Weakly measured while loops: peeking at quantum states. (1st April 2022)

• Record Type: Journal Article
• Authors: Andrés-Martínez, Pablo; Heunen, Chris
• Is Part Of: Quantum science and technology. Volume 7:Number 2(2022)
• Publication Date: 2022-04-01
• Subjects: programming primitive -- while loop -- weak measurement; Quantum theory -- Periodicals; Quantum theory; Periodicals; 530
• DOI: 10.1088/2058-9565/ac47f1
• Languages: English
• ISSNs: 2058-9565

Abstract

Abstract: A while loop tests a termination condition on every iteration. On a quantum computer, such measurements perturb the evolution of the algorithm. We define a while loop primitive using weak measurements, offering a trade-off between the perturbation caused and the amount of information gained per iteration. This trade-off is adjusted with a parameter set by the programmer. We provide sufficient conditions that let us determine, with arbitrarily high probability, a worst-case estimate of the number of iterations the loop will run for. As an example, we solve Grover's search problem using a while loop and prove the quadratic quantum speed-up is maintained.