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Interview: Malcolm R. Connolly, Cambridge

Hi Malcolm, what is your position at Cambridge and is it difficult for a scientist in the early stages of their career to handle all the demands of organizing a group?

I am currently an EPSRC early career research fellow setting up my lab at the Cavendish Laboratory in Cambridge. The fellowship is nice as it gives me a few years to develop independence and pursue some riskier ideas. It is definitely tricky getting the right balance between building momentum in and out of the lab while keeping a weather eye on where my career the rest of field is going long-term. Managing a team working on different approaches to a problem certainly keeps me on my toes!

What is your research focus right now?

The focus of my research is on understanding the quantum behavior of 2D materials such as graphene and topological insulators at low temperatures and seeing where we can exploit their properties in quantum devices such as qubits and single-electron pumps. A big part of what I do involves using low temperature scanning probe techniques to visualize quantum devices and get an early handle on how to exploit them in applications - for instance, my microscopy work on graphene nanostructures [Phys. Rev. B 83, 115441 (2011)] guided us in the development of a single-electron pump that has potential as a current standard in quantum metrology.

Where does your research fit in the big picture?

There is a big drive to use quantum effects such as superposition and entanglement in a wide range of applications, computing and sensing for example, but there is still lots to do. By pushing the boundaries with quantum materials and translating this to proof-of-concept devices I hope my research can open up new and unexpected avenues and approaches in future quantum technology. It is also exciting that we can develop bench/fridge-top tests of fundamental ideas in quantum physics using relatively simple solid-state devices. As for commercialization, when making quantum devices you nearly always end up finding solutions to similar problems faced by technology slightly closer to home, so we try to keep up to speed with the latest applications of 2D materials.

What is your most significant publication and why?

Probably my publication describing the high-frequency operation of a graphene single-electron pump [Nature Nanotechnology 8, 417 (2013)]. There is a lot of interest in pumps at the moment because in future they will probably be used as a current standard, leading to a redefinition of the Ampere in terms of the fundamental charge on the electron. Unlike GaAs and Si the band structure of graphene is not really suited for confining single electrons, but this paper showed that it nonetheless works at much higher frequency than was achieved in previous metallic pumps.

You have Zurich Instruments UHFLI for some time now in your lab - how does it fit in with your work?

We do quite a bit of radiofrequency engineering to allow us to manipulate and probe quantum devices on short timescales. For instance, demodulating the signal reflected from an RF tank circuit coupled to a graphene quantum dot allows us to measure single electron tunneling and relaxation events. Here the UHFLI fits in nicely as the 600 MHz input bandwidth is compatible with our typical RF tank circuits and the demodulator bandwidth of 5 MHz allows us to monitor fast processes. I like the fact we can do basic tests on new RF circuits quickly at room temperature as well as get creative with actual experiments at low temperatures, for instance by using frequency multiplexing and multiple demodulators to probe different parts of the device, or using the boxcar option to perform pulsed measurements.

Thanks a lot Malcolm. One last question. You said earlier your partner is Italian, what is your favorite Italian dish?

Pizza happens to be one of my favourites full stop actually. She will testify that I am constantly searching for the perfect one!

Malcolm R. Connolly

Malcolm R. Connolly is an EPSRC Early Career Research Fellow in the Semiconductor Physics Group at Cambridge University.

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