AMO Seminar: Lorenzo Magrini, University of Vienna, “Quantum measurement and control of mechanical motion at room temperature”

The Heisenberg uncertainty principle establishes the frontier to the quantum realm. The position of a particle, the spin of an atom, the energy of a photon can only be known with finite precision. Realizing measurements close to this limit requires high detection efficiency and good environmental isolation. These are challenging tasks, especially with macroscopic systems and at room temperature. In this talk, I will describe how the motion of a levitated glass sphere (150 nm diameter) at room temperature can be measured and controlled at this quantum limit. First I will discuss a measurement scheme that relies on near field coupling of the particle to a photonic crystal cavity, demonstrating an exciting interface for the study of optical fields in super-resolution and short-range forces. In the second part, I will introduce a truly quantum-limited measurement. This is achieved by confocal microscopy, which, together with optimal control theory allows us to track the quantum trajectory of the particle in real-time and to use feedback to reduce its energy to the quantum ground state. In the last part of the seminar, I will show how this efficient quantum measurement is also used to observe light squeezing by radiation pressure forces on the oscillating particle even without an optical resonator. Achieving this level of quantum control by measurement and feedback on a levitated system that is made of billions of atoms and at room temperature represents an important step for the development of extraordinary force and impulse sensors and will perhaps help future experiments addressing some of the most intriguing open questions in fundamental physics.
Please email Daphne Klemme (daphne.klemme@yale.edu) for zoom information.