Scalable quantum random-access memory with superconducting circuits

Leszek Jaroszynski

Shen, Fanhao, Ji, Yujie, Xiang, Debin +20 more

Quantum random access memory (QRAM) enables efficient classical data access for quantum computers -- a prerequisite for many quantum algorithms to achieve quantum speedup. Despite various proposals, the experimental realization of QRAM remains largely unexplored. Here, we experimentally investigate the circuit-based bucket-brigade QRAM with a superconducting quantum processor. To facilitate the experimental implementation, we introduce a hardware-efficient gate decomposition scheme for quantum routers, which effectively reduces the depth of the QRAM circuit by more than 30% compared to the conventional controlled-SWAP-based implementation. We further propose an error mitigation method to boost the QRAM query fidelity. With these techniques, we are able to experimentally implement the QRAM architectures with two and three layers, achieving query fidelities up to 0.800 $\pm$ 0.026 and 0.604$\pm$0.005, respectively. Additionally, we study the error propagation mechanism and the scalability of our QRAM implementation, providing experimental evidence for the noise resilience nature of the bucket-brigade QRAM architecture. Our results highlight the potential of superconducting quantum processors for realizing a scalable QRAM architecture.

K. C. Chen, Wenhan Dai, Carlos Errando-Herranz +2 more

A quantum random access memory (qRAM) is considered an essential computing unit to enable polynomial speedups in quantum information processing.Proposed implementations include the use of neutral atoms and superconducting circuits to construct a binary tree but these systems still require demonstrations of the elementary components.Here, we propose a photonic-integrated-circuit (PIC) architecture integrated with solid-state memories as a viable platform for constructing a qRAM.We also present an alternative scheme based on quantum teleportation and extend it to the context of quantum networks.Both implementations realize the two key qRAM operations, (1) quantum state transfer and (2) quantum routing, with already demonstrated components: electro-optic modulators, a Mach-Zehnder interferometer (MZI) network, and nanocavities coupled to artificial atoms for spin-based memory writing and retrieval.Our approaches furthermore benefit from built-in error detection based on photon heralding.Detailed theoretical analysis of the qRAM efficiency and query fidelity shows that our proposal presents viable near-term designs for a general qRAM.

Joseph Suttle, Neereja Sundaresan, Srikanth J. Srinivasan +10 more

Matthias Steffen

Kevin C. Chen, Wenhan Dai, Carlos Errando-Herranz +2 more

We propose a scalable photonic integrated circuit implementation of a heralded quantum random access memory and analyze its theoretical operation fidelity and efficiency.