In 1925, a gentleman by the name of Werner Heisenberg turned the whole of physics on its head. It was then that he first formulated quantum mechanics, later expanded into quantum theory. The theory accurately describes the behaviour of light and matter at the level smaller than the atom, when classical physics – the Newtonian laws that describe the world at the scale we can see and feel – breaks down, giving way to a realm far more weird and wonderful. In quantum theory, the dynamics of light and matter can be characterised as probability amplitude waves of their possibilities. We can only know a limited amount about them: we can’t, for instance, know both a particle’s location and its momentum. And, perhaps strangest of all, the act of observing particles can fundamentally alter their nature.
Remarkably, all that weirdness gives rise to some exciting opportunities. In fact, these days, the ideas of quantum theory form the basis of most physics research. That’s not just true in research and technology directly related to quantum information; it also shapes fields including materials science, astronomy and cosmology, electronic engineering, mechanical engineering and even biology and AI.
That’s why, 100 years after quantum theory was formulated, the world is celebrating the International Year of Quantum Science and Technology. There’s particular cause for celebration at CUHK, which is in the vanguard of quantum science research, with the launch this year of the State Key Laboratory of Quantum Information Technologies and Materials. It focuses on all sorts of ways in which the deeply strange qualities described by quantum theory can be turned into technologies that are practically useful.
“In the past 100 years, the quantum revolution has changed our view of the world and powered our industry and economy with quantum-enabled technologies including semiconductor chips, lasers, atomic clocks and magnetic resonance imaging,” says Professor Liu Renbao, who leads the State Key Laboratory. “In the coming 100 years, we will witness the second quantum revolution unfolding, which will likewise change our view of the world, such as the basic structure of our spacetime, and lead to disruptive technologies.”
CUHK’s State Key Laboratory: at the forefront of quantum innovation
The laboratory is working on many of these technologies. They include diamond-based quantum sensing, which uses defects in diamonds to create devices that can detect everything from magnetic fields to pressure with incredible accuracy. There are also quantum interferometers, which exploit so-called quantum superposition, where a wave can exist on two paths simultaneously, again for ultra-precise measurement. The laboratory is also exploring quantum materials systems for quantum information processing, and developing of so-called integrated photonics devices, with applications in optical quantum computing, quantum communication and quantum sensing – the latter may yield real-life applications in less than 10 years, Professor Liu estimates.
“The establishment of the State Key Laboratory is not only a recognition of the strengths of Hong Kong – in particular CUHK – in quantum science research, but also provides local scientists with a platform to tackle major challenges in developing quantum information technologies,” says Professor Liu. “CUHK has a strong team in quantum research, especially in quantum sensing, topological quantum matter and integrated photonics. With these strengths and the recruitment of quantum talents, I am confident that CUHK can make significant contributions to quantum technologies and foundations, especially in discoveries of topological quantum states that will help to refresh our knowledge of the universe and matter and provide materials and methods for quantum computing and quantum AI.”
Professor Yang Chen-ning and his enduring legacy
CUHK and the rest of the world recently lost a scientific legend with the passing of Professor Yang Chen-ning – the first Chinese Nobel Laureate whose influence on quantum physics was incalculable. Professor Liu’s own work has involved so-called Lee-Yang zeros – a theory describing phase transitions between different states of matter that was introduced in 1952 by Professor Yang and his colleague Tsung-Dao Lee. This theory was first discovered to be deeply related to the superposition of a quantum sensor by a team led by Professor Liu in 2012. In 2015, the team achieved the first-ever experimental observation of Lee-Yang zeros. Professor Yang, as he recalls, expressed interest in such progress and invited him to discuss the relevant research.
“What deeply impressed me was not only his deep insight and agility but his true love for science – after the discussions, at the age of 90, he worked on a relatively small problem with detailed calculations, wrote up a manuscript by himself and published in a peer-reviewed journal. Such a work added very little to his scientific accomplishments. He enjoyed the work out of pure interest.”
Professor Yang was an enthusiastic science communicator, and this is a role that Professor Liu is also keen for the State Key Laboratory to assume. “I believe quantum literacy is necessary to modern citizens and there should be better ways to convey the ideas to school students and the general public. The Laboratory will put efforts into improving public quantum literacy by designing new courses and delivering public lectures.”
Looking ahead: the next quantum century
While the past 100 years of quantum development have been thrilling, the next 100, adds the professor, are set to be even more transformative.
“The next generation is the most important for developing quantum information science and technology. New concepts, new materials, new devices and new architectures are all needed to make programmable quantum computing true. The mission will take decades to achieve.”
In addition to such programmable quantum computing, he envisions that in the coming decades, quantum science will provide us with a better understanding of the structure of spacetime; and that it can be used to discover more about fundamental elements of the universe that we don’t currently understand, such as dark matter. In other words, powered by researchers such as those at the State Key Laboratory, quantum theory could one day become the key that unlocks everything.
