Simulations are an important tool on the path to realizing quantum computers. With the help of special programs called emulators, quantum systems are mimicked on supercomputers or, in a slimmed-down form, on conventional computers. Researchers at the Jülich Supercomputing Centre are developing models and methods for this.
The advantages: all simulated qubits work one hundred percent reliably – in contrast to real qubits, where errors often occur. Comparing simulation and reality allows the computational quality of a quantum computer to be assessed. In addition, algorithms that will be run on quantum computers in the future can be developed and tested.
However, simulations are also used to investigate the properties of potential quantum materials – for example, the performance of Majorana qubits, a possible future qubit type that is less prone to errors than semiconductor and superconducting qubits.
Quantum computer from the OpenSuperQ project.
World record for simulated qubits
Jülich’s emulator for quantum computers is known as the Jülich Universal Quantum Computer Simulator (JUQCS). With 48 qubits, it holds the world record for the highest number of simulated qubits. To achieve this, Jülich scientists used the Sunway TaihuLight (China) and K (Japan) supercomputers.
However, simulating more than 48 entangled qubits is considered difficult, as every additional qubit doubles the memory requirement of the computer on which the simulation is running. Even state-of-the-art supercomputers reach their limits at this point.
Simulations on Jülich’s supercomputer JUWELS also contributed to Google’s demonstration of quantum supremacy in 2019. The term describes the point from which a quantum computer outperforms conventional computers in a particular task for the first time. Proving this had been considered a major challenge. The simulations on JUWELS helped verify the results and determine the performance of Google’s quantum processor.
Simulation of quantum materials
The Simulation and Data Laboratory Quantum Materials at the Jülich Supercomputing Centre offers scientists the opportunity to carry out simulations in the field of quantum materials as well as calculations of the quantum mechanical properties of materials. For this purpose, the laboratory develops and optimizes mathematical models and tools.