181 research outputs found
Heisenberg-Limited Atom Clocks Based on Entangled Qubits
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.Physic
Suppression of collisional shifts in a strongly interacting lattice clock
Optical lattice clocks have the potential for extremely high frequency
stability owing to the simultaneous interrogation of many atoms, but this
precision may come at the cost of systematic inaccuracy due to atomic
interactions. Density-dependent frequency shifts can occur even in a clock that
uses fermionic atoms if they are subject to inhomogeneous optical excitation
[1, 2]. Here we present a seemingly paradoxical solution to this problem. By
dramatically increasing the strength of atomic interactions, we suppress
collisional shifts in lattice sites containing > 1 atoms; strong
interactions introduce an energy splitting into the system, and evolution into
a many-particle state in which collisions occur is inhibited. We demonstrate
the effectiveness of this approach with the JILA Sr lattice clock by reducing
both the collisional frequency shift and its uncertainty by more than a factor
of ten [3], to the level of . This result eliminates the compromise
between precision and accuracy in a many-particle system, since both will
continue to improve as the particle number increases.Comment: 13 pages, 6 figure
Resolved atomic interaction sidebands in an optical clock transition
We report the observation of resolved atomic interaction sidebands (ISB) in
the Sr optical clock transition when atoms at microkelvin temperatures
are confined in a two-dimensional (2D) optical lattice. The ISB are a
manifestation of the strong interactions that occur between atoms confined in a
quasi-one-dimensional geometry and disappear when the confinement is relaxed
along one dimension. The emergence of ISB is linked to the recently observed
suppression of collisional frequency shifts in [1]. At the current
temperatures, the ISB can be resolved but are broad. At lower temperatures, ISB
are predicted to be substantially narrower and usable as powerful spectroscopic
tools in strongly interacting alkaline-earth gases
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