Variational Quantum Algorithms
for Optimizing Probe States
B.C. Oudejans (TU Delft - Applied Sciences)
Johannes Borregaard – Mentor (TU Delft - QN/Borregaard groep)
D. de Laat – Mentor (TU Delft - Discrete Mathematics and Optimization)
J.M. Thijssen – Graduation committee member (TU Delft - QN/Thijssen Group)
W.G.M. Groenevelt – Graduation committee member (TU Delft - Analysis)
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Abstract
As quantum computers are developing, they are beginning to become useful for practical applications, for example in the field of quantum metrology. In this work, a variational quantum algorithm is used to find an optimal probe state for measuring parameters in a noisy environment. This is achieved by optimizing a cost on a quantum computer, based on the Fisher information of the parameters to be estimated. These parameters are then estimated using maximum likelihood estimators. In a simulation, a probe state was found that performed better than the best possible state for noiseless measurements, although this could not be reproduced on an actual quantum computer.