Matter-Wave Gravimeter Incorporated into an Atom Chip

A method of measuring the gravitational field or an acceleration in a given direction of measurement by means of a gravimeter, of the matter-wave type, said gravimeter comprising at least:

• an electronic chip comprising a measuring plane;
• means for generating, capturing and cooling an ultracold atom cloud and an atom trap making it possible to immobilize the ultracold atom cloud;
• the trap comprising on the one hand a first main conductor wire incorporated into said chip and, on the other hand, external means for generating a magnetic field resulting in a local magnetic field minimum in the vicinity of the chip;
• means for splitting the atom cloud into two packets of atoms, said splitting means essentially comprising a second conductor wire and a third conductor wire substantially parallel in the zone of the trap to the main conductor wire and placed symmetrically on either side of this first wire, the second wire being traversed by a first alternating current, the third wire being traversed by a second alternating current of the same amplitude, of the same frequency as the first alternating current and in the opposite direction, the amplitudes of the first and of the second current being able to vary simultaneously,
• optical means for measuring the phase shift introduced on the atom cloud after recombination;
• electronic means for controlling, commanding and slaving of the various means of the gravimeter;
• wherein the taking of a measurement comprises the following phases:
• Phase 1, called the generation phase:
• Generation, cooling and trapping of an ultracold atom cloud at a predetermined height in the vicinity of said measuring plane;
• Phase 2, called the splitting phase:
• Progressive and simultaneous increasing of the first and second alternating currents until the amplitude and the frequency of said currents are sufficient to create at the atom cloud a magnetic splitting field with an intensity greater than the magnetic intensity necessary to split the atom cloud into two atom packets, the two packets being separated by a determined distance in a direction parallel to the direction of measurement;
• Phase 3, called the interrogation phase:
• Maintenance of the amplitudes of the alternating currents so as to preserve the split for a predetermined period of time;
• Phase 4, called the recombination phase:
• Reduction of the amplitudes of the alternating currents so as to recombine the two atom packets into a single phase-shifted atom cloud;
• Phase 5, called the measurement phase:
• Measurement of the phase shift by the optical measuring means.