New Manufacturing technologies paving the way for Silicon or Solid-state quantum computing

Quantum bits, or qubits, are the basic building blocks of quantum computers, just as bits are that of modern computers. Researchers around the world have been exploring a range of different physical systems to act as qubits, including trapping and isolating ions by using electromagnetic fields, photons trapped in microwave cavities, nuclear spins, electron spins in quantum dots, superconducting loops and Josephson junctions, among others.

The idea of silicon quantum computing was first proposed in 1998 by Bruce Kane, a physicist at the University of Maryland, in College Park. Quantum computers based on familiar silicon could theoretically be manufactured in conjunction with the conventional semiconductor techniques found in today’s computer industry. A silicon approach to quantum computing also offers the advantage of strong stability and high coherence times for qubits. (High coherence times mean the qubits can continue holding their information for long enough to complete calculations.) Kane proposed using the quantum characteristic of spin in the nucleus of the phosphorus donor atom as the qubit.

Scientists and engineers from the Australian Research Council Centre of Excellence for Quantum Computation and Communication Technology (CQC2T), are developing a scalable quantum computer in silicon. They found that a single atom of phosphorus could be used to tightly hold an electron, which also carries a “spin” (like a tiny magnet) that could be used as a quantum bit. 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. Google’s Quantum AI Lab, have experimented with qubits based on superconducting metal circuits.