A research team at the Laboratoire de Physique de l’Ecole Normale Supérieure (LPENS) in France has developed a new way to protect superconducting quantum bits (qubits) from noise. Thanks to a novel superconducting circuit element that effectively “spreads out” the qubit’s quantum state, the team reduced the qubit’s sensitivity to an external magnetic flux by a factor of 10. This improvement could lead to the development of next-generation superconducting qubits that are less prone to errors.
Quantum information stored in qubits is fragile to noise from the surrounding environment, and this remains a major challenge for building large-scale quantum computers. One prominent approach to protecting qubits from noise is to delocalize their quantum information: because noise is typically local, quantum information that is stored non-locally is less likely to be spoiled. For example, certain types of quantum error correction encode information in a network of many spatially separated qubits.
Interestingly, this delocalization approach can also be applied to a more abstract form of space known as the Hilbert space of a qubit. One popular example is the superconducting transmon qubit, the states of which are greatly spread over many charge values, providing some immunity against charge noise.