15 July 2014 Editors’ choice in APL and Science

Artistic impression of the experiment

Highlighted results on ultra-sensitive magnetometers and non-linear interferometers Two studies published by the Quantum information with cold atoms and non-classical light research group, led by ICREA Prof at ICFO Morgan Mitchell, have been selected by two different journals to appear in the editors’ choice corner. While the article entitled “Real-time vector field tracking with a cold-atom magnetometer” was selected by the editors of Applied Physics Letters, the article entitled “Ultrasensitive Atomic Spin Measurements with a Nonlinear Interferometer” was highlighted by Science.

In the first study, researchers Behbood et al. were able to demonstrate a fast three-axis magnetometer using cold, optically trapped Rubidium gas as a sensor. By means of near-resonant Faraday rotation, they were able to record the free-induction decay of a spin polarized ensemble, measuring the three field components and one gradient component, while achieving sub-nT sensitivities, 20m transverse spatial resolution and 1ms temporal resolution. The setup used was shown to be a very attractive device for non-disturbing field monitoring and control.

In the second study, researchers Sewell et al. were able to experimentally demonstrate that interferometers, the most sensitive measuring instruments yet invented, can be improved using nonlinear physics. Without generating entanglement among the photons, researchers were able to enhance the signal of the interferometer because the response of one photon is simultaneously improved by the presence of other photons within the device. In their experiment, they were able to demonstrate that a nonlinear interferometer outperforms its linear counterparts when a sufficiently large number of photons is used in the measurement.