A clock of atoms is spin-squeezed to a Wineland parameter .

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Quantum Information and Technology, Ch Quantum metrology and sensing

Problem

A clock of N=105N=10^5 atoms is spin-squeezed to a Wineland parameter ξ2=0.05\xi^2=0.05. ((a)) Find the one-shot phase uncertainty Δφ=ξ/N\Delta\varphi=\xi/\sqrt N. ((b)) Find the factor by which this beats the standard quantum limit, 1/N1/\sqrt N. ((c)) Find the factor by which it still falls short of the Heisenberg limit, 1/N1/N. ((d)) State whether the atoms are certified entangled by this value of ξ2\xi^2, and why. ((e)) Find the ξ2\xi^2 (and the equivalent figure in decibels, −10log⁡10ξ2-10\log_{10}\xi^2) that would be needed for a tenfold gain over the standard quantum limit.

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