2026/04/07 by Akoramurthy B, Surendiran. B · 1 voice
Physics and Astronomy · #quant-ph
Quantum phase estimation~(QPE) is central to numerous quantum algorithms, yet its standard implementation demands an \calO(m2)-gate quantum Fourier transform~(QFT) on m control qubits-a prohibitive overhead on near-term noisy intermediate-scale quantum (NISQ) devices. We introduce the Phase-Fidelity-Aware Truncated QFT (PFA-TQFT), a family of approximate QFT circuits parameterised by a truncation depth~d that omits controlled-phase rotations below a hardware-calibrated fidelity threshold~\eps. Our central result establishes \TV(Pφ,Pφd)≤π(m-d)/2d, showing that for d=\calO(log m) circuit size collapses from \calO(m2) to \calO(mlog m) while estimation error grows by at most \calO(2-d). We characterise \dstar=\Floorlog2(2π/\eps2q) directly from native gate fidelities, demonstrating 31.3 -43.7% at m = 30, gate-count reduction on IBM Eagle/Heron and IonQ~Aria with negligible accuracy loss. Numerical experiments on the transverse-field Ising model confirm all theoretical predictions and reveal a noise-truncation synergy: PFA-TQFT outperforms full QFT under NISQ noise \eps2q\gtrsim 2×10-3.