A small quantum computer that is reprogrammable - a property that has been difficult to implement - is reported in this week’s Nature. The device has the potential to be scaled up to build a bigger quantum computer, although this possibility has not yet been demonstrated.

Quantum computers can solve certain problems faster than conventional computers, but most of the systems demonstrated to date can only perform limited tasks and are difficult to reconfigure. A new computer constructed by Shantanu Debnath and colleagues is made up of just five bits of quantum information (qubits) and is shown to perform a number of different quantum algorithms. Some of these algorithms use quantum effects to perform a mathematical calculation in a single step, whereas a conventional computer would require several operations.

The qubits are stored in five trapped ions that can be manipulated with lasers and can be reconfigured without altering the hardware. This system can perform basic operations with an accuracy of around 98%, the authors report. They propose that more qubits could be added to the system, and multiple modules could be connected to increase the computational potential.