- #1
dakshina gandikota
- 2
- 0
I have a question about HHL algorithm https://arxiv.org/pdf/0811.3171.pdf for solving linear equations of the form:
A x = b
Where A, x and b are matrices
Take for example
4x1 + 2x2 =14
5x1 + 3x2 = 19
HHL apply the momentum operator eiAτto/T on the state, do a Fourier Transform on |b> and *uncompute phase estimation*. I don't follow the last step. How can you uncompute, when you haven't computed the phase estimation?
Earlier in the paper they mention that let |u> be the eigen vector of |b> using phase estimation. Is this what they are referring to? There is no circuit to back their algorithm in that pdf.
I also checked a particular implementation of HHL https://arxiv.org/pdf/1110.2232v2.pdf where they mention
"Apply the quantum inverse Fourier transform to the register C. Denote the basis states after quantum Fourier transform as |k>"
It seems they didn't edit the sentence properly. So not much help.
Does anyone think these are not properly described in the papers? By the way, there has been a thread https://quantumcomputing.stackexcha...systems-of-equations-hhl09-step-2-preparation to discuss the paper but not address the specific issues.
Thanks
A x = b
Where A, x and b are matrices
Take for example
4x1 + 2x2 =14
5x1 + 3x2 = 19
HHL apply the momentum operator eiAτto/T on the state, do a Fourier Transform on |b> and *uncompute phase estimation*. I don't follow the last step. How can you uncompute, when you haven't computed the phase estimation?
Earlier in the paper they mention that let |u> be the eigen vector of |b> using phase estimation. Is this what they are referring to? There is no circuit to back their algorithm in that pdf.
I also checked a particular implementation of HHL https://arxiv.org/pdf/1110.2232v2.pdf where they mention
"Apply the quantum inverse Fourier transform to the register C. Denote the basis states after quantum Fourier transform as |k>"
It seems they didn't edit the sentence properly. So not much help.
Does anyone think these are not properly described in the papers? By the way, there has been a thread https://quantumcomputing.stackexcha...systems-of-equations-hhl09-step-2-preparation to discuss the paper but not address the specific issues.
Thanks