Article open access publication

Heisenberg-Limited Atom Clocks Based on Entangled Qubits

Physical Review Letters, American Physical Society (APS), ISSN 1079-7114

Volume 112, 19, 2014

DOI:10.1103/physrevlett.112.190403, Dimensions: pub.1031997013, PMID: 24877919,


Kessler, E M (1) (2)
Bishof, M (3)
Jiang, L (4)
Ye, J (3)



  1. (1) Harvard-Smithsonian Center for Astrophysics, grid.455754.2
  2. (2) Harvard University, grid.38142.3c
  3. (3) University of Colorado System, grid.266185.e
  4. (4) Yale University, grid.47100.32
  5. (5) University of Copenhagen, grid.5254.6, KU


We present a quantum-enhanced atomic clock protocol based on groups of sequentially larger Greenberger-Horne-Zeilinger (GHZ) states that achieves the best clock stability allowed by quantum theory up to a logarithmic correction. Importantly the protocol is designed to work under realistic conditions where the drift of the phase of the laser interrogating the atoms is the main source of decoherence. The simultaneous interrogation of the laser phase with a cascade of GHZ states realizes an incoherent version of the phase estimation algorithm that enables Heisenberg-limited operation while extending the coherent interrogation time beyond the laser noise limit. We compare and merge the new protocol with existing state of the art interrogation schemes, and identify the precise conditions under which entanglement provides an advantage for clock stabilization: it allows a significant gain in the stability for short averaging time.


Funders and Grants

Research Categories

Main Subject Area

Fields of Research

Links & Metrics

NORA University Profiles

University of Copenhagen

Dimensions Citation Indicators

Times Cited: 56

Field Citation Ratio (FCR): 18

Relative Citation ratio (RCR): 1.05

Open Access Info

Green, Submitted