Macroscopic maximally entangled state preparation between two atomic ensembles

TL;DR

This paper presents a protocol to deterministically generate a macroscopic maximally entangled state between two atomic ensembles using adaptive QND measurements, without postselection, and beyond the Holstein-Primakoff approximation.

Contribution

The authors develop a novel adaptive measurement scheme that produces genuine macroscopic entanglement between atomic ensembles without postselection and applicable beyond the Holstein-Primakoff regime.

Findings

Achieves deterministic preparation of maximally entangled states.

Works beyond the Holstein-Primakoff approximation.

Produces genuine macroscopic entanglement.

Abstract

We develop a scheme to prepare a macroscopic maximally entangled state (MMES) 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 basis 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.