2025/08/29 by Yuan Lü, Lu, Yao-Cheng, Han-Hsuan Lin +1
Computer Science · Materials Science · #Chemical and Physical Properties of Materials #FOS: Physical sciences #Quantum Computing Algorithms and Architecture #Quantum Information and Cryptography #Quantum Physics (quant-ph)
paper · pdf · doi:10.48550/arxiv.2508.21346
openalex publication_date 2025/08/29 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Quantum state preparation (QSP) is a key component in many quantum algorithms. In particular, the problem of sparse QSP (SQSP) \unicodex2013 the task of preparing the states with only a small number of non-zero amplitudes \unicodex2013 has garnered significant attention in recent years. In this work, we focus on reducing the circuit depth of SQSP with limited number of ancilla qubits. We present two SQSP algorithms: one with depth O(nlog d), and another that reduces depth to O(n). The latter leverages mid-circuit measurement and feedforward, where intermediate measurement outcomes are used to control subsequent quantum operations. Both constructions have size O(dn) and use O(d) ancilla qubits. Compared to the state-of-the-art SQSP algorithm in arXiv:2108.06150, which allows an arbitrary number of ancilla qubits m>0, both of our algorithms achieve lower circuit depth when m=d.