Quantum Interference as a function of Berry's phase

M. J. Rave

Anthony Laing, Thomas Lawson, Enrique Martín López +1 more

Emerging models of quantum computation driven by multiphoton quantum interference, while not universal, may offer an exponential advantage over classical computers for certain problems. Implementing these circuits via geometric phase gates could mitigate requirements for error correction to achieve fault tolerance while retaining their relative physical simplicity. We report an experiment in which a geometric phase is embedded in an optical network with no closed loops, enabling quantum interference between two photons as a function of the phase.

Xiao-Xiao Zhang, Naoto Nagaosa

The Berry phase effect plays a central role in many mesoscale condensed matter and quantum chemical systems that are naturally under the environmental influence of dissipation. We propose and microscopically derive a prototypical quantum coherent tunneling model around a monopole or conical potential intersection in order to address the intriguing but overlooked interplay between dissipation and the topologically nontrivial Berry phase effect. We adopt the instanton approach with both symmetry analysis and accurate numerical solutions that consistently incorporate nonperturbative dissipation and the Berry phase. It reveals a unique and interesting dissipative quantum interference phenomenon with the Berry phase effect. The phase diagram of this tunneling exhibits Kramers degeneracy, nonmonotonic dependence on dissipation, and a generic dissipation-driven phase transition of quantum interference, before which an unconventional dissipation-enhanced regime of quantum tunneling persists.

Chris Philippidis, Christopher Dewdney, Basil J. Hiley

M. J. Rave

We show that quantum interference can be classically interpreted in terms of a phase invariant quantity, not unlike the Berry's phase. Under this interpretation, closed loops in time become fundamental quantum entities, and all quantum states become periodic. Decoherence is then seen to occur naturally as a consequence. This formalism, although counterintuitive, provides a useful way of assigning ``classical'' meaning to quantum probabilities.