Mining valuable insights from diamonds | MIT News
If Changhao Li traced the origins of his love of nature, he would point to the time when he was 9 years old, watching the night sky from his childhood home in the small town of Jinan, China. “At that moment I felt that nature is so beautiful, I just wanted to get out of Earth, go to the moon or even to Mars,” Li recalls.
That childhood dream sowed his love for physics, which he pursued in high school and high school, and finally at Xi’an Jiaotong University in China.
Li’s passion for the heavens has taken on a more microscopic and terrestrial form: it has translated into a love of quantum physics. He is a fifth-year doctoral candidate in the Department of Nuclear Science and Engineering (NSE) and is researching the science of quantum information, including quantum detection and computing, with Professor Paola Cappellaro.
The main thesis that drives the science of quantum information is that altering the state of a material at the subatomic level can have a significant impact on much larger scales. Quantum computing, for example, depends on the tiniest changes in the properties of the material to store and process more information than a simple classical binary mode could do.
The basic unit of information in quantum computing, equivalent to one bit in classical computers, is called the qubit. Exploiting defects in material structures is one way to make these qubits.
One aspect of Li’s research focuses on defects in very small diamonds, some of which are nanoscale. Experiments involve introducing an atomic-scale defect, known as nitrogen vacancy centers, into these diamonds, and subjecting the defects to extremely tiny perturbations, using microwaves or lasers, to create and control quantum states.
One of Li’s projects measures the fluorescence emitted by an altered diamond to give us more information about the external stimulus. Just as you would measure the temperature of an oven to measure its heat, measuring the fluorescence emitted by such a defective diamond can tell us what it is detecting and how much. For example, a sensor that could detect even a few hundred strands of the SARS-CoV-2 virus caused by Covid-19 is one of the applications Li is exploring with his colleagues.
In Physical review letters, Has published the conclusions of another research project that evaluates the symmetry of quantum systems. To explore the properties of quantum systems, we need to understand how quantum states behave over time, and their symmetries are important. “Engineering a system with the desired symmetry is a non-trivial task,” says Li. “Quantum properties are very unstable because they can interact with the environment. We need a very good shelf life for our qubits, and here we have developed a method to control and characterize this system.” Another research approach, the findings of which will be published soon, focuses on the simulation of a strain gauge field using diamond defects, which is related to fundamental science.
He tells her that understanding quantum information is primarily about studying basic science. “The basic principles of this world are beautiful and can explain many interesting phenomena,” he says. “This allows me to explore the universe, to understand how nature works,” Li adds.
The man who travels far knows more
His passion for understanding how nature works, whether on a star scale or a small quantum unit, has driven Li’s interest in physics since he was a child.
Her parents encouraged her love of physics, and a high school teacher taught her to think critically, to spot mistakes in her textbooks, and not to swallow information as truth. “You have to do simple experiments to find the truth for yourself,” was the lesson he learned from high school.
With that lesson safely stored, Li found high school a little more difficult and initially placed himself in the middle of the nearly 1,000 students. But the hard work and learning of others guided him to the top.
Placing the first in his class in both high school and high school, Li studied physics at Xi’an Jiaotong University, about 600 miles west of Beijing. It was his first time away from home and he found that his school needed a boost in subjects such as linear algebra. Once again, hard work paid off and Li graduated first in his class.
The university gave Li the opportunity to study in the United States during parts of his sophomore and third year of college. Through exchange programs, Li attended the University of Notre Dame for two months of summer research in 2015 and attended the University of California at Berkeley in 2016, his first year. The trips reinforced one of Li’s favorite quotes: “The man who travels far knows more.”
Notre Dame was the first time Li went abroad; he remembers trying to get used to burgers and fries, a radical departure from the traditional Chinese food he loves.
It was research at Berkeley – he fondly remembers the university library and dining halls – that cemented his love of quantum physics. When he returned to China, he knew he wanted to attend a graduate school and do research in the field. The MIT NSE was an opportunity to “work with the brightest people in the world,” says Li. Cappellaro is her inspiration: “She taught me to think about research, I’m very grateful,” she says.
He spends his free time re-learning Chinese cuisine (his parents help with tips) and playing mobile games like “Arena of Valor” with friends. Learning to play the guitar has been his pandemic hobby.
His fundamental love for nature, and for learning how things work, continues to inspire Li. “I focus on the smallest things and there is something really wonderful. It’s also about nature, right? If you learn how this little thing works, maybe you can also learn how the bigger things work, ”says Li.