Ben Sprott

462 reputation

bio	website	cs.mcgill.ca/~bsprot1
	location	Ottawa
	age
visits	member for	1 year, 6 months
	seen	Jun 13 at 13:37
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In 2004 I graduated from Waterloo where I was a member of the Perimeter Institute and worked with Lucien Hardy on a problem in quantum automata theory. I then started reading Baez, Coecke and Isham and decided I wanted to do category theory. In 2008 I started at McGill where I was a research assistant to Dr Panangaden and worked on both categorical quantum mechanics and the quantum causal dynamics. Now I am attempting to provide novel uses of the theory of categories for physics and economics. Also, I am interested in the concept of "idealization of structure" where compact elements in a collection of categories express this. I have several posts at the nforum where I talk about more pure mathematical ideas.

	462 reputation	bio	website	cs.mcgill.ca/~bsprot1	visits	member for	1 year, 6 months
17 badges		location	Ottawa		seen	Jun 13 at 13:37

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Mar 25	comment	fixed input qubit state to an arbirary pure state using two variable rotations and one fixed rotation David, thank you, yes I think the problem is the same. I just need some help in writing down a form for the operation (unitary transformation or Euler rotation) that highlights the order of operations. I, myself, can't derive the form by hand.
Nov 1	comment	can we cast physics as an interface to underlying structure? I realize I am pushing the line here, but lets just see where this goes.
Oct 11	comment	decoherence free subspace of a single photon I am thinking of fiber optic spans. The most likely cause of decoherence is second order polarization mode dispersion. There are no treatments of this subject in terms of a joint frequency and polarization linear operator. If you know of one, that would help. Generally, frequency is taken as a classical variable.
Aug 27	comment	polarization and frequency of a single photon I am not sure how to simultaneously measure these at spacelike separation. Usually, to measure frequency, you split the path according to frequency (prism or grating) and then do a destructive measurement of position at the end of the path which selects the given frequency. Similarly for polarization, you put a polarizing beam splitter and measure at the end of the path that selects a given polarization....seems like a neat problem.
Jul 13	comment	Can quantum field theory be seen as an epistemic restriction on (quantum) causal structure I suppose stat mech leading to thermodynamics is another example.
Jul 13	comment	Can quantum field theory be seen as an epistemic restriction on (quantum) causal structure I will quickly respond to Terry's comment. In fact, deriving any kind of physics from an epistemic restriction is very hard. That is why Spekken's Toy Model was so important and unique.
Jul 10	comment	Can quantum field theory be seen as an epistemic restriction on (quantum) causal structure Hi, Thanks both for your comments.
Jun 22	comment	The (co)algebra for the (co)monad of a light switch I think that there are two important monads. The first is the one that I described above and that monad indicates that there is a causal connection. The second monad would map every morphism to the identity and it indicates that there is no causal connection.
Jun 19	comment	The (co)algebra for the (co)monad of a light switch Still, excellent work! Let me play with it a bit, though off hand it loses some of the spirit. I was certainly hoping for a monad here.
Jun 19	comment	The (co)algebra for the (co)monad of a light switch Hi, There are four morphisms. You neglect the two constant maps. I did not restrict to the functions that form a group.
Jun 7	comment	Analogies between physics and packet-switched networks You can look at my paper on this subject.
May 17	comment	Convert state Vectors to Bloch Sphere angles Sure, I`ll do that more. I didn`t understand that I could give back to people answering simply by upping their numbers. I like the community and will try to do better as a member
Mar 13	comment	Krauss operators for random unitary THanks, the form suggested in the answer is the one I am interested in, though your comment is also useful!
Feb 28	comment	Unknown quantum state with promise of classical data What if instead of receiving $K$ copies of a state, you can receive $k$ copies of $N$ states chosen randomly from $S$. That is to say, you receive a string of qubits, and you get $K$ copies of each qubit. Given some setup, you will accumulate 4 different probability distributions because you are also allowed to know when a qubit has been passed. Can you not then use this added information to decide on which distribution corresponds to which original state? There is certainly information embedded in the promise of 4 different distributions and I guess I am trying to squeeze that out.
Feb 28	comment	Unknown quantum state with promise of classical data I guess I should have paid more attention in QInformation class.... :(....let me see if I can make this an interesting question.
Dec 2	comment	laser spectral width vs. linewidth I am still a bit lost, though. In this paper, Agrawal defines data error rates in terms of the "spectral width"link
Dec 2	comment	laser spectral width vs. linewidth Ok, thanks again!
Dec 2	comment	laser spectral width vs. linewidth Yes, the data I am looking at is for an ECDL and it is a datasheet. Thanks for the great answer! I have looked at the spectral plots for the laser (on datasheet) and the width 20 dB down from peak (power vs lambda) is indeed around 60 pm so I don't think that spectral width refers to tunability. Another point is that "reach" or "distance limit" quoted by manufacturer corresponds to a spectral width of 60 pm and that spectral width is sigmaL in equation 1 here
Nov 26	comment	Quantum causal structure An experiment involves transformations of an apparatus (the comonoid), but this is just an interface to a....quantum causal structure? The forgetful functor from string diagrams in the category of comonoids to diagrams in the underlying category is the probing of the quantum causal strucutre in terms of diagrams in the classical category.
Nov 26	comment	Quantum causal structure It is natural to consider different kinds of causal structure. I see the classical causal structure as having more to do with the causal diagrams which we can readily observed of an apparatus. But more and more research these days is demonstrating that apparata are likely classical structures in a quantum category like a categeory of comonoids in a monoidal category.