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Research
Last updated: February 19, 2007 @ 11:06pm
I have a wide variety of research interests. Currently, my main research for my Masters has been to build a Free-Space Quantum Key Distribution System which operates over the UW and PI campuses. But included here are also projects that I am interested in doing in the future and sometimes just topics that have piqued my interest. I have included links to more info on the topics that I have researched in a little more depth. I have also done a couple of projects in engineering throughout my undergraduate career and they are also included here.
Quantum Key Distribution is a provably secure way of distributing a secret shared random bit string (a secure key) between two parties Alice and Bob. What makes QKD important is that all of the current classical encryption technologies are predicated on the assumption that certain mathematical problems are "hard" (ex. factoring large numbers quickly in the RSA algorithm). Already classical cryptography is in trouble because algorithms to factor large numbers quickly are already known for a quantum computer. Thus, as soon as a quantum computer of appreciable size is built, all of the cryptography currently in use will become insecure. However, for QKD it is the laws of quantum mechanics which prohibit an eavesdropper from learning about a key without being detected. Thus, it is the laws of quantum mechanics guaranteeing security rather then the unproved mathematical "hardness" of certain problems. So I have developed a free-space (sends photon pairs through the air between sender and receiver telescopes) quantum key distribution system. Click on the more details link for a more complete description of the project.
A Hybrid Telecom - Free-Space Quantum Key Distribution System | More Details
I've been talking for a little while now with Josh Slater of the Institute for Quantum Information Science (IQIS) at the University of Calgary and Félix Bussières of the Départment de Génie Physique at the Université de Montréal about collaborating (through the QuantumWorks network) and putting together a hybrid telecom - free-space quantum key distribution system at most likely the University of Calgary. Félix and Josh have been doing a lot of research on a source of entangled photon pairs with one at ~800nm and one at ~1550nm. The idea would be that I'd lend my skills with the free-space optics and take some of my stuff to Calgary so that we could set up one ~20km fibre link (which I believe is already installed) and one free-space link (with the equipment that I brought). Would be a neat collaboration, and I'm hoping that it'll happen this Winter 2008 or Spring 2008. I'll put more paper links on here about the various components of the potential system when I have time.
Machine Learning in a Quantum World
So I saw a presentation by Sebastien Gambs, a PhD student of Gilles Brassard and Esma Aimeur, at The 3rd Annual Canadian Quantum Information Students Confernce at The Institute for Quantum Information Science (IQIS) at The University of Calgary in August 2006. Sebastien talked about uniting the Machine Learning and Quantum Information realms and it really sparked my interest. Admittedly though, all I have had time to do is read a single paper that Sebastien has sent me. But I am hoping to get into the subject soon. It looks like quite an exciting and very new subject with lots of oppourtunity to do some good work in. For anyone else interested in this, I would suggest talking to Sebastien as a good starting point.
Envariance
This is based on a couple of papers (Environment-Assisted Invariance, Entanglement, and Probabilities in Quantum Physics, Probabilities from Entanglement, Borns Rule from Envariance) by Wojciech Zurek. The basic gyst of this, as far as I can gather, is that by looking at the invariance of say the bell state |psi-> = |HV> - |VH> under spatially separated local unitary transformations, you can derive the Born Rule of Quantum Mechanics. All it requires to experimentally verify this is an entangled photon source, which I have already built for the QKD system. So I might as well provide some experimental verification for the paper. Right now, it is on the back burner for a little bit, because I will probably have to put in some sharper filters to improve the entanglement and wavelength indiscernibility of the source.
A Test of the Local Causality of Spacetime
*** So unfortunately this looks kind of defunct in terms of whether I'm going to do it or not. Not only would it be a large undertaking, it appears that Gisin's group is actively trying to do it. And since I don't have the resources to compete with his group, and the technology to do the really cool version of this experiment (measuring the changing gravitational field directly), I'm going to focus my efforts on other experiments. Ah well :P ***
This is something I have actually become quite excited about. The PhD student, Rolf Horn, next to me just started bugging me about it in February. We went to a Conference in Honour of Abner Shimony at the Perimeter Institute in July 2006. One of the presenters at the conference was Adrian Kent who presented the talk A Proposed Test of the Local Causality of Spacetime. He talked about entangling two spatially separated macroscopic objects, thus violating the local causality of spacetime (a property of general relativity). At first glance, I thought the experiment was trivial (and in principle done by my supervisor Gregor Weihs in the paper the Violation of Bells Inequality under Strict Einstein Locality Conditions) since there has been tons of experimental bell inequality violations done. But upon thinking about it a little more, I have become convinced that it is a worthwhile experiment to do. It will require a little thought to add a piezoelectric crystal of some sort (an idea due I think to Nicolas Gisin, though I am still looking for a reference) attached to the two QKD detectors so that it deflects in a different direction depending on the polarization of the photon measured. The piezoelectric crystal will provide a macroscopic deformation of the local spacetime metric. Now I belive (as the majority of people I think do) that nothing special is going to happen, and we will measure a bell inequality violation, just as before. But even this would have some worth, since it would show strikingly that General Relativity is not the whole story (and convince some die hards in the relativity community). But you never know, maybe when you got outside the light cone separating the two measurement events, you would measure a Bell parameter around the classical value of 2. Weirder things have happened, and this would definitely cause some ripples in the scientific community. In any event, I am hoping to do this with my QKD system sometime this summer 2007. I would like to carry on with a further variation of the experiment as well afterwards.
For my fourth year project in Systems Design Engineering my group (myself, Simon Lai, and Keon Choi) worked with Jean Christian Boileau, a graduate student at the IQC. Jean Christian (along with Martin Laforest, Casey Myers, and Raymond Laflamme) wrote a paper Robust Quantum Communication Using a Polarization-Entangled Photon Pair detailing a protocol which allows one to overcome the decoherence induced by the birefringence in optical fibres on qubits encoded in photon polarization. Their paper left open the possibility of improving the protocol using active feedback. Now, I did the project when quantum computing was still new to me, so our project title was certainly a little naive now that I have learned a little bit about the vast subject of Quantum Error Correction. Since this project did not have anything to do with Quantum Error Correction, a better title for the project would probably have been something like "Optimizing the Birefringence Induced Decoherence of Polarization Qubits in a Optical Fibre using Classical Feedback". In any event, whether the actual feedback stuff was worthwhile or not, we did do some decent simulation work. You can click on the more details link to find out more about the project.
This was a project for my 3B engineering design course. My group and I found Prof. Jack Callaghan, a professor in Kinesiology, who researched the effects of cumulative loading on the back. Researchers typically relied on video analysis and contrived laboratory situations to gather data. Prof. Callaghan was interested in having us develop a system that could automatically measure the force being exerted on the hands and save it to a database. So we developed the PALM (Pressure Area Load Measurement) prototype system to accomplish this goal. Click on the more details link to find out more about the project.
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