What the MIT group achieved was implementing spin-squeezing to clock operation, but their results are not QPN-limited (in fact, they made it above the SQL, so t

What the MIT group achieved was implementing spin-squeezing to clock operation, but their results are not QPN-limited (in fact, they made it above the SQL, so they actually make things worse instead of making it better) [1]. They attributed their major obstacle as their laser phase noise, and they claimed if they subtract the estimated laser noise from the result they would get sub-SQL. But hey, that's not how things work. If you think you can make it, you just make it. [1] : https://www.nature.com/articles/s41586-020-3006-1 https://www.nature.com/articles/s41586-020-3006-1