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The question is whether entanglement can improve the very best clocks in absolute terms.","posed_since":"","precise":"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.","problem_ref":"52a23990da843f76fe38fd54b43c81d48e502434a70bfa1ce70488fa90121e47","references":"","settled_by":"A clock comparison showing an entanglement-enabled absolute stability improvement over the unentangled state of the art.","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.","title":"Can entanglement improve a clock already at the stability 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