NIST brings quantum computers closer

Mechanical Engineering, Jun 2003 by Thilmany, Jean

Scientists at the National Institute of Standards and Technology in Gaithersburg, Md., say they've developed a way to increase control of the quantum bits, or qubits, that may some day store and process data using the principles of quantum mechanics.

Qubits represent information as ones and zeros as digital bits do in today's computers. The NIST team demonstrated a way to precisely control a computational operation, which they call a logic gate. They can control the operation between two qubits 97 percent of the time, compared to just 80 percent with previous techniques. With further improvements in logic gate reliability, universal computation on a large scale should be possible, the scientists say.

The scientists used ions, or charged atoms, as qubits, for their experiment. To increase control of quantum bits, the NIST scientists used lasers to manipulate beryllium ions trapped in a vacuum; they spin up or down to represent one or zero. The quirks of quantum mechanics allow ions to exist in blends of the two spin states and also to become entangled so that the properties of two ions are intertwined. Qubits, therefore, are able to represent multiple values simultaneously and to link values in logical ways.

It is the qubits' capability to be intertwined that would allow a quantum computer to perform tasks like factoring very large numbers that are impossible with today's technology. The NIST experiments focused on manipulating qubits to control their entanglement and thus the computation process.