Record-setting hybrid atom array could power quantum computer RAM and CPU
Researchers at the University of Chicago have demonstrated a key technology that could help scale up quantum computers, and used it to create a model with a record-breaking 512 qubits. The team combined atoms of two elements into an array, so that one type of atoms can be manipulated at a time without disturbing its neighbors.
Quantum computers are devices that perform calculations and store information by taking advantage of the bizarre realm of quantum physics, including phenomena like superposition and entanglement. Armed with this, quantum computers are poised to outperform traditional computers by several orders of magnitude, but their instability makes them difficult to scale up.
One of the most promising quantum computer structures is made up of an array of atoms serving as qubits, each held in place with laser beams. Normally the atoms in these arrays are all the same element, which allows them to be entangled together in a big group. The problem is that this makes it hard to manipulate any individual atoms without also disturbing their neighbors, meaning that measuring the data can ruin the whole system.
For the new study, the researchers experimented with creating an array of atoms of two different elements, rubidium and cesium. By placing the two in an alternating pattern, each atom can be surrounded by atoms of the other element, meaning that any given qubit could be measured with minimal interruption to its neighbors.
The team says this technique has a range of advantages. Because each of the elements can be controlled independently, one kind of atom could be used as memory while the other performs calculations, making them somewhat analogous to RAM and CPU. Or it could reduce downtime as quantum computers are reset.
“When you do these experiments with the single atoms, at some point, you lose the atoms,” said Hannes Bernien, lead researcher on the study. “And then you always have to re-initialize your system by first making a new, cold cloud of atoms and waiting for individual ones to get trapped by the lasers again. But because of this hybrid design, we can do experiments with these species separately. We can be doing an experiment with atoms of one element, while we refresh the other atoms, and then switch so we always have qubits available.”
In tests so far, the team demonstrated an array with an impressive scope – 256 cesium and 256 rubidium atoms. With a total of 512 atoms, that makes this the largest array of qubits assembled so far, surpassing IBM’s Eagle processor with 127 qubits.
The difference though is that the Eagle is a commercially available processor, whereas the new hybrid array is still just a prototype, and doesn’t have all the necessary components to be called a quantum computer yet. But the team says the technique demonstrated could be useful in building more powerful and stable quantum computers.
The research was published in the journal Physical Review X.