A four-qubit germanium quantum processor

Area of Science:

• Quantum Computing
• Semiconductor Physics
• Materials Science

Background:

• Quantum dots offer a promising platform for quantum information processing due to their compatibility with semiconductor manufacturing.
• Previous research demonstrated two-qubit logic in various materials, but scaling to larger qubit numbers remains a challenge.
• Interconnecting multiple qubits in semiconductor devices is crucial for advancing quantum technologies.

Purpose of the Study:

• To demonstrate a scalable four-qubit quantum processor.
• To investigate controllable coupling in a two-by-two array of quantum dots.
• To implement all-electrical qubit logic and programmable multi-qubit operations.

Main Methods:

• Fabrication of a four-qubit quantum processor using hole spins in germanium quantum dots arranged in a two-by-two array.
• Implementation of all-electrical qubit logic and pulsed exchange interactions for programming.
• Execution of a quantum logic circuit to generate a four-qubit Greenberger-Horne-Zeilinger state.
• Incorporation of dynamical decoupling to achieve coherent evolution.

Main Results:

• Demonstration of a compact and highly connected four-qubit quantum processor.
• Controllable coupling achieved along both directions in the two-by-two quantum dot array.
• Successful execution of one-, two-, three-, and four-qubit operations.
• Generation of a four-qubit Greenberger-Horne-Zeilinger state with coherent evolution.

Conclusions:

• The developed germanium quantum dot processor represents a significant step towards scalable quantum computing.
• All-electrical control and programmable operations pave the way for complex quantum circuits.
• This work advances the potential for quantum error correction and quantum simulation using semiconductor-based quantum dots.