EURO 2024 Copenhagen
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4331. Quantum speedups for linear programming via interior point methods

Invited abstract in session TA-42: Quantum Computing for Continuous Optimization, stream Quantum Computing Optimization.

Tuesday, 8:30-10:00
Room: 98 (building: 306)

Authors (first author is the speaker)

1. Sander Gribling
Tilburg University

Abstract

We describe a quantum algorithm based on an interior point method for solving a linear program with n inequality constraints on d variables. The algorithm explicitly returns a feasible solution that is eps-close to optimal, and runs in time O(sqrt{n} poly(d,log(n),log(1/eps)) which is sublinear for tall linear programs (i.e., n >> d). Our algorithm speeds up the Newton step in the state-of-the-art interior point method of Lee and Sidford [FOCS '14]. This requires us to efficiently approximate the Hessian and gradient of the barrier function, and these are our main contributions.

To approximate the Hessian, we describe a quantum algorithm for the spectral approximation of A^T A for a tall n-by-d matrix A. The algorithm uses leverage score sampling in combination with Grover search, and returns a delta-approximation by making O(sqrt{nd}/delta) row queries to A. This generalizes an earlier quantum speedup for graph sparsification by Apers and de Wolf~[FOCS '20]. To approximate the gradient, we use a recent quantum algorithm for multivariate mean estimation by Cornelissen, Hamoudi and Jerbi [STOC '22]. While a naive implementation introduces a dependence on the condition number of the Hessian, we avoid this by pre-conditioning our random variable using our quantum algorithm for spectral approximation.

Keywords

Status: accepted


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