An ordinary laptop has for the first time "caught up" with a quantum computer: Complex problem solved

Scientists from the Center for Computational Quantum Physics at the Flatiron Institute in New York have refuted a claim made by D-Wave. The task of simulating the dynamics of hundreds of entangled qubits, which the quantum computer supposedly could not solve using any classical method, was successfully performed on an ordinary laptop.

How it was done

The main tool was tensor networks — a mathematical structure that efficiently compresses the wave function of a quantum system, much like a zip archive compresses data. The wave function of hundreds of interacting qubits grows exponentially and cannot be directly stored in an ordinary computer's memory. Tensor networks represent the system as a set of interconnected tables of numbers, making the calculations feasible.

Lead author Joseph Tindall conducted the initial calculations on his personal laptop using the ITensor library. Despite the modest hardware, the results matched theoretical predictions and data from the quantum computer.

A key role was played by the belief propagation algorithm, developed in the 1980s for artificial intelligence problems and adapted for three-dimensional quantum systems.

Why this matters

The discovery shows that classical and quantum computing are not in competition but rather complement each other. Classical simulations help understand the limits of quantum machines, while progress in quantum hardware stimulates the development of new algorithms for conventional computers.

The researchers' next goal is problems with mobile electrons that directly describe real quantum materials.

In brief

Scientists at the Flatiron Institute solved on an ordinary laptop a problem of modeling the dynamics of hundreds of entangled qubits that D-Wave claimed was impossible for classical computers. The key tools were tensor networks and the belief propagation algorithm. This demonstrates that classical methods continue to evolve and can compete with quantum methods in certain tasks. The work was published in the journal Science.