High-precision measurements have provided important clues about processes that impair the efficiency of superconductors. Future work building on this research could offer improvements in a range of superconductor devices, such quantum computers and sensitive particle detectors.
Superconductivity depends on the presence of electrons bound together in a Cooper pair. Two electrons become coupled because of interactions with the metal lattice, synchronizing with each other despite being hundreds of nanometres apart. Below a critical temperature, these Cooper pairs act as a fluid which doesn't dissipate energy, thus providing no resistance to electrical current.
But Cooper pairs sometimes break, dissipating into two quasiparticles – unpaired electrons – that hamper the performance of superconductors. Scientists still don't know why Cooper pairs break, but the presence of quasiparticles introduces noise into technologies based on superconductors.
'Even if there was only one quasiparticle per billion Cooper pairs, that would limit the performance of quantum bits and prevent a quantum computer from operating flawlessly,' says Elsa Mannila, who researched quasiparticles at Aalto University before moving to the VTT Technical Research Centre of Finland. 'If there are more unpaired particles, the lifetime of qubits is also shorter,' she adds.
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