The coherent control of interacting spins in semiconductor quantum dots is of strong interest for quantum information processing and for studying quantum magnetism from the bottom up. Here we present a 2 × 4 germanium quantum dot array with full and controllable interactions between nearest-neighbour spins. As a demonstration of the level of control, we define four singlet–triplet qubits in this system and show two-axis single-qubit control of each qubit and SWAP-style two-qubit gates between all neighbouring qubit pairs, yielding average single-qubit gate fidelities of 99.49(8)–99.84(1)% and Bell state fidelities of 73(1)–90(1)%. Combining these operations, we experimentally implement a circuit designed to generate and distribute entanglement across the array. A remote Bell state with a fidelity of 75(2)% and concurrence of 22(4)% is achieved. These results highlight the potential of singlet–triplet qubits as a competing platform for quantum computing and indicate that scaling up the control of quantum dot spins in extended bilinear arrays can be feasible.@en

Quantum systems with engineered Hamiltonians can be used to study many-body physics problems to provide insights beyond the capabilities of classical computers. Semiconductor gate-defined quantum dot arrays have emerged as a versatile platform for realizing generalized Fermi-Hubbard physics, one of the richest playgrounds in condensed matter physics. In this work, we employ a germanium 4×2 quantum dot array and show that the naturally occurring long-range Coulomb interaction can lead to exciton formation and transport. We tune the quantum dot ladder into two capacitively coupled channels and exploit Coulomb drag to probe the binding of electrons and holes. Specifically, we shuttle an electron through one leg of the ladder and observe that a hole is dragged along in the second leg under the right conditions. This corresponds to a transition from single-electron transport in one leg to exciton transport along the ladder. Our work paves the way for the study of excitonic states of matter in quantum dot arrays.

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Lithium argyrodite solid electrolytes have attracted ever-increasing attention for all-solid-state batteries due to their high ionic conductivity and low cost. However, the relation between structure and ionic transport for the halogen-rich lithium argyrodites under different synthesis routes is still elusive. Herein, the influence of synthesis procedures, such as annealing conditions and balling milling, on the structure, ionic conductivity, and activation energy of the lithium argyrodite (e.g., Li_5.5PS_4.5Cl_1.5, Li_5.3PS_4.3Cl_1.7), is systematically investigated. Compared with high-energy ball milling followed by annealing, using fast dry mixing followed by annealing can obtain comparable ionic conductivity of the chlorine-rich lithium argyrodites. Single-crystal LiNi_0.83Co_0.11Mn_0.06O₂-based solid-state battery with these electrolytes shows stable cycling performance, demonstrating that chlorine-rich lithium argyrodite is a promising candidate for all-solid-state batteries.

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