Comparing quantum codes for fault-tolerant distributed quantum computing
Encoding and Node Choices in Transversal Fault-Tolerant Distributed Quantum Computations: An Initial Study
Distributed, Parallel, and Cluster Computing
Summary
Quantum computers use special codes to protect information from errors during calculations. This paper looks at different ways of encoding quantum information and how to choose nodes for performing quantum operations across multiple locations. The authors find that using fewer entangled pairs to link parts of the system isn't always the best way to reduce errors. Instead, selecting codes with stronger error protection, even if they use more resources, can lead to more reliable distributed quantum computations.
What this means in practice
- •For quantum hardware engineers: Optimize code and node choices to reduce logical error rates in distributed quantum processors performing transversal non-local gates.
- •For quantum algorithm developers: Design distributed quantum algorithms that leverage concurrent logical operations enabled by specific code encodings like the BB code.
Authors
Seng W. Loke
Abstract
We compare and study different Bivariate-Bicycle (BB) encodings and node choices for distributed quantum operations such as transversal non-local CNOTs. We observe that while some encodings have more physical qubits requiring more ebits for a distributed computation, reducing ebit consumption alone might not be the best criterion for selecting an encoding for the logical qubits, if the goal is to reduce the logical error rate of the distributed computation; for example, one should also consider encodings with a larger distance, which using more physical qubits can provide. We consider distributed, or non-local, CNOTs and computation of the global gate (GCZ) over distributed logical qubits as examples. The choice of encoding enables particular concurrent operations; e.g., we show that a transversal physical GCZ on a self-dual $[[120,8,12]] BB$ code can realize eight concurrent logical GCZ operations after accounting for the logical permutation induced by transversal Hadamard.