Reduced spin measurement back-action for a phase sensitivity ten times beyond the standard quantum limit

By J. Bohnet, K. Cox, M. Norcia, J. Weiner, Zilong Chen, James K. Thompson. Nature Photonics, 2013

155 citations recorded by the source corpus.

Fundamental quantum noise limits the precision of quantum-based detectors, for example limiting the ultimate precision of atomic clocks, which have applications in communication, navigation and tests of fundamental physics. Collective measurements of many quantum spins can project the ensemble into an entangled, spin-squeezed state with improved quantum-limited measurement resolution. However, measurement back-action has limited previous implementations of collective measurements to only modest observed enhancements in precision. Here, we experimentally demonstrate a collective measurement with reduced measurement back-action to produce and directly observe, with no background subtraction, a spin-squeezed state with phase resolution improved by a factor of 10.5(1.5) in variance, or 10.2(6) dB, compared to the initially unentangled ensemble of N = 4.8 × 105 87Rb atoms. The measurement uses a cavity-enhanced probe of an optical cycling transition, mitigating back-action associated with state-changing transitions induced by the probe. This work establishes collective measurements as a powerful technique for generating useful entanglement for precision measurements. The phase of a collection of spins is measured with a sensitivity ten times beyond the limit set by the quantum noise of an unentangled ensemble of 87Rb atoms. A cavity-enhanced probe of an optical cycling transition is employed to mitigate back-action associated with state-changing transitions induced by the probe.

Subfields: Artificial Intelligence, Atomic and Molecular Physics, and Optics

View Paper: https://www.semanticscholar.org/paper/387253caa53ea2ff3d2787fdcd836fac58be1222

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Citations in the corpus

Entanglement certification from theory to experiment (2018, methodology): “[323] J.”
Quantum metrology with nonclassical states of atomic ensembles (2016, background): “In the experiments of Bohnet et al. (2014); Chen et al. (2011); and Cox et al. (2016), the atom number Nb is measured non-destructively by probing the cavity resonant frequency with an additional probe laser injected into the cavity.”