Measurement of Geometric Phase for Mixed States Using Single Photon Interferometry
Marie Ericsson, Daryl Achilles, Julio T. Barreiro, David Branning, Nicholas A. Peters, Paul G. Kwiat · Physical Review Letters · 2005
Geometric phase may enable inherently fault-tolerant quantum computation. However, due to potential decoherence effects, it is important to understand how such phases arise for mixed input states. We report the first experiment to measure mixed-state geometric phases in optics, using a Mach-Zehnder interferometer, and polarization mixed states that are produced in two different ways: decohering pure states with birefringent elements; and producing a nonmaximally entangled state of two photons and tracing over one of them, a form of remote state preparation.