Enhancing the yield of bucket brigade quantum random access memory using redundancy repair

Area of Science:

• Quantum computing
• Quantum information science
• Fault-tolerant quantum computation

Background:

• Quantum random access memory (qRAM) is crucial for quantum algorithms, leveraging superposition for simultaneous data access.
• Quantum error correction (QEC) is necessary for qRAM operation but incurs significant resource overhead due to numerous physical qubits.
• Low-technology silicon nodes increase qubit density but also introduce defective qubits, reducing qRAM yield.

Purpose of the Study:

• To propose a novel quantum memory architecture that mitigates yield loss caused by defective qubits in qRAM.
• To address the resource overhead challenge associated with traditional QEC schemes in qRAM.
• To analyze the yield improvement of the proposed architecture under varying fabrication error rates.

Main Methods:

• Introduction of redundant qubits to compensate for defective qubits within the qRAM architecture.
• Analysis of yield improvement by simulating different fabrication error rates (0.5% to 1%) for varying numbers of logical qubits.
• Quantification of yield enhancement for a 1024-logical-qubit qRAM with eight redundant logical qubits.

Main Results:

• The proposed quantum memory architecture effectively compensates for defective qubits using redundant qubits.
• For a qRAM with 1024 logical qubits, the inclusion of eight redundant logical qubits resulted in a 95.92% yield improvement.
• The architecture demonstrates significant yield enhancement across various fabrication error rates and logical qubit counts.

Conclusions:

• The novel redundant qubit architecture offers a viable solution to improve qRAM yield and reliability.
• This approach effectively reduces the impact of defective qubits without substantially increasing resource overhead.
• The findings highlight a promising strategy for building more robust and scalable quantum random access memory.