On the path to building a quantum computer

On a quiet morning at the Research Advancement Centre building, a steady hum and chirp drifts down the hallway.

The repetitive, calming whir signals the ongoing, crucial work of the dilution refrigerator keeping the tiny device inside cooled and in the desired quantum state.

Principal investigator JONATHAN BAUGH walks the hall to the dilution refrigerator in the Coherent Spintronics lab daily. There, he and his students experiment with nanoscale electronic devices at low temperatures to learn more about quantum physics. According to Baugh, “Understanding more about how to control physics at the nanoscale gives us a powerful toolbox to work with.”

It’s a toolbox that Baugh’s been developing for 15 years. He started his journey at the Institute for Quantum Computing (IQC) as one of the very first postdoctoral fellows in 2002. His supervisor, RAYMOND LAFLAMME, introduced him to the field of quantum information. Now Baugh’s research group focuses on applying quantum control methods to single quantum systems with potential to scale up, like the spin of a single electron trapped in a quantum dot (also known as an artificial atom). The quantum dots studied in Baugh’s lab are made from semiconductors and are around 50 nanometers in size.

Control at scale

Gaining the ability to control quantum states at the level of one or two electrons is the first step in a larger, more ambitious endeavour. The ultimate goal is to put the pieces in place to build a large scale quantum information-processing device – the inner workings of a quantum computer. “That would have a huge impact and could change the world,” said Baugh. “Theoretically we can model the behaviour of these quantum systems. Until we actually make and study them in a lab, we won’t know what all the real challenges to scaling up will be.”

A glimpse into the future

Experimental research in the lab doesn’t always lead to quick results. But it does give us a glimpse into future applications For quantum technologies. “Sometimes there are big breakthroughs, but equally important are the incremental steps in getting to the final goal,” said Baugh.

One example is the quantum memristor – a resistor with memory – the result of Baugh’s collaboration with colleagues at Oxford University. The quantum memristor regulates the flow of electrical current using a pair of quantum dots. Neuroscientists predict that memristive-type components could be important for the study of brain function. In concept, the quantum memristor may be used to build artificial circuits to simulate the way the brain works.

In the lab, the constant hum and chirp of the dilution refrigerator is a reminder of steady steps forward. Advancing technology is catching up with theory, like the nanoscale devices in Baugh’s lab. The path to building a quantum computer is in sight.