A SNAIL-mediated Cascaded Random Access Quantum Memory (Part 2)

Multimode superconducting cavities are promising building blocks for realizing hardware-efficient quantum memories. In the first of these two talks, we presented an implementation of a Cascaded Random Access Quantum Memory (C-RAQM) [1]. This architecture protects long-lived bosonic modes of the multimode quantum memory from ancilla-induced errors, by first interfacing it to a buffer cavity via a SNAIL coupler. The buffer, serving as a cache memory, is in turn controlled by a transmon ancilla. When optimally biased with a DC magnetic flux, the SNAIL provides a cubic nonlinearity while minimizing quartic interactions. This enables microwave-activated beam-splitter operations via three-wave mixing, which drive SWAP gates between mode pairs, while mitigating inter-mode crosstalk.

In this second talk, we present experimental progress on operating the device as a memory: SNAIL-activated state transfer between arbitrary buffer-memory pairs drawn from two buffer modes and seven memory modes, and universal buffer-cavity control via transmon-mediated sideband interactions [2]. We also report progress toward inter-mode gate operations and toward entanglement generation and characterization using conditional buffer-memory beam-splitters.

[1] Z. Li, et al., arXiv:2503.13953 (2025).

[2] Huang, J. et al., arXiv:2503.10623 (2025).