Daria Jelonek

Libby Heaney

Engineer and member of the Centre of Quantum Photonics at the University of Bristol, Eric Johnston, gave a quantum computing lecture to Information Experience Design students and staff today at the the Royal College of Art.  This was the first time some of the students had heard from a scientist working in the field of quantum computing and acted as a primer to these emerging technologies.

Throughout his talk entitled ‘Engineers view of Quantum Computation’, EJ spoke about the practicalities of quantum computing on integrated photonic chips. Some aspects of the talk can be found in this Vimeo video.

EJ started by giving us an overview of the chips; spoke about how the qubits were encoded via a single photon spread between two different spatial pathways; explained how photons are sent on and off the chips and explained how the different quantum gates (single qubit and entangling) were implemented.

Furthermore, we heard about how the distinguishability (or rather indistinguishability) of photons, the fact that two photons in the same set of quantum states (i.e. identical in polarisation, space and time) determines which quantum gates can be applied and which outputs can be detected.

He mentioned that running the chips was relatively straight forward, but due to its cost, finding time to use the detector to measure the final output of the computation was the limiting factor in running most experiments in their lab.

To support the lab work, EJ has developed a useful simulation tool that visualizes the amplitude and phases of complex pure quantum states at different stages of the quantum computation.  Directly observing these quantum states before the end of the quantum computation would collapse the quantum state and destroy the coherences, hence EJ’s simulator provides a peak inside the black box.

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Photos: Daria Jelonek