Search This Blog

Monday, November 10, 2008

Fine Structure Constant from Graphene

Pi divided by the fraction of light transmitted through a single layer of graphene gives the reciprocal of the fine structure constant.

1. de Broglie wavelength of slow neutrons----------------137.03601082

2. AC Josephson effect in superconductor junction--------137.059770

3. Quantum Hall effect-----------------------------------137.0360037

4. Anomalous magnetic moment of electron---------------137.03599976

5. Anomalous magnetic moment of positron---------------137.03599976

6. Muonium atom----------------------------------------137.0359940

7. Helium spectrum--------------------------------------137.035853

8. Velocity of hydrogen 1s electron /velocity of light-------137.0388

(All values were obtained from book called "Hydrogen" published by Harvard University Press in 2002 by John S. Rigden)

Definition of the Meter

The latest in a long line of ways to determine the length of a meter is based on mode-locked femtosecond lasers and an optical frequency comb technique. A Nobel Prize was awarded in 2005 for this work.

Tuesday, November 4, 2008

Quantum Computers from Graphene

Researchers at the University of Leeds are looking for new ways to construct quantum computers using graphene.

The image below is an image of a magnetic field created by d-wave superconductivity.

There are various ways of creating the necessary double degeneracy for encoding a qubit.

D-wave superconductivity is being studied by IBM in thallium-copper-oxide high-temperature superconductors, as well as, in graphene. Below is a method of creating two Josephson junctions in single layer graphene. A gate voltage is used to tune either of the junctions to a pi phase. This pi phase regime implements the qubit.

In another variant, a d-wave Josephson junction could be tuned to create the doubly degenerate ground states. Other variants have also been by proposed by Guido Burkard's team at the University of Konstanz and others.