Building a quantum computer powerful enough to tackle problems that we cannot solve with existing computers remains a major challenge for quantum physicists. A well-functioning quantum simulator — a specific type of quantum computer — could lead to new discoveries about how the world works on a small scale. Quantum scientist Natalya Chepiga from Delft University of Technology has produced a guide on how to upgrade these machines so that they can simulate even more complex quantum systems. The study is now published. Physical examination letters.

“Building useful quantum computers and quantum simulators is one of the most important and hotly debated topics in quantum science today, with the potential to revolutionize society,” says researcher Natalia Chepiga. A quantum simulator is a type of quantum computer, Chepega explains: “Quantum simulators aim to solve open problems in quantum physics to further our understanding of nature. Quantum computers are widely used in various areas of social life. Applications will be, for example, finance, encryption and data storage.”

Steering wheel

“A key component of a useful A quantum simulator is a possibility to control or manipulate it,” says Chepega. “Imagine a car without a steering wheel. It can only move forward but cannot turn. Is it useful? Only if you need to go in a certain direction, otherwise the answer will be ‘No!’ If we want to build a quantum computer capable of discovering new physics phenomena in the near future, we need to build a ‘steering wheel’ that looks interesting. In my paper I propose a protocol that creates a fully controllable quantum simulator.”


A protocol is a recipe — a set of components that a quantum simulator must be able to tune. In the traditional setup of a quantum simulator, rubidium (Rb) or cesium (Cs) atoms are targeted by a single laser. As a result, these particles will take on electrons, and thus become more energetic. They get excited. “I show that if we use two lasers with different frequencies or colors, thereby exciting these atoms to different states, we can tune the quantum simulators to many different settings,” Chepega said. Tells.

Protocols offer an additional dimension to what can be simulated. “Imagine you’ve only seen a cube as a sketch on a flat piece of paper, but now you’ve got a real 3D cube that you can touch, rotate and explore in different ways, Chepega continues. “Theoretically we could add more dimensions by bringing in more lasers.”

Simulation of many particles

“The collective behavior of a quantum system with many particles is extremely difficult to simulate,” Chepega explains. “Beyond a few dozen particles, modeling with our normal computer or supercomputer has to rely on approximations.” Considering the interaction of more particles, temperature and motion, the computer has to do a lot of calculations.

Quantum simulators consist of quantum particles, which means the components are entangled. “Entanglement is the kind of mutual information that quantum particles share with each other. It is an intrinsic property of the simulator and therefore allows this computational bottleneck to be overcome.”