Last week papers (18th week of 2012)

From 22 to 28 of April 2012, well it was really from 22 to 26 as I took a long weekend off the office...

Published

• "Quantum Computing with Incoherent Resources and Quantum Jumps" by  M. F. Santos et. al., Physical Review Letters 108, 170501 (2012).
  
  
  So, let us say that you have logarithmic spare time and want to make nature do computation for you. Well, Marcelo and coauthors have just show that, in principle, you just need time, patience, clickers and a way to put/remove them clickers from your open system. 


• "Optical Forces and Torques in Nonuniform Beams of Light" by D. B. Ruffner and David G. Grier, Physical Review Letters 108,  173602 (2012).
  
  
  I don't remember seeing an optical tweezer paper in PRL. The authors analyze linear and angular momentum densities of light beams to show how amplitude, phase and polarization profiles contribute to optical forces. One interesting thing they found is how the curl of the spin angular momentum can exert torque on objects without contributing to the orbital angular momentum of the beam. 


• "Equilibrium and disorder-induced behavior in quantum light–matter systems" by E. Mascarenhas et. al., New Journal of Physics 14,  043033 (2012).
  
  Coupled two-level system cavity arrays in the polaritonic regime have been proposed to realize the Bose-Hubbard model and Insulator-Superfluid transition  in the past. Now, by using a mean field approach the authors study the effects of disorder on the phases of the Jaynes-Cummings-Hubbard model and find glassy phases using entanglement measures. Interesting, ain't it?  

Preprints

• "Supermodes of Hexagonal Lattice Waveguide Arrays" by J. S. Brownless et. al., arXiv: 1204.4974v1 [quant-ph].
  
  
  A modal approach to hexagonal  photonic waveguide arrays. I'm still trying to follow it and get their results and see if it helps me solve some other waveguide lattices.


• "Relating the quantum mechanics of discrete systems
  to standard canonical quantum mechanics" by G. Hooft , arXiv: 1204.4926v1 [quant-ph].
  
  So, imagine you are working near the Planck scale and you want to see if there's something happening there, most probably you want to go from continuous to discrete modelling of the system. Well, here's an approach focused on applications to the harmonic oscillator. I need time to sit down and follow this, discrete dynamics is always interesting for me.


• "Dynamical scattering models in optomechanics: Going beyond the `coupled cavities' model" by A. Xuereb and P. Domokos  , arXiv: 1204.5301v1 [quant-ph].
  
  
  An analysis of membrane-coupled cavities from first principles. In short, we are safe using the coupled-cavities simplification if the coupling element reflectivity is not way below 50% .


• "Morse potential derived from first principles" by R. Costa Filho et. al., arXiv: 1204.5931v1 [quant-ph].
  
  I .

Last week papers (17th week of 2012)

Without further ado...

Published

• "Quantum phase transition in the Dicke model with critical and noncritical entanglement" by  L. Bakemeier, A. Alvermann and H. Fehske, Physical Review A 85, 043821 (2012).
  
  
  A phase transition analysis on the Dicke model exploring the behavior of the system when the frequency of the field mode tends to zero, called the classical oscillator limit by the authors, where the model goes to a Lipkin-Meshkov-Glick model. Why people don't cite us? Really... 

• "Ultimate limits to quantum metrology and the meaning of the Heisenberg limit" by M. Zwierz, C.A. Perez-Delgado and Pieter Kok, Physical Review A 85,  042112 (2012).
  
  
  I remember being at a seminar where Carlos presented this work in CQT. It's a mashup of query complexity with quantum mechanics to reformulate a Heisenberg limit for quantum metrology based on the idea of physical resources. 

• "Ginzburg-Landau theory for the Jaynes-Cummings-Hubbard model" by Christian Nietner and Axel Pelster, Physical Review A 85,  043831 (2012).
  
  
  As  you know, I like anything Jaynes-Cummings or Dicke. A while ago some people decided to study what happens when you couple cQED building blocks (cavities with an atom inside) and used a polaritonic approach to the problem to describe an isulator and superfluid phase of the system. So, it is nice that a phenomenological theory of superconductivity is used to describe the superfluid phase of the system! 

Preprints

• "Non-Markovian quantum dynamics and classical chaos" by I. Garcia-Mata, C. Pineda and D. Wisniacki, arXiv: 1204.3614v1 [quant-ph].
  
  
  The authors study a system coupled to an environment with different levels of chaos and analyse how well a chaotic environment models Markovian evolution.


• "Theory of optomechanics: Oscillator- eld model of moving mirrors" by C.R. Galley, R.O. Benhunin and B.L. Hu, arXiv: 1204.2569v1 [quant-ph].
  
  
  A nice theory of coupling between a field and a moving mirror from first principles that converges to models used in the literature. I was more interested in the convergence to what they called the N x coupling that we widely use in Quantum Optics.


• "Superradiant quantum phase transition in a circuit QED system: a revisit from a fully microscopic point of view" by D.Z. Xu, Y.B. Gao and C.P. Sun, arXiv: 1204.2602v1 [quant-ph].
  
  
  The authors derive the Dicke Hamiltonian from a microscopic model circuit-QED involving superconducting qubits and a quantized field. These model allows for a so-called superradiant phase transition in contrast to a previous analysis in the literature.


• "Exact solution to the quantum Rabi model within Bogoliubov operators" by Q.H. Chen, C. Wang and K.L. Wang, arXiv: 1204.3668v1 [quant-ph].
  
  It is a nice step by step demonstration of how to get a exact solution for the quantum Rabi model with an additional tunneling. The authors recover Braak's solution. I personally love the closing paragraph.

The Russian Solution to the quantum Rabi Model

There's a frightful phrase in physics that goes "a Russian solved it a while ago."

A while ago a very nice paper of D. Braak appeared discussing the integrability of the quantum Rabi Model in Physical Review Letters. This is a nice elegant paper using a discrete symmetry to show that the model is  integrable and gives an exact spectrum for the model [Phys. Rev. Lett. 107, 100401 (2011)].  

The one interesting thing is that the spectrum for the quantum Rabi model was shown by É. A. Tur by resolvent theory eleven years before [Optics and Srectoscopy 89, 574-588 (2000) (English) Optika i Spektroskopiya 89, 628-642 (2000) (Russian)]. If someone can find a pdf file please email it to me, I could only get a bad scan of a battered photocopy.

And don't get me wrong, Braak's paper contribution goes beyond the spectrum. He explores the implications that symmetries has on integrability for models that doesn't have a classical limit/analogue.

Also, a little bit further in time, J. Casanova et. al. analyzed the spectra and dynamics of the quantum Rabi model in the deep strong coupling regime [Phys. Rev. Lett. 105, 263603 (2010)] and presented an approximated spectra for the model and the curious collapse and full revival of the ground state of the positive parity chain.

Again, that particular oscillatory behavior for the same state was discussed by É. A. Tur but for weak coupling in [Optics and Spectoscopy 89, 574-588 (2000) (English) Optika i Spektroskopiya 89, 628-642 (2000) (Russian)] and an elegant approximation to the spectra leading to their result in [arXiv: 0211055 [math-ph]].

And don't get me wrong again, Casanova et. al. study the deep ultrastrong coupling and delve in the analysis they are presenting by adding a phase space analysis and some numerical analysis on the topic.

My point is that some of the results in both Physical Review Letters has been known for ten years already and nobody cited the work of É. A. Tur. A simple Google search of "Jaynes-Cummings model  without rotating wave approximation" brings Tur's paper in the second place, did the editors or reviewers even bother?

Now, surely there's a dozen papers in the review queue that are working on the topic and citing Braak and Casanova—which is the right honest thing to do—but is someone citing Tur? Show the guy some love, his work is nice, clean and elegant.


Edit: I forgot to mention that Tur's result was for weak coupling, g=0.5.

Last week papers (16th week 2012)

Now, Happy belated easter; writing in advance is really confusing because today is the first week of Easter and this will not see light until the second... and I'm rambling... back to business, the interesting things on the physics 'tubes from April 9th to 15th...

Published

• "Observation of the Kinetic condensation of classical waves" by  C. Sun,  et. al., Nature Physics (2012).
  
  
  This I want to read, a few years ago I think I saw a paper on the topic—give me a second...this one and this one in PRL—and it really got my eye. Now, that's something I want to learn about, it seems fun and interesting.

• "Tavis-Cummings model beyond the rotating wave approximation: Quasidegenerate qubits" by S. Agarwal, S.M. Hashemi Rafsanjani and J. H. Eberly , Physical Review A 85,  043815 (2012).
  
  
  As Rabi model has come back, it was not long before the many two-level system version should appear back in press. Here the dynamics in a particular regime where the energy gap of the two-level system  is way smaller than the frequency of the field is explored with strong coupling via an adiabatic approximation known for the same regime but for a single two-level system interacting with a field.

Preprints

• "Can free will emerge from determinism in quantum theory?" by G. Brassard and P. Raymond-Robichaud et. al., arXiv: 1204.2128v1 [quant-ph].
  
  
  They push a deterministic, local and realistic interpretation of quantum mechanics, this never gets old at all and now we have a "parallel lives" added to the zoo of interpretations. If you like interpretations, philosophical speculation and so, this is for you  


• "Producing and measuring entanglement between two beams of microwave light" by E. Flurin et. al., arXiv: 1204.0732v1 [quant-ph].
  
  
  I'm too lazy to read it today but entanglement between beams of microwave is interesting. 


• "Thermal phase transitions for Dicke-type models in the ultra-strong coupling limit" by M. Aparicio Alcalde et. al., arXiv: 1204.2271v1 [quant-ph].
  
  
  I like almost everything related to Dicke model, here a study of thermal phase transitions of the mathematical model is presented. I like papers involving Emary and Brandes, they are nice reads.

Last week papers (15th week 2012)...

I told you about the Nature Physics Insight on Quantum Simulation, so I will skip those 

Published

• "Ultra-high Q mechanical oscillators through optical trapping" by  D. E. Chang,  et. al., New Journal of Physics 14, 045002(2012).
  
  
  This is interesting: Reaching the quantum ground state of a mechanical oscillator at room temperature.The authors propose the use of optical forces to free a the characteristics of a mechanical structure from its material properties.

• "Collapse-revival dynamics and atom-field entanglement in the nonresonant Dicke model" by A. Alvermann, L. Bakemeier and H. Fehske, Physical Review A 85,  043803 (2012).
  
  
  A numerical studies of Rabi model, it's all coming back again and again and again. They study collapse and revivals out of resonance. 


• "Stimulated Emission from a Single Excited Atom in a Waveguide" by E. Rephaeli and S. Fan, Physical Review Letters 108, 143602 (2012).
  
  
  It's stimulated emission in a single-atom confined in a waveguide scenario. .


• "Uncertainty Relation for Photons" by I. Bialynicki-Birula and Z. Bialynicka-Birula,   Physical Review Letters 108, 140401 (2012).


Can you tell that I don't really want to write anything?

  
• "Solvability of the two-photon Rabi Hamiltonian" by I. Travenec, Physical Review A 85, 043805 (2012).
  
  
  I told you, it's the Rabi model again and again and again... here with two-photon transitions instead of one-photon.

  
• "Widely Tunable, Nondegenerate Three-Wave Mixing Microwave Device Operating
  near the Quantum Limit" by N. Roch et. al., Physical Review Letters 108, 147701 (2012).
  
  
  Now, the best for the last. I find this awesome, people are making better and better microwave resonators, emitters and now it is possible to do three-wave mixing in the microwave regime!

Preprints

• "Entanglement control in hybrid optomechanical systems" by B. Rogers et. al., arXiv: 1204.0780v1 [quant-ph].
  
  
  I'm too lazy to read it today but seems quite interesting...  


• "Producing and measuring entanglement between two beams of microwave light" by E. Flurin et. al., arXiv: 1204.0732v1 [quant-ph].
  
  
  I'm too lazy to read it today but entanglement between beams of microwave is interesting. 

Fear...

Fear is an emotion caused by a perceived threat (real or imaginary).

Fear is a kind of survival mechanism, an automatic response that prepares mind and body for the unknown; a really bad unknown. 

Fear, reigned, may lead to acts beyond our idea of human capabilities or, unreigned, to crushing anxiety crippling life at the innermost sanctuary of the mind. 

I had never felt fear living in Mexico. Now I do and I'm not even in my homeland. No more than five years ago, the sight of a random guy walking aimlessly the parking lot during the wee hours just made me think of a dude smoking a cigarette or waiting for his friends to keep the party on; now, it kept me looking through the window for the half hour the dude was there, searching for security's phone in the emergency sheet at the door and wondering where the fuck was the security guard whose snoring bothered me all the nights before that night. 

I never thought I would get to that. I never thought I would stop taking the overnight bus home to visit mom or giving up driving uncountable hours by day or night during vacations. I gave those up no more than five years ago. 

I know what it is to live a normal life with normal fears and that's either in the so far untouched center of Mexico (Puebla and Queretaro seem to be the less conflictive) or far from this beautiful country. Sad but true.

Fuck fear!

It's Quantum Simulation issue in Nature Physics Insight!

I can tell you that this is one of  Feynman's most beautiful phrase and I use it as often as possible in my presentations as opening slide:

 “Nature isn't classical, dammit, and if you want to make a simulation of nature, you'd better make it quantum mechanical, and by golly it's a wonderful problem, because it doesn't look so easy.”

That's the opening phrase for Trabesinger's editorial on the current issue of Nature Physics that includes a commentary by Cirac and Zoleer and reviews by Bloch, Dalibard & Nascimbéne, Blatt & Ross, Aspuru-Guzik & Walther, and Houck, Tureci and Koch.

Enjoy! I know I will...

Last Week Papers (14th week 2012)

It feels good to be back in an office and able to follow the literature. I'm thinking that I like the list format and now will split it in two: published and pre-prints because it is good to talk about pre-prints.

Published

• "Quantum Interface between an Electrical Circuit and a Single Atom" by  D. Kielpinski,  et. al., Physical Review Letters 108, 130504 (2012)
  
  
  They have shown it may be possible to couple an ion to a quantized current from a superconducting circuit. That's nice as the experiments in classical coupling of currents and ions can be used to build upon them and get to this. Interesting read.

• "Optical Detection of the Quantization of Collective Atomic Motion" by N. Brahams et. al., Physical Review Letters 108, 133601 (2012).
  
  
  They are measuring the collective motion of a gas coupled to a cavity field. That impresses me.


• "Superradiance in spin- j particles: Effects of multiple levels" by G._D Lin and S. F. Yelin, Physical Review A 85, 033831 (2012).
  
  
  It has always been a problem to talk about superradiance in two-level systems. Physically sound models with two-level systems involve Raman pumping to auxiliary levels in 4-levels schemes. It has always been mentioned that it may be possible to have superradiance with multi-level atoms. Well, they calculate it and show the effect of multi-level atoms in radiance, decay and so on...


• " A heuristic approach to BEC self-trapping  in double wells beyond the mean field" by K. Rapedius,  Journal of Physics B: Atomic, Molecular and Optical Physics 45, 085303 (2012).


A semi-classical analysis of the Bose-Hubbard dimer Hamiltonian with some curious variations that seem to help producing some approximations that may be valid in the mean-field and finite particle number cases.

  
• "Effects of orbital angular momentum on the geometric spin Hall effect of light" by L.-J. Kong, Physical Review Letters 85, 035804(2012).
  
  
  Reading it and trying to figure it out... I have never read about the spin Hall effect of light and it seems like there are two different kinds: one at a gradient refractive index interface and another that is geometric and relates to observation from a frame tilted with respect to the propagation direction. I need to read more about all this things.

Preprints

• "Exact real-time dynamics of the quantum Rabi model" by F.A. Wolf, M. Kollar, and D. Braak, arXiv: 1203.6039v1 [quant-ph].
  
  
  Last year Braak wrote a very nice PRL where he presented the proper system of Rabi model; now, this follow-up paper builds upon the basis presented before and analyses the dynamical behavior in different time regimes. I wonder why nobody cites E. A. Tur's papers on approximations to the eigenvalues of Rabi model. Anyway,  This manuscript is quite interesting and a must read if you work in Quantum Optics.  


• "Quantum thermometry using the ac Stark shift within the Rabi model" by K.D.B. Higgins, B.W. Lovett, and E.M. Gauger, arXiv: 1203.5994v1 [quant-ph].
  
  
  I have the feeling that whenever I get to grasp what they are doing I'm gonna like it.