A Cascaded Random-Access Quantum Memory in a 3D Multimode Cavity (Part II)

Random-access quantum memories (RAQM) offer a powerful resource for quantum computing by utilizing a single logic-capable quantum module with access to a register of memory modes. For RAQM to operate successfully, two key criteria must be met: (1) a quantum state stored in a memory mode must remain unaffected by operations on other memory modes, and (2) a gate performed on a memory mode must be insensitive to the states stored in other memory modes.

This is the second part of a two-part talk. Here, we assess the performance of our 3D multimode cavity as a RAQM. Our device includes a storage cavity layer containing high-coherence memory registers, managed by processor cavity and transmon layers. First, we benchmark beamsplitter interactions between modes in the storage and processor cavities, which serve as the foundation for storage and retrieval operations, achieving post-selected fidelity up to 99.9%. We then evaluate the sensitivity of these gates to the states stored in other storage modes, and vice versa. Finally, we benchmark the complete RAQM system by simultaneously storing information and performing serial operations across all storage modes.