Until now, scientists have thought that the process of erasing information requires energy (heat dissipation). But a new study by physicists Joan Vaccaro from Griffith University in Queensland, Australia and Stephen Barnett from the University of Strathclyde in Glasgow shows that, theoretically, information can be erased without using any energy at all.

Instead, the cost of erasure can be paid in terms of another conserved quantity, such as spin angular momentum.

Basically, instead of heat being exchanged between a qubit and thermal reservoir, discrete quanta of angular momentum are exchanged between a qubit and spin reservoir. The scientists described how repeated logic operations between the qubit’s spin and a secondary spin in the zero state eventually result in both spins reaching the logical zero state. Most importantly, the scientists showed that the cost of erasing the qubit’s memory is given in terms of the quantity defining the logic states, which in this case is spin angular momentum and not energy.