Quirk

Cool they made a custom edition of a quantum circuit simulator that introduces concepts one by one. It's based on this general purpose QC simulator https://github.com/Strilanc/Quirk#examples (check the animated gif demo; very powerful stuff) Lol... with V8 and SpiderMonkey getting faster and faster, quantum computing simulations in js are probably as powerful as anything that can be done in a lab these days ;)

The github repo: https://github.com/Strilanc/Quirk The blog post introducing it, with a bit more context: http://algorithmicassertions.com/2016/05/22/quirk.html

Yes, that's one of the things I plan to do [1]. (You can copy individual gate parts by holding shift as you grab them. I'm considering adding ctrl as a another modifier, meaning 'grab the whole column'. I understand that these modifiers are not discoverable.) (At the moment, when I want to make a really large repetitive circuit, I copy the URL into a text editor and do my copy pasting there. I understand that it would be totally ridiculous to expect users to do that.) 1: https://github.com/Strilanc/Quirk/issues/148

Yeah, using the GPU makes a huge difference. It's also incredibly finicky because the hardware and browser support varies so much. Basically I represent an n-qubit superposition as a 2^(n/2) x 2^(n/2) texture with each pixel being an amplitude (with red=real, blue=imaginary components). Then I use fragment shaders to operate on all the pixels in parallel when applying a gate. For example, here's the GLSL in the main method of the "UniversalNot" gate's shader [1]: vec2 xy = gl_FragCoord.xy - vec2(0.5, 0.5); float state = xy.y * outputWidth + xy.x; float hasBit = mod(floor(state / bit), 2.0); float partnerState = state + bit * (1.0 - 2.0 * hasBit); vec2 uv = uvFor(state); vec2 partnerUv = uvFor(partnerState); float control = texture2D(controlTexture, uv).x; vec2 val = vec4(texture2D(inputTexture, uv)).xy;

I have my own shameless plug to add. Another drag-and-drop quantum circuit simulator that runs in your browser is "Quirk" [0]. Quirk is faster than Davy's simulator thanks to webgl. It calculates varying operations on up to 16 qubits in real time as you drag gates around. It also lets you drop inline state displays into the circuit. Plus you can link to circuits, though the links can be a bit long so you may want to do so indirectly [1]. That being said, Quirk lacks the ability to compile circuits into a gate. Also it doesn't have a QFT gate (yet). I'm working on it. [2]. 0: http://algorithmicassertions.com/quirk 1: https://t.co/qi12H3aVU1 (6-qubit grover circuit with displays, near the getting-laggy limit in terms of op-count) 2: https://github.com/Strilanc/Quirk