Tomorrow is Today

Major Quantum Computing Milestone: Physicists Build Single-Atom Quantum Bit in Silicon

Some of the popular approaches to building quantum computers include confining atoms in cryogenic gases to create quantum bits (or qubits) and using superconducting circuits.

In 1998, Bruce Kane, a physicist at the University of Maryland, in College Park, suggested an approach based on solid-state silicon semiconductors that are doped with phosphorus. He proposed using the quantum characteristic of spin in the nucleus of the phosphorus donor atom as the qubit.

Many scientists were enamored with this idea, because it showed the potential to integrate quantum computers with conventional silicon processing.

Morello and Dzurak were among the physicists impressed by Kane’s proposal, but they chose to investigate electron spins instead, because electron spins in silicon have very long coherence times—that is, it takes a relatively long time for such a qubit to lose its information.

In 2010, they demonstrated the ability to read the state of an electron’s spin. Basically, they managed to get the spin state of the electron to control the flow of electrons in a nearby circuit and produce a digital readout.

Now, Morello and Dzurak have discovered how to write the spin state. This completes the two-stage process required to operate a quantum bit. They managed to do this by using a microwave field to gain unprecedented control over an electron bound to a single phosphorous atom, which was implanted next to a specially designed silicon transistor.

(via Physicists Build First Single-Atom Quantum Bit in Silicon - IEEE Spectrum)