Using pairs of Cooper pairs to safeguard qubits inside a quantum computer from external noise has been created by a group of researchers from multiple France institutions. The team outlines how they approached the problem of qubit sensitivity to noise in a study published in the journal Physical Review X, as well as how well their strategy performed in tests.
External noise impacting qubits is a stumbling block in the development of quantum computers. Delocalizing the quantum information used in the computer is one of the most promising techniques to dealing with noise. This is due to the fact that the noise that causes issues is usually local. The goal is to decentralise data storage, and the researchers devised a new method for doing so.
Superconducting circuits are found inside quantum computers, and their states can be represented using Cooper pairs, which are pairs of electrons. The pairs tunnel through a Josephson junction in such systems. By altering the Josephson junction, the researchers created a novel type of superconducting qubit with nonlocalized quantum states. Two Cooper pairs were allowed to tunnel through at the same time in their configuration. A superconducting loop with superinductors was used to create the junction. The team was able to manage the kinetic interference co-tunneling element using this method. This prevented unwanted Cooper pairs from tunnelling, enabling those that were co-tunneling to pass through unscathed. The method increased the magnification of the superconducting phase by a factor of two.
The qubits’ sensitivity to noise was reduced by a factor of ten in the system. The researchers want to see if they can improve their system by adding a quantum phase-slip. This would reduce noise in both the phase and charge spaces, resulting in a significantly better level of protection.