Penn State researchers discover fresh way to speed up creation of quantum computers

Via the entropy of a 3D lattice of super-cooled, laser-trapped atoms

A team of researchers at Penn State University have discovered a way to speed progress toward creating quantum computers.

The process, the scientists say, can be done via reduced entropy (the degree of disorder or randomness) of a three-dimensional lattice of super-cooled, laser-trapped atoms.

This involves rearranging a randomly distributed array of atoms into neatly organised blocks, and performing the function of what is referred to as "Maxwell's demon". This is the thought experiment from the 1870s that challenged the second law of thermodynamics.

These organised blocks of atoms could form the basis for a quantum computer that uses uncharged atoms to encode data and perform calculations, the researchers claim.

"Traditional computers use transistors to encode data as bits that can be in one of two states: zero or one," said David Weiss, professor of physics at Penn State and the leader of the research team.

"We are devising quantum computers that use atoms as ‘quantum bits' or ‘qubits' that can encode data based on quantum mechanical phenomena that allow them to be in multiple states simultaneously. Organising the atoms into a packed 3D grid allows us to fit a lot of atoms into a small area and makes computation easier and more efficient."

The researchers used lasers to trap and cool atoms in a three-dimensional lattice with 125 positions arranged as a 5 by 5 by 5 cube.

They then randomly fill about half of the positions in the lattice with atoms. By adjusting the polarisation of the laser traps, the researchers moved atoms individually or in groups, reorganising the randomly distributed atoms to fully fill either 5 by 5 by 2 or 4 by 4 by 3 subsets of the lattice.

"Because the atoms are cooled to almost as low a temperature as possible, the entropy of the system is almost entirely defined by the random configuration of the atoms within the lattice," said Weiss.

"In systems where the atoms are not super-cooled, the vibration of the atoms makes up the majority of the system's entropy.

"In such a system, organising the atoms does little to change the entropy, but in our experiment, we show that organising the atoms lowers the entropy within the system by a factor of about 2.4."