N-atom collective-state atomic clock with N -fold increase in effective frequency and N -fold reduction in fringe width

May E. Kim, Resham Sarkar, Renpeng Fang, Selim M. Shahriar

Research output: Contribution to journalArticlepeer-review

6 Scopus citations


We describe a collective state atomic clock (COSAC) with Ramsey fringes narrowed by a factor of N compared to a conventional clock - N being the number of noninteracting atoms - without violating the uncertainty relation. This narrowing is explained as being due to interferences among the collective states, representing an effective N-fold increase in the clock frequency, without entanglement. We discuss the experimental inhomogeneities that affect the signal and show that experimental parameters can be adjusted to produce a near ideal signal. The detection process collects fluorescence through stimulated Raman scattering of Stokes photons, which emits photons predominantly in the direction of the probe beam for a high enough optical density. By using a null measurement scheme, in which detection of zero photons corresponds to the system being in a single collective state, we detect the population in a collective state of interest. The quantum and classical noise of the ideal COSAC is still limited by the standard quantum limit and performs only as well as the conventional clock. However, when detection efficiency and collection efficiency are taken into account, the detection scheme of the COSAC increases the quantum efficiency of detection significantly in comparison to a typical conventional clock employing fluorescence detection, yielding a net improvement in stability by as much as a factor of 10.

Original languageEnglish (US)
Article number063629
JournalPhysical Review A - Atomic, Molecular, and Optical Physics
Issue number6
StatePublished - Jun 24 2015

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics


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