by radioactivist on 7/22/20, 2:24 AM
While this is a nice demonstration of the polarization of light, this is not a demonstration of quantum mechanics, or quantum computing (though it does have pedagogical value, if qualified properly).
Polarizers essentially just project the electric field of the wave onto some axis, zeroing out the perpendicular component. Keeping in mind that light intensity is the square of the electric field strength, all of this can be explained through straightforward classical electrodynamics.
An analogous statement would be that interference of light (say through a pair of slits) is also quantum mechanical in nature. This isn't strictly wrong (since basically everything is quantum mechanical in nature when you get down to it) but is a misleading way to present something that can (and was) understood perfectly well before quantum mechanics came along.
Note: These kind of experiments for a single particle (e.g. photons, electrons, etc) are a different story and do provide a demonstration of quantum mechanics (and the combination of wave-like and particle-like properties intrinsic to it).
by sasaf5 on 7/22/20, 5:07 AM
This is a real-valued computer, not a quantum computer. In the described algorithm the state is the real-valued angle of the polarizer. One could very well implement this algorithm using the charge on a capacitor. Also the algorithm has bugs, it can overshoot the vertical. The author does acknowledge these shortcomings in the "caveats" section. But with all those caveats, you are not building a quantum computer at home.
by ThePhysicist on 7/22/20, 8:18 AM
Nice article, but not really a quantum computer or even a system that needs quantum mechanics to explain it. You could do the same calculation with an analog system (e.g. a capacitor that you add/remove charges to/from). The argument from Scott Aaronson about quantum advantage that the author refers to is really not very relevant, as a single qubit doesn't have any information encoding advantage over an analog system. A quantum computer simply cannot produce a speed advantage without relying on entanglement at some point during the quantum computation. So: no entanglement = no speed advantage.
by dhruvp on 7/22/20, 1:53 AM
Hi! Author here - If you have any feedback on what can improve please let me know! Thanks for reading and feel free to shoot me a note at dhruv.parthasarathy@gmail.com if you'd like to see something edited.
by snowwrestler on 7/22/20, 4:00 AM
The 3-polarizer experiment is a very cool way to demonstrate the weirdness of light.
And the idea of using sequential rotation to keep track of cumulative bias in coin flips is an interesting concept.
But ultimately I think neither one of those concepts really depends on the other in this experiment. Checking for light through polarizers is neat, but keeping track of any other rotating macro-scale object would work just as well. You can do the same thing by rotating a stick on a piece of graph paper. If it goes beyond your pre-determined test angle, you declare a bias.
As I understand it, the crazy thing about quantum computing is that you don't need to go sequentially; you can simultaneously compute every test flip in one step with qubits. That's why quantum computing could speed up certain calculations. (Note: please don't ask me to explain how.)
by frequentnapper on 7/22/20, 2:11 AM
maybe i'm missing something here, but could we not have just used a stick on the ground and rotated it accordingly, and still end up with the same result - if the stick ends up perpendicular to the plane, i.e. you? Why do we need the light polarization setup?
by keyle on 7/22/20, 2:14 AM
It's more of a quantum demonstration than a computer, no?
by srajap06 on 7/22/20, 3:42 AM
Analogous statement would be that interference of light (say through a pair of slits) is also quantum mechanical in nature. This isn't strictly wrong (since basically everything is quantum mechanical in nature when you get down to it) but is a misleading way to present something that can (and was) understood perfectly well before quantum mechanics came along Thatis.
by thdrdt on 7/22/20, 8:51 AM
Is it possible / are there virtual or emulated quantum computers?
I read about the Kyndi model but could not find any implementation.
by abhayhegde on 7/22/20, 1:38 PM
I liked the article, but this is not a quantum computer. Please do not take away the credibility of what a real quantum computer could achieve. This is at best an algorithm to reveal the angle of polarizer, and also the nature of light.
Although, appreciate the efforts.
by hetman on 7/22/20, 3:04 AM
Not sure what's up, but this website refuses to scroll on any Chrome based browser on my phone. Works fine in Firefox though.
Edit: Weird. Now it works. Though there still some initial "resistance" when I start scrolling...
by imvetri on 7/22/20, 9:26 AM
I like it.
by starpilot on 7/22/20, 3:07 AM
Has anyone cracked SHA with this?