Universal control of four singlet-triplet qubits

Kavli Affiliate: Menno Veldhorst

| First 5 Authors: Xin Zhang, Elizaveta Morozova, Maximilian Rimbach-Russ, Daniel Jirovec, Tzu-Kan Hsiao

| Summary:

The coherent control of interacting spins in semiconductor quantum dots is of
strong interest for quantum information processing as well as for studying
quantum magnetism from the bottom up. On paper, individual spin-spin couplings
can be independently controlled through gate voltages, but nonlinearities and
crosstalk introduce significant complexity that has slowed down progress in
past years. Here, we present a $2times4$ germanium quantum dot array with full
and controllable interactions between nearest-neighbor 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 all qubits and SWAP-style
two-qubit gates between all neighbouring qubit pairs. Combining these
operations, we experimentally implement a circuit designed to generate and
distribute entanglement across the array. 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.

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