Detection of geometric phases in superconducting nanocircuits

When a quantum-mechanical system undergoes an adiabatic cyclic evolution, it acquires a geometrical phase factor1 in addition to the dynamical one; this effect has been demonstrated in a variety of microscopic systems2. Advances in nanotechnology should enable the laws of quantum dynamics to be tested at the macroscopic level3, by providing controllable artificial two-level systems (for example, in quantum dots4 and superconducting devices5,6). Here we propose an experimental method to detect geometric phases in a superconducting device. The setup is a Josephson junction nanocircuit consisting of a superconducting electron box. We discuss how interferometry based on geometrical phases may be realized, and show how the effect may be applied to the design of gates for quantum computation.