Physicists Employ Berry’s Phase to Control Quantum Interference

By G.P. ThomasJul 6 2012

Researchers from the Centre for Quantum Photonics (CQP) at the University of Bristol have shown that quantum interference between photons can be fine-tuned by employing Berry’s phase.

The study offers a method to devise robust circuits for the next generation of photon-based quantum simulators. These simulators are devices of photons developed for simulating other quantum devices and are envisaged to be physically implemented ahead of the quantum computer. The study is a marriage of two significant developments at Bristol, namely, the geometric phase effect formulated by Professor Sir Michael Berry at the School of Physics and the current research initiatives in quantum technologies undertaken at CQP.

In 1984, Professor Berry described an effect exhibited in quantum particles where a quantum particle reverting to its starting point at the end of a cyclic expedition is found to undergo a slight change by way of a phase shift. This effect is the subject of numerous studies attempting to identify reliable techniques to realize a universal quantum computer. In another significant development in 1987, Hong Ou and Mandel (HOM) experimentally showed the unusual interference between two photons where they exhibited a tendency to be bound together. This quantum interference effect is the foundation for photonic quantum simulators whose nature makes it difficult to be employed in current generation computers. The team at Bristol combined the two effects to demonstrate the fine-tuning of HOM using Berry’s phase. The study could pave the way for photonic quantum simulator circuits with fault tolerance.