Universal control of four singlet-triplet qubits

Area of Science:

• Quantum Computing
• Quantum Information Processing
• Semiconductor Spintronics

Background:

• Coherent control of interacting spins in semiconductor quantum dots is crucial for quantum information processing and quantum magnetism.
• Developing scalable quantum computing platforms requires precise control over individual quantum systems.

Purpose of the Study:

• To demonstrate full and controllable interactions between nearest-neighbor spins in a 2x4 germanium quantum dot array.
• To showcase the potential of singlet-triplet qubits for quantum computing applications.

Main Methods:

• Fabrication of a 2x4 germanium quantum dot array.
• Definition and manipulation of four singlet-triplet qubits.
• Implementation of two-axis single-qubit gates and SWAP-style two-qubit gates between neighboring qubits.
• Experimental execution of a circuit for entanglement generation and distribution.

Main Results:

• Achieved high average single-qubit gate fidelities (99.49(8)-99.84(1)%) and Bell state fidelities (73(1)-90(1)%).
• Successfully generated and distributed entanglement, achieving a remote Bell state with 75(2)% fidelity and 22(4)% concurrence.
• Demonstrated the feasibility of scaling up quantum dot spin control in extended bilinear arrays.

Conclusions:

• Singlet-triplet qubits in germanium quantum dots represent a promising platform for quantum computing.
• Scalable control of quantum dot spins in extended arrays is achievable, advancing the development of quantum technologies.