Collective manipulation of quantum entangled states

Anthony Chefles, Claire R Gilson, Stephen M Barnett

Zhuan Li

Based on the three-Λ dark-state polaritons,quantum information can be exchanged not only between the three-signal fields and the collective atoms,but also among the three signal fields.Some three-mode quantum states can be stored in the three-Λ atomic ensemble,thus the quantum information of the three-signal field can be written and read in the medium.Furthermore,with this scheme some tripartite entangled states can be generated,stored,retrieved,transformed and so on,thus the ability of the manipulation of entangled states is improved.

Dik Bouwmeester

Felix Knollmann, Sabrina Corsetti, Ethan Clements +12 more

Spontaneously emitted photons are entangled with the electronic and nuclear degrees of freedom of the emitting atom, so interference and measurement of these photons can entangle separate matter-based quantum systems as a resource for quantum information processing. Since confinement in a single-mode facilitates the photon interference needed for generating entanglement, the dipole emission patterns relevant in spontaneous emission present a mode-matching challenge. Current demonstrations rely on bulk photon-collection and manipulation optics that suffer from large component size and system-to-system variability-factors that impede scaling to the large numbers of entangled pairs needed for quantum information processing. To address these limitations, we demonstrate a collection method that enables passive phase stability, straightforward photonic manipulation, and intrinsic reproducibility. Specifically, we engineer a waveguide-integrated grating to couple photons emitted from a trapped ion into a single optical mode within a microfabricated ion-trap chip. Using the integrated collection optic, we characterize the collection efficiency, image the ion, and detect the ion's quantum state. The integrated optic covers 2.18% of the solid angle and collects 1.97 ± 0.3% of the spontaneously emitted light incident on the grating for a total collection efficiency of 0.043% into a single-mode waveguide. This proof-of-principle demonstration lays the foundation for leveraging the inherent stability and reproducibility of integrated photonics to create, manipulate, and measure multipartite quantum states in arrays of quantum emitters.

J. I. Cirac, P. Zoller

One of the most intriguing features of quantum mechanics is the existence of entangled states. These states result from the superposition of individual quantum states in composite systems, such as a collection of particles, and cannot be expressed as a product of the individual states. The generation and manipulation of entangled states is fundamental to studies of the most basic aspects of quantum mechanics, and provides the basis of applications such as quantum computing, quantum communications and high-precision spectroscopy.

Jānis Ruža