A step toward quantum computing

Mark Saffman and other physicists at the University of Wisconsin-Madison have taken an important step in creating a quantum computer.

As computer components continue to shrink, they approach atomic size. At that level, quantum mechanics is required to understand and manipulate those components. In the past, ions, or charged particles, have been trapped and used to run small computing programs. However, you need a certain number of quantum bits, or qubits, to get decent computing power. Ions, by their very nature, tend to interact with each other and with their environment. For this reason, it’s difficult to scale up the computing power when relying on ions.

In contrast, the University of Wisconsin physicists used two neutral (uncharged) rubidium atoms. They first trapped the atoms, and then used a laser to create a controlled-NOT (CNOT) gate between the atoms and to entangle the two atoms with each other. The CNOT gate is essential circuitry for quantum computers. Saffman’s team produced the first CNOT gate between neutral atoms.

Although this work was done with only two atoms, the scientists are hopeful that they will be able to scale up considerably. As a start, they are now working with 50 uncharged atoms to see if similar results can be achieved.

Meanwhile, researchers at the University of Paris also generated entanglement of two neutral rubidium atoms. They did not create a CNOT gate.