Research

In our experiment, we manipulate macroscopic systems and make them behave according to the laws of quantum physics. We want to explore the terra incognita of quantum mechanics at large masses and length scales.

Levitation of Solids

A levitated solid object is at the heart of our experiments. In our laboratory, we routinely perform levitation by using either lasers or oscillating radio-frequency electric fields. The objects we levitate are typically nonometer-sized and contains billions of atoms, often in a disordered arrangemenet.

Despite the internal complexity, all these atoms contribute to a collective center-of-mass motion that is frictionless when we place the object in vacuum. This platform is the perfect playground to study the laws of quantum physics on a macroscopic object.

We realize in practice a Heisenberg microscope with which we monitor not a single elementary particle but rather a nanosphere of billions of atoms: we observe how the nanoparticle is disturbed by our action of measuring its position.

Using such a precise microscope, we can follow and control the motion of the suspended nanoparticle in real time. Following this principle, we can prepare states that are close to the lowest energy level allowed by quantum mechanics (ground state), or that have an uncertainty in position or momentum that is reduced below its zero-point value (squeezed state).

We can also reveal the quantum correlations imprinted on the scattered laser beam by the moving object: these correlations underlie one of the most important aspects of quantum physics: the entanglement between the nanoparticle and the scattered photons.

In the future, we want to explore even furhter the wealth of quantum phenomena with a levitated nanoparticle: can we “blur”, delocalize the nanoparticle as much as its diameter? Is it possible to put the nanoparticle in a Schrödinger’s cat state, with the two heads separated by a macroscopic distance? What is the gravitational force generated by such a quantum source mass?

Measurements at the Quantum Limits

Low-dissipation mechanical resonators oscillate for long time when perturbed by an external force. This is advantageous for sensing, because we can monitor these oscillations with increasing precision to infer the force strength. Force sensors based on this principle are ubiquitous in science and technology: from microelelectromechanical systems (MEMS) in smartphones to the kilogram-scale pendulums in gravitational wave observatories. However, quantum physics predicts that as we increase the precision of our measurements, we inevitably introduce a disturbance, known as quantum backaction.

We study the trade-off between imprecision and quantum backaction using an engineered nanomechanical membrane resonator, interrogated by a laser beam. We can clearly distinguish the phenomenon of quantum backaction. In addition, we can take advantage of quantum states of light to break this trade-off and improve our sensitivity.