Take one atom of the element antimony, use an ion beam to shoot it into a silicon substrate, and you just may be on your way to building a working quantum computer.
That’s according to researchers at Sandia National Laboratories, who announced this week that they’ve used that technique with promising results.
In their experiment, described in the journal Applied Physics Letters, the researchers used an ion beam generator to insert the antimony atom into an industry-standard silicon substrate — a process that took just microseconds. That atom, equipped with five electrons, carries one more than a silicon atom does. Because electrons pair up, the odd antimony electron remains free.
That free electron is where the potential lies. The researchers subjected it to pressure from an electromagnetic field and monitored its “spin,” or whether it faced up or down. Spin is what enables electrons to serve as quantum bits, or “qubits,” which are the core components of quantum computing.
While traditional computers represent numbers as 0s or 1s, a qubit can simultaneously be a 0 and a 1 through a state known as superposition.
Now that they’ve precisely placed one donor atom in silicon, the researchers figure they can insert a second one at just the right distance for communication between them. That will essentially be the start of a quantum computing circuit.
Sandia plans to attempt that next feat later this year.
“Our method is promising because, since it reads the electron’s spin rather than its electrical charge, its information is not swallowed by background static and instead remains coherent for a relatively long time,” said postdoctoral fellow and lead researcher Meenakshi Singh.
The fact that the technique uses silicon is another advantage, since commercial fabrication technologies for silicon are already developed and it’s a lot cheaper than specialized superconducting materials.
While some parts of the experiment have been demonstrated before, this is the first time they’ve all worked together on a single chip and with each qubit precisely placed. Other approaches have taken more of a buckshot approach, meaning that researchers could only guess where each qubit was through a statistical approximation.
Thanks in part to the greater precision, the new technique may let manufacturers make more complicated multi-qubit structures than other methods could produce, the researchers said.