Diamond quantum information processing
Through improving the interaction between individual computing units, Lau hopes to harness the power of quantum resources to “fuel a computer or communication device”.
When his grandmother became ill in 2009, Lau had been pursuing the study of gravitational waves. Lau had a sudden realisation that, although his studies could provide some benefit to the human race in the long term, they would not have a direct impact on the people around him, such as the medical staff caring for his grandmother.
Lau believes that there are two ambitions for physicists: to understand more about the world, and to benefit others. He feels that both are important, and so is choosing a path that can satisfy both ambitions.
With this realisation, Lau made the decision to move to an area of physics that he believes is practical enough to contribute more immediately to mankind. Today, he is a postdoctoral researcher at the Institute of Theoretical Physics at Ulm University in Germany, working under the supervision of Professor Martin Plenio.
According to Lau, the main challenge of the current diamond quantum system is that the individual computing units, also known as NV centres, interact weakly with each other. This suppresses the environmental distortion on the centres that leads to an improvement of the storage time of quantum information, but also increases the difficulty of powerful large scale quantum computing, which requires the NV centres to operate collectively.
A common method to impose long-range interaction between NV centres is to use a quantum bus that can spread quantum correlation over a long distance. This could be implemented by, for example, implanting a chain or spin, or coupling the NV centres to a common mechanical oscillator. Implanting a spin chain is technically challenging as the position of the spins cannot be precisely controlled, Lau says, therefore the mechanical oscillator approach may seem more promising.
While the conventional way to couple with mechanical oscillators is through the intrinsic electric field sensitivity of NV centres, this coupling can be weak because the electric field sensitivity is weak. On the other hand, NV centres are more sensitive to magnetic fields, Lau says. “Our goal is to devise a hybrid quantum device that could harness magnetic field sensitivity to increase NV-oscillator coupling”.
Lau believes that diamonds could be an alternative to trap ions, which he worked on during his PhD at the University of Toronto. “There are limitations to trap ions such as size”, he says, “they cannot make a very large trap ion quantum computer, so I think we will have to move to other approaches”.
In his time at the University of Toronto, Lau wrote on the “Insecurity of position-based quantum-cryptography protocols against entanglement attacks”, and “Proposal for a scalable universal bosonic simulator using individually trapped ions” amongst others.
Our goal is to devise a hybrid quantum device that could harness magnetic field sensitivity to increase NV-oscillator coupling
Looking towards the future, Lau hopes to become an educator one day, either teaching as a professor in a university while continuing his research, or to impart his knowledge on high school students in Hong Kong. “I would not say I have done big things, but I have done some interesting things,” he says.
As we close our conversation, Lau ponders, “If I die, what do I leave behind? If I am a businessman, I may leave behind money but that’s not very important to me. Scientific contribution will be more long-lasting than money.”
Dr Kero Lau completed his bachelor’s and master’s degrees in physics at the Chinese University in Hong Kong in 2009. He then went on to pursue quantum optics and quantum information at the University of Toronto. Lau received a Croucher Fellowship in October 2014 to pursue his postdoctoral research at Ulm University.
To view Kero Lau’s personal Croucher profile, please click here.