Macroscopic quantum physics

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 attracitive platform for tests of quantum physics and for sensing at the quantum limit. Together with our experimental collaborators, we work on techniques to control and observe the mechanical rotation of nanoscale dielectrics, and develop schemes to witness orientational quantum revivals and the quantum version of the tennis-racket effect.


Quantum spin rotors

Levitated nanoparticles can exhibit exceptionally strong spin-rotational coupling due to the Einstein-de Haas/Barnett effects. In an ongoing project, we investigate the impact of embedded paramagnetic impurities on the quantum rotation dynamics of levitated nanodiamonds together with the experimental team of Gabriel Hétet. Controlling the quantum state of internal spin degrees of freedom may allow preparing and reading-out rotational quantum interference of particles containing billions of atoms.

Levitated quantum electromechanics

Electric traps are ideally suited for stably levitating nano- to microscale dielectrics in ultrahigh vacuum, providing an attractive platform for sensing and tests of for fundamental physics. Levitated nanoparticles can be connected to an electrical circuit via the endcap electrodes, through which its motion can be cooled, monitored, and manipulated. In a recent work we demonstrated how superconducting qubits can be used to generate and readout quantum superpositions of the motional quantum state of a highly charged dielectric.

Orientational decoherence of quantum rigid rotors

A nanoscale rigid rotor revolving in a homogeneous background gas experiences random collisions with the surrounding gas atoms. These collisions lead to a gradual loss of orientational coherence, and thus classicalize the quantum state of the rotor. In several recent works, we developed the theory of environmental decoherence, friction, and thermalization of arbitrarily shaped quantum rigid rotors. Application of the derived equations to a recent experiment with nitrogen superrotors yields excellent agreement.

Molecular matter-wave interference

The interference pattern of large molecules crucially depends on how the particles interact with the diffraction grating. 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 quantum state of the molecules. In recent works we demonstrated Bragg diffraction of large molecules, showed how a combination of molecular diffraction and spatial filtering serves to separate different conformers, and investigated the role of molecular rotations in molecule interference.