Periodic Reporting for period 2 - GUANTUM (Probing the limits of quantum mechanics and gravity with micromechanical oscillators)
Periodo di rendicontazione: 2023-04-01 al 2024-09-30
Quantum mechanics is a leading success story in physical science. Despite its success, it is incompatible with general relativity that describes gravity and the large-scale structure of the universe. This discrepancy is among the most pressing open questions of contemporary physics, or natural science in general. Contributions sheding light towards solving the problem are therefore of utmost importance to how mankind understands the functioning of our universe. The interface between quantum mechanics and general relativity has remained experimentally totally unaccessible, because only the most violent events in the universe have been considered to produce measurable effects due to the plausible quantum behavior of gravity. However, during recent years, possibly realizable laboratory tests touching this interface have been theoretically proposed. In this project, we experimentally probe the interface between quantum mechanics and gravity at an unprecedented scale by taking advantage of massive micromechanical systems, which can at the same time behave quantum-mechanically and exhibit gravitational interactions. The overarching goal is to create a system that exhibits nonlocal quantum correlations and gravity at the same time, paving the way for directly testing quantum gravity. The project also contributes to technological advances in precision measurements and in quantum information.
Feedback-based control of nano- and micromechanical resonators can enable the study of macroscopic quantum phenomena and also sensitive force measurements. We have experimentally demonstrated the feedback cooling macroscopic vibrating membrane close to its quantum ground state.
Dissipation and the accompanying fluctuations are often seen as detrimental for quantum systems, since they are associated with fast relaxation and loss of phase coherence. However, a pure quantum state can in principle be prepared if external noise induces suitable downwards transitions, while exciting transitions are blocked. We demonstrate such a refrigeration mechanism in a cavity optomechanical system, where we prepare a mechanical oscillator in its ground state by a noisy electromagnetic environment. intriguingly, one could use suitably filtered ambient noise for quantum state preparation.
In studies of quantum-mechanical somewhat massive systems, deep cryogenic temperatures close to absolute zero are basically necessary. The contemporary cooling technology, "cryogen-free" dilution refrigerators, utilizes cryocoolers which produce a massive amount of acoustic noise and vibrations. This is highly detrimental for any mechanical devices or sensors. The results will be of interest also to a broader community in fundamental research, in particular in detection of gravitational waves in large interferometers which are starting to use cryogenic systems. We have implemented an acoustic low-pass filter using massive copper blocks and ring springs inside a dilution refrigerator operating at 10 millikelvin temperatures. Our membrane resonators are now immune to the strong vibrations from the cryocooler, with a relatively simple and yet efficient acoustic filter.
Dissipation and the accompanying fluctuations are often seen as detrimental for quantum systems, since they are associated with fast relaxation and loss of phase coherence. However, a pure quantum state can in principle be prepared if external noise induces suitable downwards transitions, while exciting transitions are blocked. We demonstrate such a refrigeration mechanism in a cavity optomechanical system, where we prepare a mechanical oscillator in its ground state by a noisy electromagnetic environment. intriguingly, one could use suitably filtered ambient noise for quantum state preparation.
In studies of quantum-mechanical somewhat massive systems, deep cryogenic temperatures close to absolute zero are basically necessary. The contemporary cooling technology, "cryogen-free" dilution refrigerators, utilizes cryocoolers which produce a massive amount of acoustic noise and vibrations. This is highly detrimental for any mechanical devices or sensors. The results will be of interest also to a broader community in fundamental research, in particular in detection of gravitational waves in large interferometers which are starting to use cryogenic systems. We have implemented an acoustic low-pass filter using massive copper blocks and ring springs inside a dilution refrigerator operating at 10 millikelvin temperatures. Our membrane resonators are now immune to the strong vibrations from the cryocooler, with a relatively simple and yet efficient acoustic filter.
We will first measure the gravitational force between gold particles weighing a milligram, representing a new mass scale showing gravitational forces within a system. The main goal is to determine the effect of gravity on the quantum evolution of a massive object. We will develop strong quantum measurements in order to reach a situation where the positions of the gravitating masses exhibit significant quantum fluctuations, which includes preparing the gravitating masses in the ground state and in a squeezed state. Finally, we will attempt to create a system that exhibits nonlocal quantum correlations and gravity at the same time, paving the way for directly testing quantum gravity in a table-top setting.