A team of Australian engineers is claiming it has made the first working quantum bit (qubit) fashioned out of a single phosphorous atom, embedded on a conventional silicon chip.

This breakthrough stems all the way back to 1998, when Bruce Kane — then a University of New South Wales (UNSW) professor — published a research paper on the possibility of phosphorous atoms, suspended in ultra-pure silicon, being used as qubits. For 14 years, UNSW has been working on the approach — and today, it has finally turned theory into practice.

To create this quantum computer chip, the Australian engineers created a silicon transistor so small that “electrons have to travel along it one after the other.” A single phosphorous atom is then implanted into the silicon substrate, right next to the transistor. The transistor only allows electricity to flow through it if one electron from the phosphorus atom jumps to an “island” in the middle of the transistor. This is the key point: by controlling the phosphorus’s electrons, the engineers can control the flow of electricity across the transistor.

At this point, I would strongly recommend that you watch this excellent video that walks you through UNSW’s landmark discovery — but if you can’t watch it, just carry on reading.



To control the phosphorus atom’s electrons, you must change their spin, which in this case is done by a small burst of microwave radiation. In essence, when the phosphorus atom is in its base state, the transistor is off; it has a value of 0 — but when a small burst of radiation is applied, the electrons change orientation, one of them pops into the transistor, it turns on; it has a value of 1. For more on electron spin and how it might impact computing, read our spintronics and straintronics explainer.

Now, we’ve written about quantum computers before — the University of Southern California has created a quantum computer inside a diamond, for example — but the key breakthrough here is that UNSW’s quantum transistor has been fashioned using conventional silicon processes. Rather than beating its own path, UNSW is effectively riding on the back of 60 years and trillions of dollars of silicon-based electronics R&D, which makes this a much more exciting prospect than usual. It is now quite reasonable to believe that there will be readily available, commercial quantum computers in the next few years.

Now read: New quantum teleportation record paves the way towards a worldwide quantum network

Research paper: “A single-atom electron spin qubit in silicon” doi:10.1038/nature11449