The coherent simulation of a quantum phase transition in a programmable 2,000 qubit Ising chain

Ingrid Fadelli is a writer for the website Phys.org.

Many challenges need to be overcome before quantum computers can compete with classical computers. Physicists and computer scientists are trying to estimate the quantum computing capabilities that will show up in the future.

The usefulness of quantum simulations for determining the near-term potential of quantum computers has been proven. One approach that can be explored using quantum simulations is quantum annealing.

A group of researchers in Canada, the U.S. and Japan have recently done a quantum phase transition simulation. Their results were presented in a paper.

According to Andrew D. King, one of the researchers who carried out the study, chronic annealing has been something they wanted to showcase for a long time. It allows us to compare the behavior of our quantum system with ideal Schrdinger dynamics and provide both strong evidence of quantum-ness and a benchmark of this quantum-ness. The 1D chain is perfect for this because it has a well-known closed-form solution which means that we can solve it classically without a lot of simulation.

A group at Harvard University has done simulations of the 1D Ising chain. The simulation carried out by King and his colleagues is the first of its kind. The larger and more strongly correlated states were realized by the researchers.

The main variable in our experiment is the time the D-Wave processor takes to go from its initial quantum superposition state to the classical endpoint of computation. The speed limit is placed on the system to allow for tolerances. We went 100 times quicker than this.

King and his colleagues had to apply more stringent hardware requirements due to the higher speeds of their system. They were able to perfectly sync the thousands of qubits.

The researchers used a processor created by D- Wave Systems. They chose to test its effectiveness with a simple and well understood quantum phase transition.

The ideal quantum model with no environmental effects is a new development in the field of quantum annealing. The system is manifestly quantum and we can program more complex systems into the quantum annealer and expect it to follow the true quantum dynamics of the Schrdinger equation.

The simulations were in line with predictions of quantum theory. New and exciting possibilities for the study of quantum phase transitions could be opened by their work. In their next works, King and his colleagues would like to use more exotic quantum phase transitions, which can't be mimicked using classical computers.

King said that most people want to use quantum annealing for simulation or for Optimization. The textbook quantum phase transition that we studied in this work is only applicable to Optimization so it's important to tie these two areas together. It's known that quantum annealers can solve problems very quickly. The next job will be to explain the role of quantum critical dynamics in quantum annealing maximization.

More information: Andrew D. King et al, Coherent quantum annealing in a programmable 2,000 qubit Ising chain, Nature Physics (2022). DOI: 10.1038/s41567-022-01741-6

Jacek Dziarmaga wrote a paper on Dynamics of a Quantum Phase Transition.

The Quantum Kibble–Zurek mechanism and critical dynamics are discussed in Nature.

Journal information: Nature , Nature Physics , Physical Review Letters

There is a science network.