Quantum Control of Gravity with Levitated Mechanics

Project Information

QuCoM

Grant agreement ID: 101046973

DOI

10.3030/101046973

Project closed

EC signature date 4 March 2022

Start date 1 October 2022

End date 31 March 2026

Funded under

• The European Innovation Council (EIC)

Total cost

€ 2 270 149,94

EU contribution

€ 2 270 149,94

Coordinated by

UNIVERSITA DEGLI STUDI DI TRIESTE
Italy

Periodic Reporting for period 1 - QuCoM (Quantum Control of Gravity with Levitated Mechanics)

Reporting period: 2022-10-01 to 2023-09-30

Summary of the context and overall objectives of the project

QuCoM objectives are to explore the interplay between quantum mechanics and gravity in the non-relativistic low energy regime. Supported and guided by theory, levitated mechanical experiments are used on the one hand to generate sensitive and quantum motional states by feedback control and on the other hand to perform sensitive force and acceleration experiments with levitated masses. Gravity measurements in two-mass configurations are one of the explored options.

On the theory side, we are using non-linear and out of equilibrium techniques for describing the motional state of levitated mechanical systems. This allows to analyse the observed motional effects in experiments and also for developing strategies for control and manipulation into relevant and interesting states such as squeezed states which are regarded as sensitivity increasing. Fundamental theory helps to put progression along QuCoM's objective into context of developing a deeper understanding of nature and its most fundamental description by quantum theory and general relativity. One core aspect of fundamental theory is to understand how gravity may influence the dynamics of quantum systems and gravity generated by quantum systems may appear to an external observer.

QuCoM experiments are based on levitated mechanics, including both optical dipole and Meissner magnetic traps. The particle size is between 100 nm and 1 mm in diameter and spans a huge mass range for exploration if new physics. The optical traps come with a high level of control by shaping and controlling light fields, while the Meissner traps are passive and ultimately sensitive to tiny force and acceleration effects. While the former are ideal for control experiments and for generating quantum states of motion, the later are seen as key to achieve sensitivities to detect the gravity generated by as small as a Planck mass.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

On the experimental side, we have performed magnetic levitation experiments of ferromagnets at Leiden and Southampton. We have performed optical levitation experiments at Southampton. We have implemented vibration isolation systems to reduce the effect of mechanical noise on the levitated systems. We are building a payload for a demonstration of optically levitated sensors in space. We have used the levitation systems to perform weak force measurements. We did experiments at Leiden on two-mass gravity on the attoNewton level and together with partners at Trento on magnetic field measurements at the femtoTesla level. We are working on using optical levitation systems to generate non-Gaussian states by a modulation protocol using cooling, squeezing, and non-linear effects.

On the theory side, we studied the dynamics of a levitated nanoparticle transitioning between harmonic and double-well potentials, considering thermal effects. We characterized the system thermodynamically using Wehrl entropy and explored time-dependent control in regimes with comparable quantum effects and thermal noise. Squeezing the initial state mitigated noise, we quantitatively assessed unitary and dissipative contributions to the control protocol. Regarding alternative (non-relativistic) models to quantum gravity, we studied: the Schrödinger-Newton equation, which posits a classical nature for gravity, causing deviations from standard quantum mechanics; the Károlyházy model for gravitational decoherence; the Diósi-Penrose model, according to which gravity induces the wave function collapse.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

On the experimental side, we have performed weak force sensing by using levitated sensors. the potential impact is for a new class of acceleration & gravity sensors in real world applications such as geology and space-based geodesy and earth observation for forecast and monitoring of weather and meteorological relevant processes. We have also used the squeezing operation to generate non-Gaussian states of motion in optical levitation traps and working on implementing a similar technique to Meissner magnetic traps.

On the theory side, the thermodynamical study of a levitated nanoparticle established a toolbox for simulating non-equilibrium processes, showing superior performance of quantum protocols in speed and accuracy. The study of non-standard quantum-gravitational models allowed to: find a way to enhance the effects induced by the Schrödinger-Newton dynamics in optomechanical platforms; generalize the Károlyházy model in order to make it compatible with experimental evidence; set an upper bound on the free parameters of the Diosi-Penrose model.