Road to new quantum computers
doi:10.1038/nindia.2009.144 Published online 30 May 2009
An Indo-US team has propounded new theoretical base for composite fermions, quasi-particles formed by electrons attached to magnetic flux quanta1. Such particles evolve when electrons are exposed to a transverse magnetic field. The researchers believe that their theoretical calculations will have implications in the realms of superconductivity and superfluidity.
When a two-dimensional electron system is exposed to a strong transverse magnetic field, it forms a new quantum liquid, whose investigation has produced some of the most beautiful emergent structures discovered in physics during the past quarter century. The most dramatic manifestation of this new phase of matter is the fractional quantum Hall effect (FQHE).
The researchers resorted to standard spherical geometry, subjecting electrons moving on the surface of a sphere to a radial magnetic field. They studied systems with 50, 100 and 200 particles and found a new collective mode in the behaviour of composite fermions. Their theory also obtains the full dispersion of the new collective modes, which is outside the range of Raman experiments, but possibly observable in photoluminescence experiments.
"In a broader sense, the FQHE provides a new paradigm for collective behavior in nature, which is as interesting and fundamental as superconductivity and superfluidity," says lead researcher Jainendra Jain. There is intense interest in the nature of the excitations of the FQHE, believed to satisfy exotic properties that some believe might be useful for quantum computation, he adds.
The authors of this work are from: Department of Theoretical Physics, Indian Association for the Cultivation of Science, Jadavpur, Kolkata, India, Davey Laboratory, Physics Department, Pennsylvania State University, University Park, Pennsylvania, USA.
- Majumder, D. et al. Collective excitations of composite fermions across multiple Λ levels. Nat. Phys. doi: 10.1038/nphys1275 (2009) 10.1038/nphys1275