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location Seattle, WA
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seen Nov 17 '12 at 18:50

I am a medical researcher and quantum systems engineer, whose experimental research interests focus upon quantum spin imaging and metrology, and whose theoretical interests focus upon large-scale quantum simulation, in overall service of advances in regenerative medicine.

For a non-technical overview of this research, see the (open-source) PNAS article "Spin Microscopy's Heritage, Achievements, and Prospects." For in-progress research see the Soldier Healing Seminar "Green Sheet Notes for 2013".

Quantum transport phenomena is a topic of particular interest, as efficiently simulated within frameworks in which large-dimension Hilbert-space gauge-field dynamics is emergent as the natural algebraic resolution of low-dimension varietal dynamics.


Sep
24
comment How did QED diverge from quantum mechanics mathematically?
The dynamical flow associated to the classical Bloch equations is Hamiltonian ... and yet there is no geometrically natural Lagrangian state-space potential (that is, no global singularity-free Lagrangian) associated to classical Bloch flows. Why should quantum Hamiltonian flows be any different? That is why spin degrees of freedom appear in path-integral formulations of quantum field theory in, as Feynman says in his 1948 article, "a purely formal way"--nowadays expressed in terms of Grassmanian variables--that, in Feynman's phrasing, "adds nothing to the understanding of these equations."
Sep
20
comment A good example of a nonlinear symplectomorphism?
The Bloch equations, viewed as a Hamiltonian flow on $S^2$. The symplectomorphism is rotation of the Bloch sphere.
Aug
30
comment Reversing gravitational decoherence
@John Preskill , with a view toward clarifying the various subtleties and imprecisions associated to notions like "dressed particles" and "mirrors", the literature survey below has been augmented to show how modern ideas from quantum information theory serve to naturalize and universalize the 20th century understanding of global conservation and local transport processes that is due to Dirac, Onsager, Casimir, Callen, Landau, Green, Kubo, etc. Even today, there is plenty that we do not understand about "dressed particles" and "mirrors."
Aug
29
comment Reversing gravitational decoherence
When account for all of the known physical processes by which particles are "dressed" by zero-mass bosonic vacuum excitations (whether electromagnetic or gravitational) then it becomes less evident that we should be entirely confident that high-order quantum decoherence is reducible to scalably-low levels. In particular, collective ("superradiant") dynamical decoherence is ubiquitous; e.g., the teaching of the Casimir effect (Landau and Lifshitz, Theory of Continuous Media) is that no mirror is decoherence-free. Some physical idealizations (e.g., perfect mirrors) are just plain wrong!
Aug
29
comment Reversing gravitational decoherence
Still more concretely, all quantum experiments/observations accomplished to date, and all accurate quantum chemistry/physics simulations (known to me) can be accurately unravelled (AFAICT) on state-spaces whose stratification rank is $r \sim \mathcal{O}(nd(2j+1))$, where $n$ is the number of particles, $d=3$ is the spatial dimension, and $j$ is the spin. Needless to say, there are considerable nuances associated to this poly-dimension state-space scaling law ... presumably Nature "knows" the natural basis for minimal-rank/high-fidelity state-space stratifications, but we have to guess at it.
Aug
29
comment Reversing gravitational decoherence
Scott, your comment is like "Your arguments seem to give no concrete guidance about the magnitude of the radius of the universe." To answer concretely, I'd have to specify (for example) the rank-indexed stratification of the universal state-space. In this regard, the lowest rank that I'm comfortable asserting is ... uhhh ... maybe 137? Seriously, experiments to bound the rank and/or curvature of quantum state-spaces surely will prove comparably challenging to general relativity experiments. Well heck, that's GOOD!
Aug
29
comment Reversing gravitational decoherence
LOL ... maybe I'd better say too, that I told Aram Harrow yesterday that I'd let these ideas lie fallow for a few days ... on the grounds that some tricky practical considerations regarding the efficient simulation of quantum transport are associated to them! And so, there is a pretty considerable chance that in the next week or so, some of the above points will be reconsidered (by me) and extended or rewritten. Therefore Scott, please consider your question to be answered in the same spirit it was asked. That is why both your question and your comments (above) are greatly appreciated. :)
Aug
29
comment Reversing gravitational decoherence
Scott, I think we may even agree, though we prioritize our main points differently. For me, the main point is that any quantum theory that provides thermodynamically consistent descriptions of localized transport of globally conserved quantities must entail non-unitary flow on a non-flat low-dim Kahlerian state-space. Your point too is valid --- even equivalent! -- namely Zeilinger-type buckyball experiments succeed iff transport of the conserved quantity (mass) is not spatially localizable. And this accords with our everyday experience that QM is locally Hilbert, globally not, eh?
Aug
27
comment An example of non-Hamiltonian systems
@Yrogirg, in the macroscopic equations, there is no friction. At the microscopic level, you have asked a deep question! Namely, can quantum mechanics encompass rolling/sliding mechanical constraints that have zero entropy gain? I do not know the answer to this question, and I suspect that no one does.
Aug
25
comment An example of non-Hamiltonian systems
@Ron, I have added a some definitions and a reference that makes the point more clear.