tomography for QuTiP?

[Scott Glancy]

QuTiP was recently brought to my attention by some friends who were using it to model a superconducting qubit experiment.  It seems like a powerful tool, and I am interested in contributing to its development.  The main thing that I would like to add to the project is quantum tomography code.  I did not see any discussion of this in the documentation, and I think that it would be a very useful addition.

I have already written tomography software in Matlab, which I have used to analyze a few experiments at NIST, such as:
Quantum state tomography of an itinerant squeezed microwave field
F. Mallet, M. A. Castellanos-Beltran, H. S. Ku, S. Glancy, E. Knill, K. D. Irwin, G. C. Hilton, L. R. Vale, K. W. Lehnert
http://arxiv.org/abs/1012.0007

and

Generation of Optical Coherent State Superpositions by Number-Resolved Photon Subtraction from Squeezed Vacuum
Thomas Gerrits, Scott Glancy, Tracy S. Clement, Brice Calkins, Adriana E. Lita, Aaron J. Miller, Alan L. Migdall, Sae Woo Nam, Richard P. Mirin, Emanuel Knill
http://arxiv.org/abs/1004.2727

and a couple others in progress.  Also, my code uses an optimization algorithm that achieves faster convergence to the maximum likelihood state than the usual ("R*rho*R") method found in the literature.  Once maximum likelihood quantum state tomography has been integrated, I would be interested in also implementing some more sophisticated analysis tools such as those based on compressed sensing, process tomography, ...

Is this something that you would be interested in?

Scott Glancy

[jrjoh...@gmail.com]

Hi Scott

Thanks for offering to contribute your code! It sounds very interesting and we would love to include it in qutip. We only have some rudimentary process tomography code in qutip now, so your code would be very welcome addition. I suppose it is a code for performing tomography from experimental data measurement?

QuTiP development is hosted on github, so the best way for you to procede would be to fork our repository and create a pull request.

http://www.github.com/qutip

Rob

[Scott Glancy]

Rob,

The Matlab code that I have developed estimates a density matrix for a quantum state given a set of measurement data.  Is there existing code in QuTiP that can do this?

I noticed a reference to process tomography in the documentation, but that seemed to be limited to calculation and visual display of a chi-matrix (in a standard basis) from a given quantum map (or "density matrix propagator").  Calling that "tomography" might be a little confusing, because "tomography" usually means solving the statistical problem of estimating a quantum state or process from experimental data.

I am happy to interact through github.  It may take a few months before I am able to contribute much, because I need to finish-up a couple of other projects and learn Python. This seems like an exciting project, and I look forward to getting started on it.

Scott

[jrjoh...@gmail.com]

Hi again

The Matlab code that I have developed estimates a density matrix for a quantum state given a set of measurement data.  Is there existing code in QuTiP that can do this?

No, we don't have anything like that in QuTiP. In fact, there are no routines at all in QuTiP for processing experimental data, so your code would be a great addition in a new interesting direction!

 

I noticed a reference to process tomography in the documentation, but that seemed to be limited to calculation and visual display of a chi-matrix (in a standard basis) from a given quantum map (or "density matrix propagator").  Calling that "tomography" might be a little confusing, because "tomography" usually means solving the statistical problem of estimating a quantum state or process from experimental data.

Yes, that function only presents a numerically computed quantum map in the form of a process tomography plot. As you point out, it does not do any tomography in the sense of estimating the process from experimental data. 

 

I am happy to interact through github.  It may take a few months before I am able to contribute much, because I need to finish-up a couple of other projects and learn Python. This seems like an exciting project, and I look forward to getting started on it.

That sounds good, take your time. I'm looking forward to your contributions. If you start a pull request early on, we might also be able to help out with how to organise the code within qutip.

Rob

[Andrew M. C. Dawes]

Scott,

I am intrigued to hear about this and would be happy to offer my assistance if it is of any use. I've been using qutip for about two years in an instructional setting, and casually in my own research. I also do quite a bit of python coding, but would still consider myself a physicist-programmer and not the other way around :-)

Perhaps more useful, is that I'm also in the quantum state tomography business so could potentially help bridge these two worlds and bring tomography (and experimental analysis) into qutip.

For relevant papers, our most recent is on the arxiv: http://arxiv.org/abs/1407.6389 and earlier work can be found in PRA: Phys. Rev. A 63, 040101(R) (2001) and Phys. Rev. A 67, 032102 (2003)

Happy to chat more specifically if you are interested,

Best,

Andy

****************************************************
Andrew M.C. Dawes - Associate Professor
Pacific University Physics Department
2043 College Way, Forest Grove, OR 97116
Phone: 503-352-3171 Fax: 503-352-2933
Office: Price 107 - www.amcdawes.com
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[shahnawa...@gmail.com]

Hi,

I ended up here while searching if there were other QuTiP implementations for state reconstruction. Here are some super basic notebooks for the iterative Maximum Likelihood Estimation (https://github.com/quantshah/qst-cgan/tree/master/examples). I plan on making some more after my new preprint on this topic is out and make a #Tomography and Reconstruction# section in the QuTiP documentation. Scott, nice to see you here, I will have some interesting results soon on the arXiv for reconstructing optical quantum states and we can discuss more.

Best,

Shahnawaz