Geometry in Noise

An international team of condensed matter researchers, including ICTP physicist Mikhail Kiselev, has published a paper titled 'Geometric Quantum Noise of Spin' in the current edition of Physical Review Letters (DOI: 10.1103/PhysRevLett.114.176806). The paper predicts that geometric phases (a phase difference that affects the dynamics of systems in both classical and quantum worlds) might enter into 'noise' sources, and this in turn can be detected by measuring the behavior of systems such as nano-magnets.

In the quantum world, noise is responsible for a mechanism known as dephasing that facilitates the transition of a quantum behavior to a classical one. The team showed that the presence of geometric phases in noise sources could affect the behavior of nano-structures, for example, cause fuzzy magnetic moments (the measure of an object's tendency to align with a magnetic field) in nano-magnets. Kiselev says that the paper provides an efficient protocol for experimental observation of the “geometric noise” in the magnetization dynamics through the detection of the Langevin forces. The ideas developed in the paper can have broader applications, such as in spintronics.

The complete paper may be accessed from the Physical Review Letters website.