There's a different article on the same topic which isn't paywalled at https://physics.aps.org/articles/v17/161 https://physics.aps.org/articles/v17/161 . It a

There's a different article on the same topic which isn't paywalled at https://physics.aps.org/articles/v17/161 https://physics.aps.org/articles/v17/161 . It also provides links at the bottom to the papers being discussed.