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Q: Fachverband Quantenoptik und Photonik
Q 45: Mechanical, Macroscopic, and Continuous-variable Quantum Systems (joint session QI/Q)
Q 45.2: Vortrag
Mittwoch, 12. März 2025, 15:00–15:15, HS IX
Macroscopic quantum sizes of mechanical systems — •Benjamin Yadin1 and Matteo Fadel2 — 1Naturwissenschaftlich-Technische Fakultät, Universität Siegen, Walter-Flex-Straße 3, 57068 Siegen, Germany — 2Department of Physics, ETH Zürich, 8093 Zürich, Switzerland
Whether quantum theory holds true in the macroscopic realm -- or breaks down at some size scale -- is unknown. Many experimental platforms are probing this question by creating quantum states of ever-increasing size, for example with high masses or involving entanglement between many particles. Measures of `macroscopicity' are designed to quantify the extent to which a system displays quantum behaviour at a large scale; however, these are often difficult to clearly interpret or fail to apply to a large variety of systems and states.
Here, we propose two measures corresponding to properties originally identified as crucial by Leggett: the `extensive size', measuring the spread of quantum coherence over a physical size scale; and the `entangled size', quantifying many-body entanglement between constituent parts of the system. These measures are mathematically well-defined for any state and lower bounds are readily obtainable from experimental data. We demonstrate this through application to mechanical systems -- using data from mechanical oscillators and molecular interferometers. As part of this, we show the dependence on temperature of many-body entanglement between atoms in an oscillator.
Keywords: macroscopic quantum states; many-body entanglement; quantum oscillators