Making Optical Logic Gates using Interference 

I've always wondered about optical computing as well. Thanks very much for your video on the topic. Some ideas: I was recently reading about electrical memristors. Perhaps you could use photochromic materials as an optical memristor. I'm not sure if this would add an additional complexity or perhaps you could use photochromics without diffraction patterns to make a logic gate. Maybe also use polarization along the lines of "spintronics"? Looking forward to more!

Optical lock: little flash on one, nothing on two...

I've had this idea floating in my head for a while as well but had no idea how it would be executed. The optical lock idea is great and I loved the LPL reference.

"truly unpickable lock"... LPL: Hold my beer

The need for a Flip Flop is paramount for computing.

Nice presentation. Many current optical logic gates desings are based on the 'inteference' principle, for example those based on MZI. Phase delays are usually tuned by changing refractive index of materials or the length of light path. The diffractive method may have some advantages in computation (not necessarily logic gates since interference gives more than that). You may be interested in the following two papers:1.All-optical machine learning using diffractive deep neural networks and 2.Deep learning with coherent nanophotonic circuits. These two looks quite different, however both are based on interference.

That demonstration sweeping through the focal plane just blew my mind. I had no idea you could so precisely control the angle and phase of light with a 2D pattern. The ability to use lithography makes this very scalable and repeatable. I can see a lot of possibilities in stacking layers.

The questions you raise in your videos always stimulate fascinating ideas about QM.

2:27 Kudos for combining the right IC with the right schematic!

Absolutely brilliant! I love the intersection of ideas from theoretical physics and having the knowledge and equipment to conduct practical experiments. Great job on the video production both the content and visualizations are excellent! Channels like this one truly make me believe that we are in a gold age of citizen science. Keep up the great work!

I was theorizing and looking up how an optical transistor could work. Then I found your channel. Great video!

Just wanted to say, that analogue programming is an emerging field for machine learning. I am FAR from an expert, but I am sure that some data science firms would be happy to talk to you :p

Thank you sooooo much! I played with this effect about two years ago (used hair instead of those tiny patterns) and was totally amazed by how you can focus the light without a lense. The resources online are not too great on this topic so your video was a bliss for me :D

I am on my to a PhD on coherent combination of fiber channels and I was thinking about using the device for optical computation. Well keep you posted 😉

I've always had cursory knowledge about the specifics of how electronics work, especially in computing... I'm more of an artist. Although it helps when thinking outside of the box. The idea of photons instead of electrons has always intrigued me and has led me on a quest of understanding computing on a deeper level. Seeing you work on this is truly inspiring to see! Keep going!

Okay....this is awesome. I'm excited to see the first optical flip flop

You earned my subscription with this video, this is so exciting to see such a creative approach.

Super impressed! A couple of things come to mind: 1) the multi-lobed outputs 12:36 reminded me of QAM (Quadrature Amplitude Modulation) lobes. 2) the diagram in the lower right corner at 4:03 reminded me of the averaging functions of artificial logic processors. I think you're onto something brilliant! Good Luck!

Huygens Optics THIS IDEAS AWESOME

Only recently discovered this channel (thanks to the double slit experiment video), just finished watching everything you have here. Liked it very much! Maybe i'll go sort through my tiny box of salvaged optics now...

Fantastic work! Very nice explanations and video quality! Looking forward to the next one :)

Absolutely fascinating. I'd love to see more about this, especially if it's possible to "chain" multiple of these gates in series. For instance, It'd be great to see a basic adder constructed in this way.

What a fascinating video. Thank you so much for sharing your studies in this format!

It's been my long interest in trying to understand the concept of OPTICAL SIGNAL PROCESSING, which you speak and explain so marvelously. The ability to construct and implement it in real world-physical fabrication and use, sets my highest respect for your knowledge and tenacity to construct when others, white paper simulate. You are the bomb. The days of AT&T's Bell Lab research in optical / photonic / light wave for which journals I marveled, generated all this time asking and waiting ... "why is it taking so long to replace electronics". I now struggle in taking my unscientific knowledge, but having tremendous desire to proactively offset the financial pain from the rising cost and future decreased availability of secured energy- and design its practical use. ..You present the realism for someone like myself to attempt and implement its use for the common good. Thank You

I loved the reference to the lock picking lawyer :)

I know what I will do when I studied physics (another life) and am in my pension. The same thing you do, this is super interesting, I'm glad I subbed, you're brilliant IMHO

This is incredible. I'm familiar with digital logic, but these types of optics are beyond my level of education. I've always wondered how optical computing would work.

Fantastic! I heard Apple or IBM was working on an optical computer several decades ago, but never heard anything more about it.

Very nice work. I had a related idea a while back to "compute" by convolution at the Fournier plane. You might find some happy rabbit holes to go down with this method. Basically compute the fwd FFT of the logic you wish to impart, and then etch that as a mask.

this was recommended to me. Its incredible. Also i wanna see you partnering with some metal worker on yt to make that lock a reality to finally defeat LPL

I have always had it in my head that we should be able to implement logical operations with photons, nice to see it actually come to fruition.

7:40 wow your idea of putting 3rd Beam for interference are awesome .

This is amazing! This is something I’ve been theorizing my self and I love what you have here! Your validating my theories!

The unpickable optical lock looks like a worthy challenge for everyone's favorite lockpicking lawyer.

These experiments are perfect! Congratulations!

Fantastic video. I see a green sort of focal point when my eyes are closed.

0:32 Wow, just the other day i gave this explanation to my mom, but soon after i realized that the light can't cancel into nothing. I can't believe i haven't thought of that before. I didn't take the time to look up a better explanation though, so catching it here is pretty nice.

hahaha took me a while before i understood the LPL shoutout, very nice

Recently thought of this idea, which is how I found your video! Awesome! Thank you!!!

9:46 blew my mind. Just found your channel. Amazing stuff!

Destructive interference places the light somewhere else. How important those words are. First year physics teaches that photons cancel each other out, or it did in my day. Thanks for saying it, even if I change around your exact quote.

This is really cool. You need to find a way to get rid of any frequency / phase shifts introduced by the "light logic gate" itself, this is the holy grail. Because then you can build bigger blocks without the need for massive error correction.

I've thought about optical logic using optical ring resonators a lot since I saw a presentation at a RISC-V conference a few years ago. Ring resonators seem to be pretty trivial quantum devices because their boundaries are easy to understand, leading to interesting yet comprehensible topologies. Anyway, every time you release a video, I hope that you talk about photon sieves again and lead into clever applications for computation. Thanks for the interesting video in the meantime!

Awesome channel. I stumbled upon it by accident, but happy that it showed up in my feed

*@Huygens Optics* 12:41 What happens if you make this a spiral instead? Each revolution it goes 1 "band" (white to white) outwards. It changes thickness according to whatever the thickness you use at any radius here.

Very cool!

Very exciting work, having watched the earlier elements you presented I was left wondering where your mad genius was leading ;) Wishing you the best of luck and may the photons be kind to your research.

Great work. Clear explanation. I always enjoy a lot watching your video.thanks sir!

Interesting idea. I’m imagining a glass cubed cpu with optical fiber inputs and outputs. I think we will be using light for general computing sometime in my lifetime. It’s getting too expensive to make the latest processors using semiconductors.

Very interesting idea using interference, but I still can see how size might be a problem.

Wow that's probably the coolest thing I've seen for a long time

The problem is that light is (generally) linear. You could talk about these as individual gates, but if you actually connect them together, no matter what you do the final result will be a linear combination of what you started with. You can't get complex logic. Not unless you add something to make it nonlinear, like having a light sensor that triggers a laser. There are ways to do that, but I think that's the interesting part of the problem that needs to be focused on. Not something you can just ignore.

That lock idea is brilliant. I'm sure LPL would have a great time

You should try to create an optical transistor, where the input doesn't come from the other sources but a third that controls them. And maybe a two sided device that makes the light go back and forth.

This concept was part of my graduate work in the mid-1990's. A journal article in Applied Optics was published entitled, "Programmable optical logic systems using free-space optical interconnections."

Oh my! You, Sir took me back in 1995 when I have envisioned a similar approach! I have a Word document in an old hard drive somewhere! If I find it I will send it to you!

Fascinating video..is there anyone who dosent watch LPL ?

I wonder if there would be any benefit in trying to make zone plates with smoothly varying sinusoidal opacity, instead of the usual fully opaque and fully transparent stripes. I don't know how small you can get your details with your lithography setup, pretty small it seems, :) but perhaps you could use a sub-wavelength dither or sawtooth to transition between opaque stripes and transparent stripes. If I recall, moth's eyes do something similar to this, but in three dimensions. Their eye lenses don't have smooth glass-like surfaces, but rather the surfaces are blanketed with an array of sub-wavlength cones at sub-wavlength spacing, which the longer wavelength light treats as a gradual transition from the refractive index of air to the refractive index of the denser eye material. This gradual transition helps reduce the loss of light to specular reflection, making the moth's eyes more efficient. In the case of zone plates, you'd be creating a similar effect in the 2D zone pattern, by incorporating a sub-wavelength drop-off pattern in the opaque material as you transition out of opaque stripes into transparent stripes. If you could get the effective opacity to vary sinusoidally, then you'd have a zone plate that behaved much more like the pair of touching glass blocks you showed at 0:15, in terms of smoothly varying transmission and reflection stripes. This sinusoidal zone plate pattern might also help reduce the higher order additional focal points. Anyway, just a thought. Fantastic channel by the way. :)

This is my new favorite science channel. Well, I mean aside from Ben's Applied Science over here :P Seriously though, I love it man. Thanks for the fascinating and mind-juicing content.

this looks like some fun experimental technology, I would like to try this out.

I remember years ago pulling apart a cleverly engineered optical keyboard, it had a row of lights going down channels to led detectors at the other end. Each key had plate that would interrupt the light channels thus producing the ASCII character code for the key pressed. So you could implement a full optical computing system from input to logic and then work on optical output- wouldn’t that be cool.

Have you explored polarization as the logic level as opposed to interference based intensity?

TL;DR: Ordinary optical components are linear, and no combination of linear components can produce a non-linear device. XOR is non-linear. Optics is a wonderful field, and your craft and hand-on demonstrations are very beautiful, and a pleasure to watch. I certainly am not writing this to criticize you in any way, but merely to point out some fundamental considerations to be aware of. Ordinary optics (meaning a fixed arrangement of lenses, mirrors, diffraction gratings, filters etc) is *linear* in the sense that if an electromagnetic wave "A" at the input produces the output "X", and an input "B" produces the output "Y", then any mixture of A+B at the input produces a corresponding mixture of X+Y at the output. A Fourier transform is a linear operation, which satisfies the above property. Hence, it can be realized by an ordinary optical system. (Any other weighted sum or difference of inputs can also be realized.) But a lot of interesting computation is *not* linear or reversible. XOR is already very nonlinear! Threshold that is inherent in all of the ordinary electronic logic gates, even in inverters, is a non-linear transformation. Obviously, multiplication and division are non-linear, etc, etc. Finding roots of a quadratic equation is non-linear. Almost any computer program is extremely non-linear. In general, universal computation fundamentally cannot be realized with just the linear elements (the ordinary optical components.) To make a universal computer, one would have to add non-linear optical elements into the system. Such nonlinear optical elements do exist and are used occasionally to great effect (frequency doubling, for example, like in green laser pointers), but as of yet there is no easy to use, inexpensive non-linear optical element that would be equivalent to a transistor. With the ordinary linear optics, you can make a linear mixture of the inputs that resembles some logic operations. But without sneaking in some non-linear operation, no matter how you cascade these linear blocks, the result will always remain a linear system, and some even very simple things like XOR will not be even approximately realizable. There are of course great many other things that only optics can do. Good luck with your experiments -- love your work!

so cool! when i heard about all the strange non-linear optical effects certain materials had I got straight to thinking how they could be used to build gates. w/ Raman amplification and cross-phase modulation, you can basically build all-optical transistors. optical phase conjugation just blows my mind.

it's going to be very hard to chain these gates, considering each of them outputs light in a different polarization state depending on its inputs.

The idea of a adding a third always-on beam is ingenious. It's also absolutely necessary for creating a NOT, otherwise there would be no light for a "0" source. :)

This is such a fascinating concept. I have imagined optical computers based on hexagonal crystals with the optical operators on the hexagonal faces and the data on the end faces with the output data being through an optic fibre cable for conversion to standard electronic function elsewhere. There are so many fabulous mechanisms such as using air (vacuum) gaps to allow past data to jump ahead of current data, optically clear piezo electric crystals to deflect beam direction, and photonics devices are beginning to appear. The prospect is to build fast computers that are immune to EMPs, but also have indefinite life to store the history of our civilization beyond its inevitable collapse. Keep going, this is huge.

You are certainly onto something here. The Canadian company Xanadu quantum is working on a similar way to use integrated optics for quantum computing.

that was an unexpected lockpicking lawyer referance

How do you plan on normalizing outputs again so you can use multiple gates in series?

add sensors at both destructive and constructive points to give a ratio output, use log amps to help digitize, allows more precision over a much larger bandwidth of light level variations. etch the outer ring of interference filters on the other side of the glass to get back your genius win. make the thickness correct for height delta to re-align focal points in space. poppa was a photon magician, learned this stuff in the back seat of a station wagon. great videos. your tesla valves can be used to generate water level differences. This can be used to measure flow direction and pressure differentials with fluid induced optical path changes. This can be used as a logic device for flow control and measurement

I remember a family friend who worked at Lucent telling me that they were working on a fiberoptic network switch that would direct the flow of traffic without media conversion. No copper. I wasn't able to tease an explanation out of him (that I could understand, dunno why was telling a kid my age something like that anyway) and I've wondered about it once or twice a year ever since. I think I've finally got an answer to that question that I understand, thanks.

Need a way to amplify the signal without using CCDs and LEDs. Logic gates aren't just switches, they also amplify the signal to keep the fan-out.

Отлично!!!

A memristor might have useful analogues in the passive resonant filter domain. If you picture a broadband noise signal passing through a classical filter, its resonant/dampening footprint is visible on the output spectrum like an equalizer output. If you can close the loop by controlling a passive filter to make its static parameters quickly adjustable , it could selectively alter a spectrum passing through it, suggesting one stage of a parallel processing pipeline. The advantage is the accumulated results of accuracy over time are like the shutter speed trade-off in photography. The more exposure the less noise, up to a point. Such a system would use frequencies to represent state, with interference providing a means of active logic. Because a spectrum contains multiple frequencies, it could perform multiple analog or logical operations in one pass. Critical design decisions include how to move data into the frequency domain, and how to make use of interference, and how to read the state out from the system, and there are a few possible paths and maybe new approaches yet to unfold as well. I like your research angle, perhaps you are going to introduce how you will change the masks dynamically to afford speedy input on the optical comparators. Perhaps you will find a speedy transducer array that can control a grid of pinholes? Or use the Digital Light Projector somehow in this role. Just wondering what’s next. Beautiful work all around, cheers.

I think "why i make a basic calculator worked by colors" and you appeared before me... its unbelievable think mate its very cool. And homemade CPU, its fantastic!!

Interesting, I've been tooling around with the idea in my head for a while. Should be a good video. =) Edit: Ok finished the video. This is similar to what I was thinking. My idea was based upon the double slit experiment and you'd basically fire two beams of photons (one beam per slit) and if both were on, you'd get photons in the center of the diffraction pattern at the "aperture", so basically an AND gate. I hadn't really worked out the NOT gate yet but once that was figured out you could build a NAND gate and then from there since its a universal gate you could build any of the other logic functions; OR, XOR, etc.. and well... things just progress from there. Sure since everything is NAND the gate count goes up, but given the speed at which it would run, I don't think one would care until you're pushing the limits of the technology. One concern if chaining gates along to form logic and computational units is the attenuation of the light going from one gate to the next. Since the light is diffracting I would suspect some photonic loss at the aperture. So at some point you'd need a signal booster of some sort. This was one of those things where I figured if I had thought of it surely someone somewhere else much smarter than I had already thought it through and determined it wasn't viable and hence why we don't currently have the technology. =) But hey, maybe there's something to it after all? It's certainly interesting stuff.

is the exclusiv or gate not called XOR? i never heared of EOR

I was also come up with a very similar implementation for the optical logic circuits few years from now, it's very nice to see it practical implementation.

Awesome video, the concept and execution shows that this idea could be further developed (and maybe miniaturized). That would give a whole new meaning for optical devices

It looks like a shitload of energy is being lost on each gate.

love the lock picking lawyer reference

Wonderful demonstration and explanation! If you consider polarization as well in to it, you will get more bits in the gate!

I'm currently working on running simulations for optical neural net components. Good to see more people are considering the potential in integrated photonics. I don't know if interference is the right strategy though considering the difficulty of getting interference on chip with enough nodes.

0:46 The explanation actually makes perfect sense. Destructive interference does not destroy the EM energy, but two waves of equal amplitude and opposite phase will not have an effect on the rods or cones in your eyes, or a light sensor in a camera. Both rays of light still reach their destination but cannot have an effect because of their evil twin.

The only gate you actually need to be able to make is the nand gate. All others can be built from that.

Congratulations on your work, I'm an engineer and I always imagined we'd have optical logic ports someday. Now I see that Chinese are already developing optical computers. I really enjoyed your work congratulations. That's the future

Pure optical switches, and LCDs/LEDs where my first thought on the topic of optical interference

As I'm sure you're aware, all logic gates can be built by series of XOR gates or XAND gates. So if you can produce a very simple and reliable XOR, you have everything you need to build arbitrary microprocessors!

Making more logic gates in the same area as we currently have and power them with UV/Vis light will be really hard.

This is insanely cool

I am a EE from U.C.Berkeley. This is quite interesting. Will research this more.

I remember designing something back in the 90s that required an LED to flash 10,000 times per second, and I ran into the problem that the LED would remain glowing for many microseconds after it was no longer powered. (Maybe LED technology has moved on.)

Oh man! Please make a full episode extending from 2:15. Plz!

Computing and graphics decoding at the speed of light. Photonics. Great 👍👍👍😊

Another way to create the gate, is to create a laser crystal whose electrons are excited by one input beam, while the 2nd beam causes the electrons to stabilize and produce a known wavelength that is emitted. The implementation is a bit more complex, but has a higher degree of working.

LPL: Now although this lock would deter even the most experienced of pickers, it is vulnerable to a very simple attack. That is, the strobe light.

Here someone who developed this technology to the next level, and claims "Beating Moore's Law: This photonic computer is 10X faster than NVIDIA GPUs using 90% less energy", the company is called lightmatter.

Great video! An un-picable lock. Brilliant. You should file for a patent on that if you are the first, or at least write a whitepaper and have it published - even on RU-vid if no one will pick it up. Optical computers, this is very stimulating (no pun intended). If you could do this with individual photons, quantum computing may merge with this. For those of you not familiar with digital logic gates: In electronics, all you really need is NAND gates because a 2nd NAND gate (with one input tied to a logic '1') on the output of the first acts as a NOT (inverter) gate and converts the NAND gate to an AND gate. So, using NAND gates, you can make: NAND, NOT, AND, OR, NOR, EXCUSIVE OR, EXCLUSIVE NOR, and any other gate with various combinations NOT on the inputs and output... and you have ALL the building blocks of computer logic. With Optical Logic, you start OR and NOT gates, and those too can be combined in various ways to create ALL of the same building blocks gates used in electronics. For example: Demorgan's Therom states you can convert, say an OR gate to an AND gate by putting a NOT on each input and output of the OR gate. Try it: The truth table of a Negitive Logic OR gate (one with NOT on the all the inputs and output) and truth table of an AND gate, both tables give the same results with respect to their inputs (thus the same gate, just inverted "logic/polarity" symbols). A postive logic AND gate is the same as a Negative logic OR gate, they do the same but you look at the logic from positive or negative perspectives, so the symbols are different but do effectively the same.

Thanks for posting bro! It's really cool...