Entanglement on an optical atomic-clock transition.

@article{PedrozoPeafiel2020EntanglementOA,
  title={Entanglement on an optical atomic-clock transition.},
  author={Edwin Pedrozo-Pe{\~n}afiel and Simone Colombo and Chi Shu and Albert F. Adiyatullin and Zeyang Li and Enrique Mendez and Boris Braverman and Akio Kawasaki and Daisuke Akamatsu and Yanhong Xiao and Vladan Vuleti{\'c}},
  journal={Nature},
  year={2020},
  volume={588 7838},
  pages={
          414-418
        }
}
State-of-the-art atomic clocks are based on the precise detection of the energy difference between two atomic levels, which is measured in terms of the quantum phase accumulated over a given time interval1-4. The stability of optical-lattice clocks (OLCs) is limited both by the interrupted interrogation of the atomic system by the local-oscillator laser (Dick noise5) and by the standard quantum limit (SQL) that arises from the quantum noise associated with discrete measurement outcomes… 
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References

SHOWING 1-10 OF 47 REFERENCES
Ultrastable optical clock with two cold-atom ensembles
Optical clocks with a record low zero-dead-time instability of 6 × 10–17 at 1 second are demonstrated in two cold-ytterbium systems. The two systems are interrogated by a shared optical local
Atom-chip-based generation of entanglement for quantum metrology
TLDR
The experimental generation of multi-particle entanglement on an atom chip is reported by controlling elastic collisional interactions with a state-dependent potential to generate spin-squeezed states of a two-component Bose–Einstein condensate; such states are a useful resource for quantum metrology.
Quantum metrology with nonclassical states of atomic ensembles
Quantum technologies exploit entanglement to revolutionize computing, measurements, and communications. This has stimulated the research in different areas of physics to engineer and manipulate
Mesoscopic atomic entanglement for precision measurements beyond the standard quantum limit
TLDR
There is an optimal degree of decoherence induced by the quantum measurement which maximizes the generated entanglement, and a 2-color QND scheme used in this paper is shown to have a number of advantages for entanglements generation as compared with a single- color QND measurement.
Comparison of two independent Sr optical clocks with 1×10(-17) stability at 10(3) s.
TLDR
This work synchronously probing two ^{87}Sr lattice systems using a laser with a thermal noise floor of 1×10(-15), removes classically correlated laser noise from the intercomparison, and demonstrates an order of magnitude improvement over the best reported stability of any independent clock.
New bounds on dark matter coupling from a global network of optical atomic clocks
TLDR
A two orders of magnitude improvement in constraints on transient variations of the fine-structure constant is reported, which considerably improves the detection limit for the standard model (SM)–DM coupling.
Demonstration of 4.8 × 10−17 stability at 1 s for two independent optical clocks
Optical atomic clocks require local oscillators with exceptional optical coherence owing to the challenge of performing spectroscopy on their ultranarrow-linewidth clock transitions. Advances in
A noise-immune cavity-assisted non-destructive detection for an optical lattice clock in the quantum regime
We present and implement a non-destructive detection scheme for the transition probability readout of an optical lattice clock. The scheme relies on a differential heterodyne measurement of the
Near-Unitary Spin Squeezing in ^{171}Yb.
TLDR
Substantial and nearly unitary spin squeezing is reported in ^{171}Yb, an optical lattice clock atom, and an interferometer is demonstrated that improves the averaging time over the SQL by a factor of 3.7(2).
Seconds-scale coherence on an optical clock transition in a tweezer array
TLDR
A platform that combines the key strengths of these two approaches, based on arrays of individual strontium atoms held within optical tweezers is demonstrated, establishing optical tweezer arrays as a powerful tool for coherent control of optical transitions for metrology and quantum information science.
...
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