The stability of several clock protocols based on 2 to 20 entangled atoms is evaluated numerically, by a simulation that includes the effect of decoherence due to classical oscillator noise. In this context the squeezed states proposed by Andre, Sorensen, and Lukin [PRL 92, 239801 (2004)] offer reduced instability compared to clocks based on Ramsey's protocol with unentangled atoms. When more than fifteen atoms are simulated, the protocol suggested by Buzek,Derka and Massar [PRL 82, 2207 (1999)] has lower instability. A large-scale numerical search for optimal clock protocols with 2 to 8 qubits yields improved clock stability compared to Ramsey spectroscopy, but no performance gains with respect to the other protocols. In the simulations, a laser local oscillator decoheres due to flicker-frequency (1/f) noise. The oscillator frequency is repeatedly corrected, based on projective measurements of the qubits, which are assumed not to decohere with one another.
Proceedings of the 20th International Conference on Laser Spectroscopy
May 30-June 3, 2011
The 20th International Conference on Laser Spectroscopy ICOLS 2011