Quantum Dot Fermi-Hubbard Emulators

Project Information

QuDoFH

Grant agreement ID: 882848

DOI

10.3030/882848

Project closed

EC signature date 6 May 2020

Start date 1 September 2020

End date 31 January 2026

Funded under

• EXCELLENT SCIENCE - European Research Council (ERC)

Total cost

€ 3 449 720,00

EU contribution

€ 3 449 720,00

Coordinated by

TECHNISCHE UNIVERSITEIT DELFT
Netherlands

Periodic Reporting for period 3 - QuDoFH (Quantum Dot Fermi-Hubbard Emulators)

Reporting period: 2023-09-01 to 2025-02-28

Summary of the context and overall objectives of the project

The behavior of interacting electrons has led to many puzzles in condensed matter physics, ranging from superconductivity to exotic forms of magnetism. These puzzles are hard to solve because the complexity of interacting electrons cannot be captured by analytical or numerical methods. Quantum simulation holds promise to significantly further our insight into correlated electrons systems by emulating the relevant physics in well-controlled experimental model system. Furthermore, such experiments may produce predicted phases of matter that were not previously observed and can even uncover completely new phases of matter. In the QuDoFH ERC project, we will employ semiconductor technology as a novel approach to build highly versatile and powerful model systems.

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

We have achieved several scientific breakthroughs in the context of quantum dot Fermi-Hubbard simulator. We studied quantum magnetism with our simulator by successfully forming a Heisenberg spin chain by setting homogeneous exchange couplings in a linear four-dot array and probing the antiferromagnetic ground state by performing singlet-triplet correlation measurements. The simultaneous control of multiple exchange couplings, and the preparation and characterization of many-body spin states shown in this work set the ground for simulating exotic phases such as resonating valence bonds and quantum spin liquid. We are now probing such physics in a 4x2 quantum dot ladder device.
Furthermore, we measured the long-range Coulomb interaction in a six-dot array and investigated its application in simulating artificial atoms and molecules. Finally, in another 4x2 quantum dot ladder device, we exploit the long-range Coulomb interaction to form excitons (bound electron-hole pairs). Under the right conditions, an electron propagating through one leg of the ladder controlled by gate voltage pulses, drags along a hole traveling through the other leg.
Quantum dot ladders are a key component of the QuDoFH project. The scientific results we have shown in the grant period established the capabilities of quantum-dot arrays as a promising Fermi-Hubbard simulator.

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)

Following earlier work with quantum dot arrays where either the on-site interaction energy or the hopping term of the Fermi-Hubbard model dominated, in the first work carried out under the ERC the exchange energy dominated, which is the smallest energy scale and hence the most difficult to use and probe. In the second line of research the long-range interaction energy was mapped out and exploited. This interaction is not present in some alternative quantum simulation platforms, but is highly relevant in real physical systems.
In the coming years, we expect to explore not on square ladders but also triangular ladders, and we will also further extend the size of the ladders, as planned in the proposal.

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