Variational Quantum Fidelity Estimation
- Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
- California Institute of Technology (CalTech), Pasadena, CA (United States)
Computing quantum state fidelity will be important to verify and characterize states prepared on a quantum computer. In this work, we propose novel lower and upper bounds for the fidelity F ( ρ , σ ) based on the ``truncated fidelity'' F ( ρ m , σ ) , which is evaluated for a state ρ m obtained by projecting ρ onto its m -largest eigenvalues. Our bounds can be refined, i.e., they tighten monotonically with m . To compute our bounds, we introduce a hybrid quantum-classical algorithm, called Variational Quantum Fidelity Estimation, that involves three steps: (1) variationally diagonalize ρ , (2) compute matrix elements of σ in the eigenbasis of ρ , and (3) combine these matrix elements to compute our bounds. Our algorithm is aimed at the case where σ is arbitrary and ρ is low rank, which we call low-rank fidelity estimation, and we prove that no classical algorithm can efficiently solve this problem under reasonable assumptions. Finally, we demonstrate that our bounds can detect quantum phase transitions and are often tighter than previously known computable bounds for realistic situations.
- Research Organization:
- Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
- Sponsoring Organization:
- National Science Foundation (NSF); US Air Force Office of Scientific Research (AFOSR); USDOE Office of Science (SC), Basic Energy Sciences (BES). Materials Sciences & Engineering Division
- Grant/Contract Number:
- 89233218CNA000001
- OSTI ID:
- 1659189
- Report Number(s):
- LA-UR--19-25585
- Journal Information:
- Quantum, Journal Name: Quantum Vol. 4; ISSN 2521-327X
- Publisher:
- Quantum Science Open CommunityCopyright Statement
- Country of Publication:
- United States
- Language:
- English
Variational quantum algorithms
|
journal | August 2021 |
Variational quantum algorithm for estimating the quantum Fisher information
|
journal | February 2022 |
| Variational quantum Gibbs state preparation with a truncated Taylor series | text | January 2020 |
| Reformulation of the No-Free-Lunch Theorem for Entangled Data Sets | text | January 2020 |
| Quantum Algorithm for Fidelity Estimation | text | January 2021 |
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