Team

Project leader	Philippe Courteille
Post-docs	Dalila Rivero and Ana Cipris
PhD student	Gustavo Henrique de França
Master student	Claudio Alves Pessoa Junior

Talk BuenosAires

Motive

A quantum sensor is a measuring device that takes advantage of quantum correlations, such as states in a quantum superposition or entanglement, for better sensitivity and resolution than can be obtained by classical systems. Unlike what happens in the classical case, the quantum sensor changes its state and uncertainty in the measurement process.

An example of a quantum sensor is the atomic gravimeter, which is based on atomic wave interference. A particularly appealing interferometric technique, translating the gravitational acceleration force into a frequency measurement, detects the Bloch oscillations of laser-cooled atoms confined in a vertical standing light wave. In modern gravimeters the oscillations are mapped by measuring the state of the atoms after variable evolution times. The measurement is destructive, and new atomic samples have to be prepared for every chosen evolution time. In contrast, cold atoms can be made to perform more than 10000 Bloch oscillations in a single run, so that their nondestructive monitoring would be highly beneficial. To overcome the destructive nature of the measurements in atomic gravimeters, we propose in this project a novel technique monitoring the Bloch oscillations in-vivo by letting the atoms interact with a ring cavity. In certain parameter regimes, the backaction of the atomic oscillatory motion onto the phase and amplitude of the intracavity leads to detectable light bursts, which may serve as a reliable monitor, as we have shown by numerical simulations published in [Marina04] and [Marina05].

Gravimeter experiment at São Carlos

At the Instituto de Física de São Carlos we ideally combine technical know-how in the construction and operation of high-finesse ring cavities and in the trapping and cooling of strontium. Therefore, we started the construction of new experiment aiming at testing the viability of ring cavities to monitor gravity-induced Bloch oscillations.

Since July 2018 we are able to trap 3 millions strontium atoms at a few mK temperature in a blue MOT. The atomic cloud is located inside the mode volume of a 3.4cm long optical ring cavity with finesse on the order of 1000. Our current efforts aim, on one hand, at cooling the atoms further down to 1µK via a red MOT, as demonstrated in our other lab. On the other hand, we are keen to see signatures of the presence of atoms in the ring cavity, either via normal-mode splitting, as done in [Culver15] or via CARL.

Metrology

Strontium exhibits ultranarrow intercombination transitions with mHz linewidths. For this reason, they are among the hottest candidates for optical frequency standards. By means of a frequency comb recently acquired by our lab, we plan to link the optical frequency regime to the microwave regime, where we can compare to our cesium atomic fountain clock [Martin Júnior18].

Spectroscopy on ultranarrow transitions requires extremely stable lasers. We have set up and tested a laser spectrometer for controlling the eigenfrequencies of our ring cavity with kHz precision. The results will be published soon [Dalila21]

Page updated on July 2021