Stanford Synchrotron Radiation Lightsource
Date Published: March 30, 2009

Macroscopic Quantum Insulator State Observed
summary written by Raven Hanna

One of the strangest consequences of quantum mechanics is the seemingly instantaneous communication of subatomic particles over long distances. Known as quantum entanglement, pairs or groups of particles can become linked so that any changes made to one will cause the others to respond quicker than the time it takes for light to travel between them.

Scientists are interested in finding a material that shows quantum entanglement on a macroscopic scale but which is neither a superconductor nor a superfluid. Dubbed a topological insulator, this theorized, exotic state of matter would have unusual conducting properties. For example, changes in the shape of the surface or edge of this material would not affect its conductance, unlike typical insulators. Such a material is both interesting as an exotic new state of matter and could have application to quantum computers since its information processing properties are insensitive to the presence of impurities, making quantum operations naturally fault-tolerant.

An international collaboration of scientists led by M. Zahid Hasan of Princeton University performed angle-resolved photoemission spectroscopy studies on SSRL's Beam Line 5-4 to measure the properties of the entangled electrons in a proposed topological insulator material made from bismuth and antimony. Combined with data from experiments performed at the COPHEE beam line of the Swiss Light Source, the study confirmed that the material is fully quantum entangled. This is the first example of a three-dimensional topological insulator in nature.

Additionally, this study defined a general method for identifying and characterizing other topological insulator states of matter. Their results were published in the February 13 edition of Science.

To learn more about this research see the full Scientific Highlight

D. Hsieh, Y. Xia, L. Wray, D. Qian, A. Pal, J. H. Dil, J. Osterwalder, F. Meier, G. Bihlmayer, C. L. Kane, Y. S. Hor, R. J. Cava and M. Z. Hasan, "Observation of Unconventional Quantum Spin Textures in Topological Insulators", Science 323, 919 (2009). [Primary P.I. : M.Z. Hasan (Princeton University)]

SLAC National Accelerator Laboratory
Stanford University