Two qubits in action, new step towards the quantum computer

Quantum computers have superior qualities in comparison to the type of computers currently in use. If they are realised, then quantum computers will be able to carry out tasks that are beyond the abilities of all normal computers.

A quantum computer is based on the amazing properties of quantum systems. In these a quantum bit, also known as a qubit, exists in two states at the same time and the information from two qubits is entangled in a way that has no equivalent whatsoever in the normal world.

It is highly likely that workable quantum computers will need to be produced using existing manufacturing techniques from the chip industry. Working on this basis, scientists at Delft University of Technology are currently studying two types of qubits: one type makes use of tiny superconducting rings, and the other makes use of ‘quantum dots’.

Now for the first time a ‘controlled-NOT’ calculation with two qubits has been realised with the superconducting rings. This is important because it allows any given quantum calculation to be realised. The result was achieved by the PhD student Jelle Plantenberg in the team led by Kees Harmans and Hans Mooij. The research took place within the FOM (Dutch Foundation for Fundamental Research on Matter) concentration group for Solid State Quantum Information Processing.