Co-levitated nanoparticles can exhibit strong and tunable interactions through light scattering. Importantly, this optical binding interaction can be non-reciprocal, i.e. it seemingly violates Newton's law of action equals reaction. We study the quantum dynamics of non-reciprocally interacting levitated nanoparticle arrays and investigate how their dynamics can be exploited for force and torque sensing.

The non-linearity of free rigid body rotations gives rise to pronounced quantum interference effects, with no analogues in the body’s free centre-of-mass motion. Optically or electrically trapping and manipulating aspherical nanoparticles thus provides an attractive platform for tests of quantum physics and for sensing at the quantum limit. We work on techniques to control and observe the mechanical rotation of nanoscale dielectrics, and develop strategies to for macroscopic tests of quantum mechanics.

Levitated nanoparticles can exhibit exceptionally strong spin-rotational coupling due to the Einstein-de Haas/Barnett effects. We investigate the impact of embedded paramagnetic impurities on the quantum rotation dynamics of the host particle. For instance, controlling the quantum state of internal spin degrees of freedom allows preparing and reading-out rotational quantum interference of particles.

A nanoscale object interacting with an uncontrolled environment gradually loses its coherence and classicalizes. Quantitatively understanding this process is crucial for future quantum tests and sensing applications of complex quantum systems. We develop decoherence models for the mechanical motion of macromolecules and nanoscale particles and apply them to realistic experimental setups.  

The interference pattern of large molecules crucially depends on how the particles interact with diffraction gratings. This provides an attractive way to access otherwise elusive molecular properties, such as their optical polarizabilities or absorption cross sections. On the other hand, their interaction with the grating can be used to control the mechanical quantum state of the molecules. We study how diffraction experiments can be used for molecular metrology and to manipulate molecular beams in unprecedented ways.