Spin-based quantum processors in silicon quantum dots offer high-fidelity single and two-qubit operation. Recently multi-qubit devices have been realized; however, many-qubit demonstrations remain elusive, partly due to the limited qubit-to-qubit connectivity. These problems can be overcome by using SWAP gates, which are challenging to implement in devices having large magnetic field gradients. Here we use a primitive SWAP gate to transfer spin eigenstates in 100 ns with a fidelity of \({\bar{F}}_{{\rm{SWAP}}}^{{\rm{(p)}}}=98 \%\). By swapping eigenstates we are able to demonstrate a technique for reading out and initializing the state of a double quantum dot without shuttling charges through the quantum dot. We then show that the SWAP gate can transfer arbitrary two-qubit product states in 300 ns with a fidelity of \({\bar{F}}_{{\rm{SWAP}}}^{{\rm{(c)}}}=84 \%\). This work sets the stage for many-qubit experiments in silicon quantum dots.

硅量子点中基于自旋的量子处理器可提供高保真单量子点和二量子比特操作。最近已经实现了多量子位设备。但是，许多量子比特的演示仍然难以捉摸，部分原因是量子比特到量子比特之间的连通性有限。这些问题可以通过使用SWAP门来克服，而SWAP门在具有大磁场梯度的设备中难以实现。在这里，我们使用原始SWAP门以保真度为\（{\ bar {F}} _ {{\ rm {SWAP}}} ^ {{\ rm {（p）}} = 98 \％\）。通过交换本征态，我们能够演示一种用于读取和初始化双量子点状态的技术，而无需通过量子点穿梭电荷。然后，我们证明了SWAP门可以在300 ns内以\（{\ bar {F}} _ {{\ rm {SWAP}}} ^ {{\ rm {（c） }}} = 84 \％\）。这项工作为硅量子点中的多量子位实验奠定了基础。