PhD student cracks high-dimensional quantum code
Isaac Nape from the University of the Witwatersrand is getting accolades from scientists in the field of quantum optics for a ground-breaking technique that holds untold promise.
Author:
9 March 2022
Popular depictions of scientists as either dark and twisted geniuses or wildly eccentric white men with a penchant for world domination have done little to advance the image of lab geeks everywhere. As the casual name-calling suggests, quantum scientists were thought of as socially inept and awkward to be around. We assumed they debated quantum mechanics for mains and probed photons for dessert like the cast of Big Bang Theory.
Movies and books sold us the idea that quantum mechanics was inaccessible to everyone but the oddballs whose genius shone through bad skin and an overactive metabolism. The idea of a quantum scientist being a balanced, softly spoken, young Black man with a love for music and a gift for dancing didn’t quite fit the script. Perhaps because not so long ago, if you grew up in a township west of Johannesburg, it was difficult to imagine being a quantum scientist – let alone one who devises a technique so significant it could change the trajectory of quantum optics for good.
Isaac Nape is a PhD student at the University of the Witwatersrand (Wits) and lead investigator in a crack team of quantum physicists who may have cut years off painstaking laboratory work. The team did this by revealing the hidden structures of quantum entangled states. If that sounds like a mouthful, it’s because it is – even in the enlightened field of quantum optics. It’s a study so important that it was published in renowned scientific journal Nature Communications in August last year.
In the field of quantum optics, this technique that Nape developed is now spoken of with astonishment for the tremendous amounts of time and effort it could save scientists experimenting in the field of quantum optics.
Nape and the team, which includes colleagues at Wits University Andrew Forbes, Jonathan Leach and his postdoctorate student Feng Zhu, developed a new approach to quantum measurement, testing it on a 100-dimensional quantum entangled state. To put that into perspective, using traditional methods to unravel a 100-dimensional state would take decades. With Nape’s new technique, information is gained in a matter of minutes, in essence asking an object: “Are you quantum or not?”
Quantum physics investigates matter and energy at its most fundamental level – one particle, respectively a photon or electron. Quantum optics studies the effects light has on photons.
“We devised a very simple technique that looks at the correlations between these two photons by projecting on specific patterns, which we structured in a specific way,” Nape said. “And with that technique we have reduced the number of measurements significantly.”
Seeing the light
It wasn’t the white lab coats or a freakish streak that lured Nape down this path of light. Quantum physics suited his inquisitive mind and a high threshold for concentration. Quantum mechanics has attracted the glitterati of scientists since the 1920s when German physicist Max Planck published a groundbreaking study on the effect of radiation on a “black body” substance. Planck showed that energy, in certain situations, can exhibit characteristics of physical matter.
“You really have to be sharp-minded and apply yourself. You kind of do physics like a philosopher. You have a nice question, or you observe something in nature, and then you start to build ideas around it,” Nape said. “Whether the answer is right or wrong, you always get something out. It’s that process that’s kind of interesting for me – the fact that I can come up with my own questions, or ask them and find answers.”
At 28, Nape has already made an indelible mark on the world of quantum optics. However, his path to a PhD at Wits University might have been an unlikely one had it not been for a few timely influences and chance conversations while growing up.
“Funnily enough, I wasn’t really the science geek in school. I was more the arts guy. I did a lot of dancing, I did a lot of cultural activities and it’s only after matric that I decided to jump into physics,” Nape said. “I was born in Pretoria and I moved around a lot. My family eventually settled in Randfontein and I went to Randfontein High.”
Related article:
It was the small talk with a “cool” high school teacher that introduced Nape to the world of quantum physics, but it took winning an astronomy quiz to pique his interest in science even further. “We managed to represent the school at district level, and then at provincial level. I met a lot of people and I think since then my teachers and my mom were trying to push me towards it.
“I kind of lost it when I got to high school, but then I had one cool teacher that I used to chat to a lot, my English teacher Ms Wendy Coen. We used to chat about a lot of fascinating things, and she was very smart. She also told me about quantum physics and stuff. There are these trails of influences,” he said.
After matric, Nape completed his undergraduate degree at the University of Pretoria before going on to do his honours. He then made a switch, doing his masters at Wits University under Forbes, who is also helping him complete his PhD.
Digging deeper
“During my undergrad, I was really fascinated with quantum mechanics. I think anyone who studies physics and encounters quantum mechanics and some of the interesting things that it suggests get trapped in. You get trapped in because you want to dig in and dig in and dig in,” Nape said. “I decided to choose something that’s a little bit applied but still allows me to play around with fundamental questions of nature. I chose to join Professor Andrew Forbes. We then just started to play with quantum mechanics using spatial patterns of light.
“So you have all these properties inside these light particles, and what you do is you manipulate them for either information processing or for sending communication signals. Now, the reason why we like using photons is because they are light. It’s the fastest object in the universe. Light is also quite easy to control. So I can observe all these fundamental properties of quantum mechanics with just simple lasers,” Nape explained.
Quantum technology holds the key to a world of superfast computing and more advanced cybersecurity. The faster transmission of information would also mean higher-quality imaging that can be used in medical scans.
“There are many different applications that are coming up. One main one is for encryption. Because quantum states have this nature that if you measure the disturber [meaning if someone tries to measure signals], you can actually detect it. And this sensitivity becomes larger and larger when you increase your alphabet. It becomes harder for someone to copy that information as well. That’s why we want to have these high-dimensional states and my technique makes it easy once you’ve measured them.”
Nape has set his sights on the international arena once he’s completed his PhD to try and get some international experience before returning home to give back.
“I think my supervisors worked quite hard to get the government involved to also fund a lot of quantum research. All those efforts will go nowhere if there aren’t people to carry on that kind of work,” Nape said. “So I think I see myself back here and then contributing to knowledge development, and maybe some new quantum technologies, because I think people are working towards getting quantum technology out of the lab and deployed in the industry. I want to see myself take part in the development of that field.”
Nape obtained his PhD from the University of the Witwatersrand on Friday 4 March.
