According to physicists at the University of Basel, there is a negative correlation between the spins of an entangled pair of electrons from a superconductor. The researchers used spin filters made of nanomagnets and quantum dots. They published their work in the journal Nature.
Two electrons can be entangled in their spins. In a superconductor, the electrons form Cooper pairs responsible for the lossless electrical currents in which individual spins are entangled.
The researchers have extracted electron pairs from a superconductor and spatially separated the two electrons using two quantum dots – nanoelectronic structures connected in parallel, each of which only allows single electrons to pass.
Researchers experimentally demonstrated that electrons from a superconductor always emerge in pairs with opposite spins. The physicists were able to measure that the spin of one electron points upwards when the other points downwards, and vice versa.
Using tiny magnets, they generated individually adjustable magnetic fields in each of the two quantum dots that separate the Cooper pair electrons. Spin also determines the magnetic moment of an electron, and only one type of spin is allowed through at a time. The research detected negative correlations between electron spins from a superconductor for the first time.
The research is considered an important step toward further experimental investigations of quantum mechanical phenomena, such as the entanglement of particles in solids, a key component of quantum computers.