A 2x2 quantum dot array with controllable inter-dot tunnel couplings

TL;DR

This paper reports the creation of a controllable 2x2 quantum dot array in a 2D lattice, enabling tunable inter-dot couplings and fast spin readout, advancing quantum simulation capabilities.

Contribution

It introduces a 2x2 quantum dot array with independently tunable tunnel couplings and demonstrates fast spin state readout, expanding quantum dot platforms to two-dimensional systems.

Findings

Achieved dynamic control of charge occupation in each dot.

Tuned nearest-neighbor tunnel couplings from 0 to 40 μeV.

Performed fast single-shot spin readout (~1 μs) using spin-to-charge conversion.

Abstract

The interaction between electrons in arrays of electrostatically defined quantum dots is naturally described by a Fermi-Hubbard Hamiltonian. Moreover, the high degree of tunability of these systems make them a powerful platform to simulate different regimes of the Hubbard model. However, most quantum dot array implementations have been limited to one-dimensional linear arrays. In this letter, we present a square lattice unit cell of 2$\times$2 quantum dots defined electrostatically in a AlGaAs/GaAs heterostructure using a double-layer gate technique. We probe the properties of the array using nearby quantum dots operated as charge sensors. We show that we can deterministically and dynamically control the charge occupation in each quantum dot in the single- to few-electron regime. Additionally, we achieve simultaneous individual control of the nearest-neighbor tunnel couplings over a range 0-40~$\mu$eV. Finally, we demonstrate fast ($\sim 1$~$\mu$s) single-shot readout of the spin state of electrons in the dots, through spin-to-charge conversion via Pauli spin blockade. These advances pave the way to analog quantum simulations in two dimensions, not previously accessible in quantum dot systems.