Engineering a new generation of atom interferometers

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The huge progress achieved in the manipulation of quantum systems is opening novel routes towards the generation of realistic quantum-based technology. Notably many counterintuitive manifestations of quantum mechanics are turning to be key features for next generation devices, whose performances will beat those of classical machines. Atom interferometry is a hallmark example of that. According to quantum mechanics particles can behave like waves, showing interference as well as light does. In addition, they are very sensitive to the surrounding environment and they have mass, which make of them extremely powerful sensors for measuring linear accelerations and rotations. Implementing reliable atom interferometers for practical applications is however still challenging. State-of-the-art devices are based on atomic samples which are manipulated while they fall due to gravity inside a vacuum apparatus. These interferometers are currently reaching their ultimate performances being limited by technical issues. Their ultimate sensitivity depends in turn on the time available for the interrogation and on the finite atom number. An immediate solution to improve the sensitivity consists in enlarging the interrogation area, at the expenses of the size of the device, and increasing the atom number, at the expenses of the spatial resolution of the atomic probe. To obtain high sensitivity while maintaining the devices compact, a new generation of interferometers based on trapped and guided atoms is emerging. These devices have several advantages: the atoms do not fall and the interrogation time can be long, the use of BECs guarantees micrometrical spatial resolution, and interatomic interactions allow for the preparation of entangled states surpassing the standard quantum limit set by the finite atom number. New challenges also arise: the effects of the confining potentials and interatomic interactions must be controlled at a metrological level. The proposed project aims at realizing novel BEC-based quantum sensors which will be able to surpass the limitations of current trapped and guided interferometers by combining some of the most powerful manipulation techniques currently available in the field of ultracold atoms (and beyond). The two key elements are the accurate tailoring of the optical potentials by a spatial light modulator, and the control of the interactions. This exceptional experimental control will be assisted by theoretical optimization such as short-cut-to-adiabaticity and optimal control techniques. In most atom interferometers to date, the beam splitters are realized by pulsing two laser beams in Bragg or Raman configuration. We will instead engineer innovative splitters directly integrated into the optical waveguides which confine the atoms. They can operate continuously and without the need of extra laser beams. All the elements of the interferometer (beam splitter, phase accumulation and recombiner) will be integrated into the same device by properly sculpturing one single laser beam. First, a complete Mach-Zehnder operation will be performed with a condensate with tunable interactions. A negligible or weakly attractive value of the interactions will be used to suppress interaction-induced decoherence or create dispersionless wavepackets. As a result, high sensitivities are expected for such interferometer. In a second phase of the project, we will demonstrate a Sagnac-like interferometer with non-interacting condensates propagating in a close circuit. This will realize a guided atom gyroscope whose achievement has been a long-standing goal, and which finds an important application in inertial navigation. Finally, we will generate mesoscopic optical tweezers for realizing a dynamical double-well potential for Mach-Zehnder interferometry. By moving the tweezers apart we will control the coupling between the two wells, and by setting strong repulsive interactions we will produce optimally spin-squeezed states.