In Brief

10 August 2016

Quantum computing race heats up as trapped ions rival microchips

IN THE race to build larger quantum computers, two contrasting strategies have drawn neck and neck. Both sides can now create simple devices that run multiple types of quantum software.

In May, IBM made a quantum computer available for anyone to use over the internet. It uses five quantum bits, or qubits, so can only handle relatively small problems – but it’s programmable just like a PC.

IBM uses superconducting qubits built using techniques from the conventional computer chip industry.

Now, a team at the University of Maryland in College Park has made a programmable five-qubit computer using a different approach (Nature,


These qubits are made from ytterbium ions held in place by magnetic fields and lasers. “Ions are nature’s quantum units,” says team member Shantanu Debnath. “If you have a bunch of them in a processor, all of them are identical, and that is a significant advantage.”

Trapped-ion qubits have another edge over the superconducting variety in being able to communicate with each other at a distance, thanks to the weird property of quantum entanglement. This lets them process data more easily.

In contrast, superconducting qubits can swap data only with their nearest neighbour, meaning two distant qubits have to slog through all those in between to communicate. “That is something they are going to pay for in the long term,” says Debnath.

This article appeared in print under the headline “Quantum computing rivals go head to head”