Making a quantum computer powerful enough to tackle problems we cannot solve with current computers stays an enormous challenge for quantum physicists. A well-functioning quantum simulator — a selected form of quantum computer — could lead on to latest discoveries about how the world works on the smallest scales. Quantum scientist Natalia Chepiga from Delft University of Technology has developed a guide on the best way to upgrade these machines in order that they will simulate much more complex quantum systems. The study is now published in Physical Review Letters.
“Creating useful quantum computers and quantum simulators is one of the necessary and debated topics in quantum science today, with the potential to revolutionise society,” says researcher Natalia Chepiga. Quantum simulators are a form of quantum computer, Chepiga explains: “Quantum simulators are meant to handle open problems of quantum physics to further push our understanding of nature. Quantum computers can have wide applications in various areas of social life, for instance in funds, encryption and data storage.”
Steering wheel
“A key ingredient of a useful quantum simulator is a possibility to manage or manipulate it,” says Chepiga. “Imagine a automotive with out a steering wheel. It might probably only go forward but cannot turn. Is it useful? Provided that you’ll want to go in a single particular direction, otherwise the reply can be ‘no!’. If we wish to create a quantum computer that may find a way to find latest physics phenomena within the near-future, we’d like to construct a ‘steering wheel’ to tune into what seems interesting. In my paper I propose a protocol that creates a completely controllable quantum simulator.”
Recipe
The protocol is a recipe — a set of ingredients that a quantum simulator should should be tunable. In the traditional setup of a quantum simulator, rubidium (Rb) or cesium (Cs) atoms are targeted by a single laser. Consequently, these particles will take up electrons, and thereby develop into more energetic; they develop into excited. “I show that if we were to make use of two lasers with different frequencies or colors, thereby exciting these atoms to different states, we could tune the quantum simulators to many alternative settings,” Chepiga explains.
The protocol offers a further dimension of what may be simulated. “Imagine that you might have only seen a cube as a sketch on a flat piece of paper, but now you get an actual 3D cube that you may touch, rotate and explore in other ways,” Chepiga continues. “Theoretically we will add much more dimensions by bringing in additional lasers.”
Simulating many particles
“The collective behaviour of a quantum system with many particles is incredibly difficult to simulate,” Chepiga explains. “Beyond a couple of dozens of particles, modelling with our usual computer or a supercomputer has to depend on approximations.” When taking the interaction of more particles, temperature and motion into consideration, there are just too many calculations to perform for the pc.
Quantum simulators are composed of quantum particles, which suggests that the components are entangled. “Entanglement is a few type of mutual information that quantum particles share between themselves. It’s an intrinsic property of the simulator and subsequently allows to beat this computational bottleneck.”
