Scientists at the University of Wisconsin have designed a semiconductor-based device that can trap individual electrons and align them, bringing practical quantum computing one step closer to reality.

Developed by Profs. Mark Eriksson and Bob Joynt from Wisconsin's physics department, Max Lagally from materials science and engineering and Dan van der Weide from electrical and computer engineering, the device uses quantum dots to hold electrons.

One of the major hurdles to building a working quantum computer is gathering enough bits. In this design, each of the quantum dots contains one electron. When they are aligned, the electrons become usable quantum bits, or qubits.

Unlike bits in a traditional computer, which represent a "1" or "0", qubits can exist as both at the same time. This is why, in theory, quantum computers can calculate all the possible solutions to a problem simultaneously instead of one by one. This is also why the government is interested in quantum computing for its potential cryptography applications.

The device designed by the Wisconsin team uses layers of semiconductor materials and electrostatic forces to squeeze a single electron into place within each quantum dot. According to the design, a large number of dots are then aligned with their captured electrons separated by only one one-thousandth the width of a human hair.

Next up for the Wisconsin team is actually building the device, a process that has already begun.

Quantum computing is considered a type of holy grail for some researchers, while others have written the idea of a working quantum computer off as impossible. For now, while theories and designs abound, no one has built one.

A team made up of researchers from the University of Michigan, MIT and NIST proposed an architecture for a quantum computing in the June 13 issue of Nature. Their plan called for a quantum charge-coupled device (QCCD) consisting of a large number of interconnected atom traps. A combination of radiofrequency and quasistatic electric fields would be used to change the operating voltages of the traps, confining a few charged atoms in each trap or shuttling them from trap to trap, and the traps can be combined to form complex structures.

Ion trap technology is the only system that has shown in a lab to have all the ingredients necessary for quantum computing, but it's not clear whether the ion trap system is scalable in practice.