Doubly Optimal Parallel Wire Cutting without Ancilla Qubits

作者：Hiroyuki Harada, Kaito Wada, Naoki Yamamoto · 发表于：PRX Quantum · 年份：2024 · DOI：10.1103/prxquantum.5.040308 · 被引用次数：22 · 研究领域：Quantum Computing Algorithms and Architecture、VLSI and Analog Circuit Testing、Cellular Automata and Applications

A restriction in the quality and quantity of available qubits presents a substantial obstacle to the application of near-term and early fault-tolerant quantum computers in practical tasks. To confront this challenge, some techniques for effectively augmenting the system size through classical processing have been proposed; one promising approach is quantum circuit cutting. The main idea of quantum circuit cutting is to decompose an original circuit into smaller subcircuits and combine outputs from these subcircuits to recover the original output. Although this approach enables us to simulate larger quantum circuits beyond physically available circuits, it needs classical overheads quantified by two metrics: the sampling overhead in the number of measurements to reconstruct the original output, and the number of channels in the decomposition. Thus, it is crucial to devise a decomposition method that minimizes both of these metrics, thereby reducing the overall execution time. This paper studies the problem of decomposing the n -qubit identity channel, i.e., n -parallel wire cutting, into a set of local operations and classical communication; then we give an optimal wire-cutting method composed of channels based on mutually unbiased bases that achieves minimal overheads in both the sampling overhead and the number of channels, without ancilla qubits. This is in stark contrast to the existing method that achieves the optimal sampling overhead yet with ancilla qubits....