QuTech360 w/ Xin Zhang: Universal control and benchmarking of four singlet-triplet qubits

In this QuTech360 Seminar, Xin Zhang is a postdoc researcher in the Vandersypen group, Quantum Computer Division at QuTech, presents Universal control and benchmarking of four singlet-triplet qubits. For the biography and abstract, please see the description below.
Title:
Universal control and benchmarking of four singlet-triplet qubits
Speaker:
Xin Zhang
Abstact:
The coherent control of interacting spins in semiconductor quantum dots is crucial for quantum information processing and studying quantum magnetism from the bottom up. In this work, we revisit the singlet-triplet qubit in germanium quantum dots and demonstrate universal control of 4 interacting singlet-triplet (S-T-) qubits with baseband-controlled pulses only. We achieve simultaneous initialization, individually control, and sequential measurement of four qubits at magnetic fields as low as 5 mT.
Our experiments show average singlet-qubit gate fidelities well above 99%, verified through randomized benchmarking. Additionally, we investigate swap-like two-qubit gate operations to entangle neighboring qubits, achieving Bell state fidelities ranging from 74% to 90%. By combining these operations, we successfully implement a circuit to generate and distribute entanglement across the array. This results in a remote Bell state between the endpoints of the quantum dot array with a fidelity of 75% and a concurrence of 22%. These findings highlight the potential of singlet-triplet qubits as a competing platform for quantum computing and indicate that scaling up the coherent control of quantum dot spins in extended bilinear arrays can be feasible.
Biography of Xin Zhang:
Xin Zhang is a postdoc researcher in the Vandersypen group at QuTech. He received his PhD degree in Physics at University of Science and Technology of China (2021), where he worked on measuring electron spin relaxation rates and spin-valley mixing in silicon quantum dots. Currently, he is investigating spin control and analog quantum simulation in a 2x4 germanium quantum dot array.
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