Se p 19 99 A Fault - Tolerant Superconducting Associative Memory

The demand for high-density data storage with ultrafast accessibility motivates the search for new memory implementations. Ideally such storage devices should be robust to input error and to unreliability of individual elements; furthermore information should be addressed by its content rather than by its location. Here we present a concept for an associative memory whose key component is a superconducting array with natural multiconnectivity. Its intrinsic redundancy is crucial for the content-addressability of the resulting storage device and also leads to parallel image retrieval. Because patterns are stored non-locally both physically and logically in the proposed device, information access and retrieval are fault-tolerant. This superconducting memory should exhibit picosecond single-bit acquisition times with negligible energy dissipation during switching and multiple non-destructive read-outs of the stored data. The key component of our proposed associative memory is a superconducting array with multiple interconnections (Figure 1), where each bit is represented by a wire and thus is physically delocalized. More specifically this network consists of a stack of two perpendicular sets of N parallel wires separated by a thin oxide layer. 1,2 At low temperatures a superconductor-insulator-superconductor layered structure, known as a Josephson junction, 3,4 exists at each node of this array; logically each pattern in our proposed memory is stored nonlocally in these N 2 interconnections. We note that in this network each horizontal/vertical wire is coupled to each vertical/horizontal one by a Josephson junction so that in the thermodynamic 1