Thursday, December 15, 2011

Spectroscopy of a black hole and its horizon entropy

The idea of Isolated and Dynamical Horizon theory was first worked out by Heyward in 1994. He derived the complete definition of a marginally null surface that is trapped on a black hole horizon.

A few years later Ashtekar and his colleagues re-wrote the same theory in the language of Ashtekar- Sen variables. Before this development Rovelli has argued that a black hole entropy should be proportional with its horizon area. Lee Smolin linked loop quantum gravity to topological field theory and argued that a black hole should be described by a Chern Simon’s action.

Later on, Krasnov based on all the above mentioned ideas argued the derivation of a black hole entropy from the counting of puncture states. A ‘sequence’ of punctures on a horizon explains the wave function of the horizon. Being a sequence, the punctures are ordered and this make them distinguishable. However, there is no physical evidence why should one restricts the wave functions into a sequence and not a set of punctures in which there is no generic order, thus no distinguishability.

Given this in the quantum horizon theory, I noticed an internal degeneracy in the nature of area operator. Since the area eigenstates are insensitive to the completely tangential edges residing on the horizon, the edges describing a quantum surface carries a local distinguishability. The complete spectrum of area provides the Bekenstein-Hawking entropy, which using Olaf Dreyer’s conjecture it becomes consistent with the evaporation of minimal area cell with the corresponding area of the highly damping quanta.

This proposes a kinematical picture for defining a quantum horizon via spin foam models, however the dynamics of such a model has not yet initiated to be studied. . A new value was devoted to the Immirzi parameter. Considering the full spectrum of area and using the semi-classical conjecture that on a black hole the horizon area and the hole energy are proportional

I noticed a strong amplification in some selected frequencies radiated away from a black hole due to its horizon fluctuations. The full spectrum of a black hole radiation was extracted and the bright lines in the spectrum turn out to be unblended and narrow enough to become observable.

Tuesday, December 13, 2011

Josephson and Feynman in low temperature!

We recently calculated noise power spectrum due to the presence of magnetic impurities in a Josephson junction explicitly, using Feynman diagrams. The long paper includes all details of integrations and calculations.

The results were presented is written in a way that serves as a good source to understand step by step the details of analysis of decoherence in mesoscopic superconducting systems that includes the Kondo effect through the Coulomb interactions Feynman diagrams in low temperature.

It was recently published in PRB in 19 pages.

Saturday, September 03, 2011

Strom in Waterloo, Ontario

I took this photo tonight from my balcony at Waterloo, where I was spectator of a rain storm. after many attempts I finally succeeded to take this shot from a lightning.

Sunday, August 28, 2011

Irrelevant news from nature to loop quantum gravity

Today I read this article from BBC that LHC results put supersymmetry theory in trouble.

The results do not rigorously demonstrate anything because Strings can exist without low-energy supersymmetry of Loops with supersymmetry. I do not understand why the community of loop quantum gravitists are this much happy about it?! Its certainly bad news for preliminary string theory, but how about loop quantum gravity? Loop Quantum Gravity does not rely on superstring theory but it can certainly handle that. Loop quantum gravity certainly is an alternating theory, but there are many other candidates to seek for using the foundations of quantum mechanics.

But certainly this result is without doubt so important to be argued for a long time between experts.

Wednesday, August 17, 2011

The paper of Kondo noise ...

I and Frank worked on it, was accepted for publication in Physical Review B in the third week after submitted. This is a new score in short-time reviewing process perhaps because we paid it off from working on it for almost a year!

If you are working on the critical current noise in superconducting materials or in general you deal with superconducting qubits or SQUIDS, reading this paper is highly recommended.

You will find in it a good analytical approach to understand the complicated physics of a magnetic impurity inside a Josephson junction. With the consistency it provides with the Wilson type renormalization group method so far was used in the Kondo community, it equips us to study the critical current noise in a tunnel junction in the presence of a few free Oxygen molecules inside the tunnel junction oxide layer.

Tuesday, July 12, 2011

Theory Canada 6 in the city of Corner Brook in Newfoundland, Canada was exciting and interesting. The nature of the city is unique and the core idea of the conference was intriguing: some of the Canadian theorists who due to the wide geography of this country cannot meet each other in a regular base gather in one place a few days before CAP conference and collaborate on exchanging ideas and thoughts.

Mohammad H. Ansari

Thursday, June 23, 2011

Noise and microresonance of critical current in Josephson junction

Along with Frank Wilhelm I enjoyed working on the noise study of a Josephson junction. The results appeared today at

We analyze the impact of trap states in the oxide layer of a superconducting tunnel junctions, on the fluctuation of the Josephson critical current, thus on coherence in superconducting qubits.

Two mechanisms are usually considered: the current blockage due to repulsion at the occupied trap states, and the noise from electrons hopping across a trap. We extend previous studies of noninteracting traps to the case where the traps have on-site electron repulsion inside one ballistic channel.

The repulsion not only allows the appropriate temperature dependence of 1/f noise, but also is a control to the coupling between the computational qubit and the spurious two-level systems inside the oxide dielectric.

We use second order perturbation theory which allows to obtain analytical formulae for the interacting bound states and spectral weights, limited to small and intermediate repulsions.

Remarkably, it still reproduces the main features of the model as identified from the Numerical Renormalization Group.

We present analytical formulations for the subgap bound state energies, the singlet-doublet phase boundary, and the spectral weights.

We show that interactions can reverse the supercurrent across the trap.

We finally work out the spectrum of junction resonators for qubits in the presence of on-site repulsive electrons and analyze its dependence on microscopic parameters that may be controlled by fabrication.

Tuesday, March 29, 2011

Meet other creatures

Meet them in these scales of a meter:
  • 10^-35:  Quantum gravity domain. Planck's length.
  • 10^-30:
  • 10^-28:
  • 10^-24: Neutrino
  • 10^-21:  Perons, the ingredients of quarks.
  • 10^-18: Quarks. Electron cores.
  • 10^-15: Protons.
  • 10^-14: size of light nuclei.
  • 10^-12: Gamma ray wavelength. 
  • 2*10^-12: electron Compton wavelength.
  • 5*10^-12: X-ray wavelength.
  • 2.5*10^-11: distance between two Hydrogen atom nuclei.
  • 3.1*10^-11: distance between two Helium atom nuclei. 
  • 7.0*10^-11: distance between two Carbon atoms nuclei.  
  • 10^-10: distance between two Sulfure atom nuclei.
  • 5*10^-10: width of Protein alpha Helix.
  • 10^-9 (1 nano meter): Carbon nanotube.
  • 2*10^-9: the smallest transistor gate of microprocessor.
  • 3*10^-9: thickness of DNA.
  • 10*10^-9: the width of cell membrane.
  • 50*10-9: ultraviolate wavelength.
  • 90*10^-9: HIV.
  • 300*10^-9: Violate wavelength.
  • 500*10^-9: largest virus.
  • 600*10^-9: red light wavelength.
  • 7*10^-6 (7 micrometer): red blood cell.
  • 10*10^-6: infrared wavelength. Fog droplet. White blood cell. 
  • 50*10^-6: Pullen grain. Silt particle. 
  • 10^-4 (a tenth of milimeter): smallest things visible to naked eyes. Width of human hair.
  • 2.5*10^-4: human egg. 
  • 3*10^-4: computer pixel.
  • 5*10^-4: salt crystal grain. Thickness of human skin. Largest bacteria. Pencil lead.
  • 7*10^-4: thickness of credit card. 
  • 10^-3: Ant. Sesame. etc. 

Thursday, March 03, 2011

The Fritz London Prize 2011

is happy to hear the Fritz London Prize - highest award in low temperature physics after the nobel - is awarded to Hans Mooij in recognition for his experimental contributions to the understanding of nonequilibrium superconductivity, Josephson flux qubits, etc; at the same time to Gerd Schön in recognition of his theoretical contributions to the understanding of superconductivity in mesoscopic systems, including charge qubit; as well as to Humphrey Maris in recognition for his original theories and experimental discoveries in liquid helium, concerning phonons, Kapitza resistance, levitation, nucleation, electron bubbles and vortex imaging.

Thursday, February 03, 2011

Conference Announcement NCMT 2011

Another major event in the region of South Western Ontario for the community of nanostructure phyicisits:

International Conference on Frontier Topics in Nanostructures and Condensed Matter Theory
March 9-11, 2011at Western


Friday, January 21, 2011

The Kondo theory

Additional unwanted qubits in a phase qubit due to the Kondo effect.
Simmonds Phys. Rev. Lett 2005 
The Kondo effect is one of the interesting features of low temperatur physics where temperature is seen not to play as a smoother, instead it ruines the results taken from perturbation theory.   Last Monday I presented a talk titled "the Kondo effect" in a Colloquium at the Institute for Quantum Computing IQC in Waterloo.  It was a good opportunity to face with some interesting questions and comments...

In this talk I presented two exotic behavior of electron in low temperature, one in a quantum dot, and the second in the Josephson junction between two superconductors.  In a quantum dots I explained the Kondo plateaus predicted in 1988 by Glazman and Raikh in JETP Lett. and they observed by van der Wiel Science 2000. In the second half, I explained how this effect can causes the presence of additional unwanted qubits interacting with the computational qubit. And finally our recent idea of how to suppress them to prevent errors on computations...