Deterministic Ground State Preparation via Power-Cosine Filtering of Time Evolution Operators

TL;DR

This paper introduces a non-variational, efficient quantum protocol for deterministic ground state preparation using Power-Cosine filtering, minimizing hardware resources and outperforming traditional methods.

Contribution

The authors develop a novel Power-Cosine quantum signal processing method that simplifies implementation and enhances efficiency in preparing quantum many-body ground states.

Findings

Achieves exponential excited state suppression with circuit depth scaling as O(Δ^{-2} log(1/ε))

Validated through numerical simulations on the 1D Heisenberg XYZ model

Outperforms standard Trotterized Adiabatic State Preparation at similar circuit depths

Abstract

The deterministic preparation of quantum many-body ground states is essential for advanced quantum simulation, yet optimal algorithms often require prohibitive hardware resources. Here, we propose a highly efficient, non-variational protocol for ground state preparation using a Power-Cosine quantum signal processing (QSP) filter. By eschewing complex block-encoding techniques, our method directly utilizes coherent time-evolution operators controlled by a single ancillary qubit. The integration of mid-circuit measurement and reset (MCMR) drastically minimizes spatial overhead, translating iterative non-unitary filtering into deep temporal coherence. We analytically demonstrate that this approach achieves exponential suppression of excited states with a circuit depth scaling of $\mathcal{O}(\Delta^{-2}\log(1/\epsilon))$, where $\Delta$ denotes the spectral gap, prioritizing implementational simplicity over optimal asymptotic complexity. Numerical simulations on the 1D Heisenberg XYZ model validate the theoretical soundness and shot-noise resilience of our method. Furthermore, an advantage analysis reveals that our protocol exponentially outperforms standard Trotterized Adiabatic State Preparation (TASP) at equivalent circuit depths. This single-ancilla framework provides a highly practical and deterministic pathway for many-body ground state preparation on Early Fault-Tolerant (EFT) quantum architectures.