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Entanglement and spin squeezing in a network of distant optical lattice clocks

Eugene S. Polzik and Jun Ye
Phys. Rev. A 93, 021404(R) – Published 17 February 2016

Abstract

We propose an approach for the collective enhancement of precision for remote optical lattice clocks and a way of generating the Einstein-Podolsky-Rosen (EPR) state of remote clocks. In the first scenario, a distributed spin-squeezed state (SSS) of M clocks is generated by a collective optical quantum nondemolition measurement on clocks with parallel Bloch vectors. Surprisingly, optical losses, which usually present the main limitation to SSS, can be overcome by an optimal network design which provides close to Heisenberg scaling of the time precision with the number of clocks M. We provide an optimal network solution for distant clocks as well as for clocks positioned within close proximity of each other. In the second scenario, we employ collective dissipation to drive two clocks with oppositely oriented Bloch vectors into a steady-state entanglement. The corresponding EPR state provides secret time sharing beyond the projection noise limit between the two quantum synchronized clocks protected from eavesdropping. An important application of the EPR-entangled clock pair is the remote sensing of, for example, gravitational effects and other disturbances to which clock synchronization is sensitive.

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  • Received 11 August 2015
  • Revised 28 November 2015

DOI:https://doi.org/10.1103/PhysRevA.93.021404

©2016 American Physical Society

Physics Subject Headings (PhySH)

Atomic, Molecular & Optical

Authors & Affiliations

Eugene S. Polzik1 and Jun Ye2

  • 1Niels Bohr Institute, University of Copenhagen, Blegdamsvej 17, 2100 Copenhagen, Denmark
  • 2JILA, National Institute of Standards and Technology and University of Colorado, Boulder, Colorado 80309-0440, USA

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Issue

Vol. 93, Iss. 2 — February 2016

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