Quantum simulators with an exceptionally high number of controlled ‘qubits’ (the building blocks of a quantum computer, analogous to the bits in classical computers) are demonstrated in two separate experiments published in this week’s Nature. The systems can be used to study interactions that are not possible to model using classical computers.

Quantum simulators are a form of quantum computer that investigate (‘simulate’) how quantum particles interact, which in turn could aid the design of better quantum computers in the future. Small numbers of individually controlled qubits have already been used to simulate systems such as molecules. However, scaling this up to larger ensembles of quantum elements - and thus simulating more complex many-body quantum systems - has been a challenge.

Two independent studies demonstrate quantum simulators with a large number of controlled qubits. Mikhail Lukin and co-workers used 51 so-called Rydberg atoms and Christopher Monroe and colleagues 53 trapped ions to study phase transitions in Ising-type quantum magnets - a simplified ‘toy’ model of quantum interactions. Both groups observed and probed transitions of the particles into ordered states, providing insights into many-body interactions that cannot be described using classical approaches. The findings may provide a platform for studying quantum dynamics and quantum simulations in larger systems.