Transversal operations reduce communication in distributed quantum computing
Transversal Fanout for Fault Tolerant Distributed Quantum Computing: Analysis and Application
Distributed, Parallel, and Cluster Computing
Summary
Fanout operations let one quantum bit control many others at different locations, but doing this safely and efficiently in error-corrected quantum computers is tricky and usually needs lots of communication between computers. The authors show a way to do these fanouts using special code properties and transversal gates that work across multiple quantum computers connected together. They test their ideas on a particular error-correcting code and analyze how many basic steps, entangled states, and helper qubits are needed. This helps make big fanout operations easier and more practical across separate quantum processors.
What this means in practice
- •For quantum hardware engineers: Construct distributed quantum circuits with fewer non-local operations using transversal fanout to improve fault tolerance and efficiency.
- •For quantum network designers: Implement large-scale quantum fanout across networked quantum processors with reduced communication overhead enabled by transversal gate techniques.
Authors
Seng W. Loke
Abstract
We study a resource-efficient approach for implementing logical fanout operations in fault-tolerant distributed quantum computing using transversal operations on quantum error-correcting code blocks. Logical fanout, comprising multiple controlled-NOT operations from a common control qubit to target qubits located at remote nodes, is an important primitive for distributed quantum computation but can require substantial non-local communication when implemented directly between encoded blocks. We exploit the structure of encoded blocks and the availability of transversal logical operations to construct distributed fanout circuits that reduce the required non-local operations while preserving the logical action of the fanout operation. The construction is developed for encoded quantum information and illustrated using Bivariate Bicycle (BB)-code blocks. We analyze the resulting physical gate, entanglement, circuit-depth, and ancilla requirements. The approach provides a systematic method for implementing large logical fanout operations across distributed error-corrected quantum processors. Also, we study a distributed implementation of the global gate GCZ involving logical qubits (encoded using BB-code blocks), exploiting the concurrency in transversal distributed fanouts.