Paul van Gerven
18 November 2019

A team from the Vrije Universiteit Brussel (VUB) succeeded in constructing a so-called coherent Ising machine (CIM) from off-the-shelf optical components. This resulted in a drastic size reduction: whereas an entire laboratory is needed to house a typical CIM, the Brussels device is about the size of an Internet router.

A CIM specializes in solving combinatorial optimization problems, such as that of the infamous traveling salesman. Drawing upon a century-old approach to explain the rise of magnetism from spin interactions between atoms, problems are represented by interacting computational ‘magnets’, which are either in an ‘up’ or a ‘down’ state. Just like atomic spins, through a complex interplay of interactions, eventually settle into the lowest energy configuration, the computational elements settle on an optimal configuration – which represents the solution.

CIM principle
Credit: Nature Communications

CIMs are theoretically 100 times faster at solving combinatorial optimization problems than ordinary computers. “However, in their current form, these machines are still too far removed from commercial applications,” VUB researcher Fabian Böhm explains. “Because they use miles of optical fibers and high-powered laser systems, they are simply too complex, too expensive and too large. The new design developed by our team at VUB makes them small and cheap enough to replace digital computers.”