Entanglement of an array of massive, magnetically levitated superconducting microparticles on a chip

Project Information

SuperQLev

Grant agreement ID: 101087847

DOI

10.3030/101087847

EC signature date 23 March 2023

Start date 1 January 2024

End date 31 December 2028

Funded under

• European Research Council (ERC)

Total cost

€ 2 000 000,00

EU contribution

€ 2 000 000,00

Coordinated by

CHALMERS TEKNISKA HOGSKOLA AKTIEBOLAG
Sweden

Periodic Reporting for period 1 - SuperQLev (Entanglement of an array of massive, magnetically levitated superconducting microparticles on a chip)

Reporting period: 2024-01-01 to 2026-06-30

Summary of the context and overall objectives of the project

Quantum states of massive objects have fascinated us since the inception of quantum mechanics. Nowadays molecules of thousands of atoms and nanomechanical resonators weighing picogram can be brought into quantum states. This capability enables tests of the validity of quantum mechanics and provides new avenues for quantum sensing technologies. Entangled states are particularly relevant in this context as they unlock multipartite quantum correlations that, amongst others, enable precise measurements beyond the standard quantum limit and novel tests for the interplay between quantum mechanics and gravity. However, no experiment to date demonstrated entanglement between the motion of microparticles, which would access a novel parameter regime in terms of mass, quantum correlation, and particle number. SuperQLev will fill this gap and demonstrate entanglement of the center-of-mass motion of an array of magnetically levitated superconducting microparticles on chip. This achievement will break new ground by exploring multipartite quantum states of massive objects. SuperQLev will make this possible by merging two technologies into a unique experimental platform. The first technology is magnetic levitation of superconducting microparticles, which offers the capability of levitating massive particles with ultralow mechanical dissipation. The second technology is superconducting quantum circuits that offer a versatile toolbox for quantum control. This hitherto unexplored hybrid quantum platform allows SuperQLev to conduct ground-breaking proof-of-principle experiments in quantum sensing and fundamental physics.

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

SuperQLev builds upon the technology of chip-based magnetic levitation of superconducting microparticles, which has been pioneered by us. We have further developed this technology by designing and fabricating chip-based magnetic traps that can levitate two microparticles. We used finite element method simulations to estimate the coupling rates between the motion of microparticles in these traps and obtain rates that are larger than the expected mechanical dissipation rate. This will allow us to observe an avoided crossing in trap frequency upon tuning of one of the traps, a key observation for our project. Furthermore, we investigated methods to reduce the adhesion force between a microparticle and the surface it is resting on, which enables more repeatable levitation at ultra-low temperatures. Further, we fabricated and characterized flux-tunable superconducting resonators that we aim to inductively couple to the center-of-mass motion of the levitated microparticles. Key in our design of the resonator is that it can efficiently measure flux signals with a measured transfer efficiency from the input coil to the resonator of up to 20%. The next step is to measure the flux signal that originates from the motion of the microparticles. All these technological developments feed into our project and build the base to demonstrate multiparticle levitation and to realize correlated quantum states of their motion.

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)

We have realized a method to reduce the adhesion of microparticles. This result is relevant to other research fields, where it is crucial to reduce the adhesion force of microparticles, such as chemistry, biochemistry, or materials science. Independently, we have demonstrated a simple superconducting flip-chip method, which can be easily realized in the laboratory, and can be relevant for superconducting quantum technologies.