Barrier relaxations of the classical and quantum optimal transport problems
Shmuel Friedland
TL;DR
The paper reframes both classical and quantum optimal transport in barrier-relaxation terms and applies interior-point methods to compute barrier-approximations of the primal and dual problems. By constructing self-concordant barrier functions (−log det for quantum, and log-based barriers for classical), it derives explicit optimality structures (e.g., rescaled exponential forms) and shows that the barrier problems admit efficient IPM-based solutions. It establishes rigorous complexity bounds across bipartite and multipartite settings, with classical BPOTP achieving $O(n^4\log(n^2 r/δ))$ iterations (and $O(n^4)$ per iteration) and quantum bipartite OT reaching $O(n^7\log n)$, plus scalable extensions to tensor-structured MPOTP and quantum MPOTP with bounds like $O(n^{3d/2}\log(n^d r/δ))$ and $O(n^{7d/2}\log(n^d r/δ))$ respectively. The framework provides a principled alternative to entropic/Sinkhorn relaxations, offering dual-trajectory advantages and broad applicability to high-dimensional OT problems in classical and quantum domains.
Abstract
In the last fifteen years a significant progress was achieved by considering an entropic relaxation of the classical multi-partite optimal transport problem (MPOTP). The entropic relaxation gives rise to the rescaling problem of a given tensor. This rescaling can be achieved fast with the Sinkhorn type algorithms. Recently, it was shown that a similar approach works for the quantum MPOTP. However, the analog of the rescaling Sinkhorn algorithm is much more complicated than in the classical MPOTP. In this paper we show that the interior point method (IPM) for the primary and dual problems of classical and quantum MPOTP problems can be considered as barrier relaxations of the optimal transport problems (OTP). It is well known that the dual of the OTP are advantageous as it has much less variables than the primary problem. The IPM for the dual problem of the classical MPOTP are not as fast as the Sinkhorn type algorithm. However, IPM method for the dual of the quantum MPOTP seems to work quite efficiently.
