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State

Polynomial approximation

Chebyshev coefficients, a degree, and the bound the polynomial obeys before anyone rescales it. The degree is the query count a circuit will pay, so this is where an error budget turns into a runtime.

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Work that arrives here

  • Polynomial approximation

    Given a target function, a domain and an error ε\varepsilon, return a polynomial of definite parity, bounded on [1,1][-1,1], that is ε\varepsilon-close to the target on that domain, with an explicit degree.

Work that starts here

  • QSP phase factors

    Given an admissible polynomial, compute the phase sequence ΦΦ that makes the quantum-signal-processing product reproduce it to accuracy ε\varepsilon in classical finite-precision arithmetic.