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Deterministic entanglement generation from driving through quantum phase transitions

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Science  10 Feb 2017:
Vol. 355, Issue 6325, pp. 620-623
DOI: 10.1126/science.aag1106

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Transitional approach to entanglement

In an entangled many-particle system, changing the state of one constituent affects the rest of the system. This property can be used as a resource in quantum information processing, but getting many particles to participate in entanglement is tricky. Luo et al. used another collective phenomenon, a quantum phase transition, to entangle more than 900 atoms in a Bose-Einstein condensate. The size of the entangled ensemble remained stable, making the approach practical for precision measurements.

Science, this issue p. 620

Abstract

Many-body entanglement is often created through the system evolution, aided by nonlinear interactions between the constituting particles. These very dynamics, however, can also lead to fluctuations and degradation of the entanglement if the interactions cannot be controlled. Here, we demonstrate near-deterministic generation of an entangled twin-Fock condensate of ~11,000 atoms by driving a rubidium-87 Bose-Einstein condensate undergoing spin mixing through two consecutive quantum phase transitions (QPTs). We directly observe number squeezing of 10.7 ± 0.6 decibels and normalized collective spin length of 0.99 ± 0.01. Together, these observations allow us to infer an entanglement-enhanced phase sensitivity of ~6 decibels beyond the standard quantum limit and an entanglement breadth of ~910 atoms. Our work highlights the power of generating large-scale useful entanglement by taking advantage of the different entanglement landscapes separated by QPTs.

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