Take your partners
1 min read
Physicists at the US National Institute of Standards and Technology (NIST) have induced thousands of atoms trapped by laser beams to swap ‘spins’ with partners simultaneously. The repeated exchanges, like a quantum version of a square dance, may allow logic operations to be carried out in quantum computers.
The NIST experiments demonstrated the essential part of a so called swap operation, in which atom partners exchange their internal spin states, trading an ‘up’ spin (notionally a binary 1) for a ‘down’ spin (binary 0.) Unlike classical bits, which would either swap or not, quantum bits can be simultaneously in an unusual state of having swapped and not swapped at the same time. Under these conditions, spin swapping has the effect of ‘entangling’ the pairs; a quantum phenomenon that links the atoms’ properties, even when they are physically separated. The swapping process is a way of creating logical connections among data.
The NIST experiment was performed with about 60,000 rubidium atoms trapped within a 3d grid of light formed by three pairs of infrared laser beams arranged to create two horizontal lattices. This created many pairs of energy ‘wells’ for trapping atoms.
The scientists attempted to place an atom in each well, each pair with opposite spins. They then merged the paired wells to force each pair of atoms to interact with each other. Due to the rules of quantum mechanics, the merged atoms oscillate between the condition in which one atom is 1 and the other is 0, to the opposite condition. As they swap spins, the atoms pass in and out of entanglement. NIST believes this to be the first time that quantum mechanical symmetry has been used to perform such an entangling operation with atoms.
