Revision 2

Accepted · core change · record

Changes against revision 1:

Title: Can entanglement improve a clock already at the stability frontier?
Plain: Squeezed atom states (correlated states with reduced noise in one quantity) have beaten the standard limit in clocks, but only in setups that were not the most stable clocks available. The question is whether entanglement can improve the very best clocks in absolute terms.
Precise · changed · core: Revision 1: Demonstrate an optical lattice or tweezer clock whose absolute fractional frequency instability, with entangled or squeezed atomic states, is below that of the best unentangled clock with the same atom number and interrogation hardware, at instability levels of order 1e-17 at 1 s or better.; Revision 2: Demonstrate an optical lattice or tweezer clock whose absolute fractional frequency instability, with entangled or squeezed atomic states, is below that of the best unentangled clock with the same atom number and interrogation hardware, at instability levels of order $10^{-17}$ at 1 s or better.
Settled by: A clock comparison showing an entanglement-enabled absolute stability improvement over the unentangled state of the art.
Kind: well-posed
Answer type: yes-no
References: (empty)
Literature status: open
Status note: Spin squeezing in optical clocks gave gains of a few dB below the standard quantum limit in differential comparisons (2023-2024), not an absolute record.
Posed since: (empty)

Decisions