalized to include Quantum Error Correction codes for other cases of extremely weak signal detection.