Macroscopic maximally-entangled-state preparation between two atomic ensembles
Manish Chaudhary, Ebubechukwu O. Ilo-Okeke, Valentin Ivannikov, Tim Byrnes · Physical Review A · 2023
We develop a scheme to prepare a macroscopic maximally entangled state between two atomic ensembles using adaptive quantum nondemolition (QND) measurements. The quantum state of the system is evolved using a sequence of QND measurements followed by adaptive unitaries such that the desired measurement outcome is obtained with asymptotically unit probability. This procedure is repeated in $z$- and $x$-spin bases alternately such that the state converges deterministically towards the maximally entangled state. Up to a local spin-basis rotation, the maximally entangled state has zero total spin angular momentum, i.e., it is a singlet state. Our protocol does not perform postselection and works beyond the Holstein-Primakoff regime for the atomic spin degrees of freedom, producing genuine macroscopic entanglement.