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Stanford engineers' breakthrough heralds super-efficient light-based computers
- ses4j 11y agoThe topic is fascinating, but the article doesn't talk to how this "reverse design" algorithm works at all, which I think might be very relevant to this audience. Does anyone have a link to more about the design algorithm and how it works?
- phkahler 11y agoTFA includes a link, but the paper is behind a paywall at Nature.
- dxbydt 11y agoStupid nature paywall honestly makes me furious. Why doesn't altman or some other yc partner throw some money at nature & get all their articles up on the web for free ? /endrant
- Someone 11y agoThe 'real' paper sits behind a paywall at http://www.nature.com/nphoton/journal/v9/n6/full/nphoton.2015.69.html http://www.nature.com/nphoton/journal/v9/n6/full/nphoton.201..., but http://arxiv.org/pdf/1504.00095 http://arxiv.org/pdf/1504.00095 probably is fairly similar. Crux seems to be "our algorithm searches the full design space of fabricable devices with arbitrary topologies." Very useful, but may be not that spectacular, depending on the efficiency of that search.
- anewusername 11y agoAn arXiv preprint of the scientific article and copies of our previous work on this topic are available on our research group's website[1]. Just search the page for "design"; the most detailed reference would probably be Jesse Lu's thesis[2]. [1] http://web.stanford.edu/group/nqp/publications.shtml http://web.stanford.edu/group/nqp/publications.shtml [2] http://web.stanford.edu/group/nqp/jv_files/thesis/Jesse-thesis.pdf http://web.stanford.edu/group/nqp/jv_files/thesis/Jesse-thes...
- amelius 11y agoMy first guess would be that it combines a standard "black-box" technique for solving optimization problems (e.g. genetic algorithms, simulated annealing), with an electromagnetic simulation at each iteration. But that is just a wild guess :)
- fferen 11y agoI uploaded the paper for anyone interested: https://drive.google.com/file/d/0B2R-ri3N25FnWHBWRzNlak01WEE/view https://drive.google.com/file/d/0B2R-ri3N25FnWHBWRzNlak01WEE...
- dxbydt 11y agoActually approachable math - senior undergrad math major or first year grad can easily understand what's going on. ADMM is actually very old primal dual setup solved via Lagrangian, goes back to 1980s I think. Good reference - https://web.stanford.edu/~boyd/papers/pdf/admm_slides.pdf https://web.stanford.edu/~boyd/papers/pdf/admm_slides.pdf The article itself refers to Boyd's Convex Optimization textbook, which is sort of a rite of passage for anybody doing anything math-related at Stanford these days - even their MS in Management course requires a semester of convex optimization.
- marcosdumay 11y agoThe article talks about switching in a single place, as if by accident. The abstract has no mention of switches at all. Yet, "light-based computers" is something completely dependent on switches, and not much of anything else. If somebody has access to the actual paper, is there any chance that can lead to switches? Or just multiplexing / demultiplexing? Update: Thanks fferen. It did demuxing. No work related to switches, except for a "in the future, somebody may use a similar technique to make a switch" on the end (yeah, maybe, using some other dozen techniques not yet discovered, and this one). Demuxing is very important, just that it alone does not lead to practical photonics.
- anewusername 11y agoThe actual paper is about realization of an algorithmically-designed optical device rather than optical switching. The device is "just" a computer-designed multiplexer.
- infogulch 11y agoCould such a device alter the relative phase of two separate beams of light? This optical device would take as input two beams of light with some arbitrary phase difference, and output the same two beams but with their phases changed to some fixed offset relative to each other. With such a device an actual switch becomes easy: Make the device change the two inputs to be antiphase and combine them. If one of them is missing, the other passes through unphased (pun intended), but if both are present they cancel each other out; aka you have an xor switch!
- Strilanc 11y agoFirst, waves still pass through each other when destructively interfering. They temporarily cancel out each others' amplitudes, but not each others' change-in-amplitude, so they continue to propagate. Second, XOR is not a universal gate (even when combined with NOT). XOR can only sum things together (mod 2). For universal computation you need to be able to multiply (e.g. with an AND gate or a Toffoli gate).
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- tslug 11y agoIf it's using infrared light for signaling, doesn't that mean waste heat could more easily corrupt data?
- marcosdumay 11y agoThere are several different frequencies of infrared. Unless your chip is getting too hot (in the 400°C or more), the best frequencies do not mix with thermal radiation.
- bostik 11y agoDoes this sound like something out of Dirk Gently to anyone else? > Now the Stanford engineers believe they've broken that bottleneck by inventing what they call an inverse design algorithm. > It works as the name suggests: the engineers specify what they want the optical circuit to do, and the software provides the details of how to fabricate a silicon structure to perform the task. I'm quite sure the first novel, Holistic Detective Agency described a computer program that could do that. (In the novel it was of course sold to a governmental body, maybe military.)
- aristus 11y agoThe software took in the thing the user wanted to do as input, and made up plausible excuses for why it should be done. A rationalization engine, as it were. This is a bit different, more of a constraints optimization problem. If you want a really weird story about that, here's one about the evolved FPGA: http://archive.bcs.org/bulletin/jan98/leading.htm http://archive.bcs.org/bulletin/jan98/leading.htm
- duaneb 11y ago> A rationalization engine, as it were...This is a bit different, more of a constraints optimization problem. How is this any different? An argument from fulfilling constraints optimally is very, very rational.
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- Thimothy 11y agoWhat that article says is incredible, awesome and I wonder if I could replicate it. It probably uses some Xilinx proprietary info about the bitstream though.
- loarake 11y agoThis is actually what we do in radiotherapy nowadays, it's even called "inverse treatment planning". Basically a radio-oncologist or a dosimetrist contours (manually, with a pen) organs on every slice of a CT scan and then we just say "We want this much radiation in the tumour, and less than Y units in surrounding healthy tissues". Treatment planning software then simulates dose distributions from a bunch of possible radiation beam collimations and adjusts the amount of radiation coming out of each radiation "field" to minimize a cost function penalizing overdosing healthy tissue and underdosing the tumour(s).
- peter303 11y agoI heard similar "optical break" stories when I was at Stanford decades ago. i hope this could the one ;-)
- PhantomGremlin 11y agoHow does verbiage like this get written? The Stanford algorithm designs silicon structures so slender that more than 20 of them could sit side-by-side inside the diameter of a human hair. Who is their target audience? Just how innumerate do you have to be to prefer that text to some actual dimensions?
- anigbrowl 11y agoThe target audience is TV and print media. Watch, this will be on local Bay Area stations within 72 hours to fill 2.5 minutes of the evening broadcast. Most news is targeted at people with a 6th grade understanding of the world.
- mstresh 11y agoI did my PhD work in silicon photonics (in a different lab group and not associated with the authors in the paper) and thought I could chime in with some extra background and why this result is interesting to the silicon photonics community. First off, silicon photonics has already made its way into several products, mostly active optical cables (a device that directly converts an electrical signal to an optical signal). See, for example, Luxtera/Molex, Acacia, and Kotura/Mellanox. Additionally, many other companies have demoed interesting things at trade shows (e.g. Cisco, Intel, Fujitsu, and others). In general, the appeal of silicon photonics is that we can fabricate almost all of the components of an optical link on a single chip using the same fabrication tools as what you might find in a standard CMOS fab. Modulators, detectors, switches, filters, and other devices have been demonstrated on a single wafer. Many organizations (ePIXfab, IBM, IME A*STAR, Intel, Freescale, and others) have fabrication processes that have all of these devices right next to each other on a wafer and are capable of 25+ Gb/s data transmit and receive. Others in the comments have mentioned the lack of switches in the article. Making optical switches in silicon has been demonstrated before, usually with either a Mach-Zehnder interferometer or resonant structure. The phase of light or resonance are most commonly adjusted through the thermo-optic or plasma dispersion effect. I'm at work now, but I can dig up references if anyone is interested later. This result by Piggot, et. al., is most interesting because it is a unique device geometry for performing a wavelength splitting function. The performance of the device itself isn't particularly impressive relative to other devices with similar functionality that have already been demonstrated [1]. Additionally, the use of an MMI structure for wavelength multiplexing is also not novel [2]. So how does this relate to "light-based computers?" The vision that places like IBM research try to sell is that we will eventually integrate photonics (either monolithically, or flipped in some form) onto our processors and memory chips to enable high-throughput on- and off-chip I/O. This is still likely 10 years away from commercial products. Near-term, look for silicon photonics in your data centers and fiber-optic regional, metro, and long-haul networks. (FTTx one day, but silicon photonics currently can't compete in economics with a DML shoved into a TO can.) [1] See http://www.nature.com/lsa/journal/v1/n3/full/lsa20121a.html http://www.nature.com/lsa/journal/v1/n3/full/lsa20121a.html for a review article on silicon passive optical devices [2] http://dx.doi.org/10.1063/1.4812746 http://dx.doi.org/10.1063/1.4812746
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- smegel 11y agoHmm zero cases of the word "transistor" appears in the article. My skeptics hat is hovering above my head right now...
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