Amplitude estimation without phase estimation

Understand

This paper focuses on the quantum amplitude estimation algorithm, which is a core subroutine in quantum computation for various applications.

• The conventional approach for amplitude estimation is to use the phase estimation algorithm, which consists of many controlled amplification operations followed by a quantum Fourier transform.
• However, the whole procedure is hard to implement with current and near-term quantum computers.
• In this paper, we propose a quantum amplitude estimation algorithm without the use of expensive controlled operations; the key idea is to utilize the maximum likelihood estimation based on the combined measurement data produced from quantum circuits with different numbers of amplitude amplification operations.