The trick of quantum computing is to take the advantage of wave mechanics (superposition) and entanglement. This allows to perform parallel computations/manipulations with $2^n$ superposed waves for $n$ bits. This principle does not rely on quantum mechanics. Superposed waves do also exist in classical mechanics (although I am not sure we can make the number of tones also scale exponentially with the size, but there could be some profit). Are there examples of efforts to create classic analogues of quantum computers that use superposed waves and manipulate those, instead of using bits in silicon chips? (I do not mean efforts to create a virtual quantum computer) This question might be generalized. Are/were there any efforts to try to move away from binary computers?
The intuition I have for why quantum computing can perform better than classical computing is that the wavelike nature of wavefunctions allow you to interfere multiple states of information with a single operation, which theoretically could allow for exponential speedup.   But if it really is just constructive interference of complicated states, why not just perform this interference with classical waves?  And on that matter, if the figure-of-merit is simply how few steps something can be calculated in, why not start with a complicated dynamical system that has the desired computation embedded in it. (ie, why not just create "analog simulators" for specific problems?)
Proof that the real numbers are countable: Help with why this is wrong Drush PHP syntax error when running I am following the instructions to install Drush that are listed on this page:   I seem to be getting a syntax error within the code:  [user@localhost ~]$ wget https://github.com/drush-ops/drush/releases/download/8.0.0-rc4/drush.phar --2015-11-16 16:23:02--  https://github.com/drush-ops/drush/releases/download/8.0.0-rc4/drush.phar Resolving github.com (github.com)... 192.30.252.131 Connecting to github.com (github.com)|192.30.252.131|:443... connected. HTTP request sent, awaiting response... 302 Found 2015-11-16 16:23:05 (1.47 MB/s) - drush.phar saved [3496991/3496991]  [user@localhost ~]$ php drush.phar core-status  Parse error: syntax error, unexpected '[' in phar:///home/user/drush.phar/includes/output.inc on line 188   I am not seeing this error on Google. Any idea how to fix it? Displaying equations, how to combine strings and values without evaluating everything. This is an idea I have seen around, but I have not seen a feature request for it, so here it is.  Downvotes that have no comments are frustrating and difficult to manage.  This is a way to help improve that:   Have a downvote initially cost more to cast for the downvoter (5 points for example) When a comment (from the downvoter) on the downvoted question/answer gets an upvote, you get your points back.   All points (ie all 5) could be refunded or just up till the traditional -1 that is in place now (ie 4 points refunded).    This would encourage good comments and downvotes for real reasons.  (Because comments for questions/answers that are bias related will not get the upvotes as readily.)  This could/should be limited to non-subjective tags.  (ie tags where a downvote just because you "don't like it" is not appropriate.) Print escaped representation of a str What is the difference between N and N-1 in calculating population variance? I did not get the why there are N and N-1 while calculating population variance. When we use N and when we use N-1?      It says that when population is very big there is no difference between N and N-1 but it does not tell why is there N-1 at the beginning.  Edit: Please don't confuse with n and n-1 which are used in estimating.  Edit2: I'm not talking about population estimation. If photons have no mass, how can they have momentum? As an explanation of why a large gravitational field (such as a black hole) can bend light, I have heard that light has momentum. This is given as a solution to the problem of only massive objects being affected by gravity. However, momentum is the product of mass and velocity, so, by this definition, massless photons cannot have momentum.  How can photons have momentum?   How is this momentum defined (equations)? Share menu hangs iOS app The Share menu in iOS 13 got a redesign, and the Stack Exchange iOS app is no longer compatible with it. I can still use it to copy the link, but when I try close the menu, it remains stuck. Opening another app and then returning automatically dismisses the menu, but then I can't use the back button anymore to return to the question list. (I'm still able to refresh the page, so it's a navigation issue.)    Ironically, I discovered this bug while trying to mark  as a duplicate; in the app, the quickest way to do that is to use the Share menu to copy the link to the original question to the clipboard...   App Version: 1.6.6.2 Device: iPhone 7 Plus OS Version: Version 13.1 (Build 17A844) How to deal with perfect separation in logistic regression? If you have a variable which perfectly separates zeroes and ones in target variable, R will yield the following "perfect or quasi perfect separation" warning message:  Warning message: glm.fit: fitted probabilities numerically 0 or 1 occurred    We still get the model but the coefficient estimates are inflated.   How do you deal with this in practice? Let $\alpha, \beta \in \mathbb{C}$, such that $\alpha + \beta$, and $\alpha\beta$ are algebraic. Show that $\alpha$ and $\beta$ are algebraic. Let $\alpha, \beta \in \mathbb{C}$,  such that $\alpha + \beta$, and $\alpha\beta$ are algebraic. Show that $\alpha$ and $\beta$ are algebraic.   attempt: Suppose $\alpha, \beta \in \mathbb{C}$ such that $\alpha + \beta$, and $\alpha\beta$ are algebraic.  Let $\alpha + \beta$, $\alpha\beta$ are algebraic be algebraic over $F$. And let $\alpha, \beta \in K$, where $K$ is an extension of $F$.  then $\alpha + \beta $ and $\alpha\beta$ lie in the extension $K = F(\alpha,\beta)$, which is finite over $F$.  so $[F(\alpha, \beta) : F] = [F(\alpha, \beta): F(\alpha + \beta, \alpha\beta)][F(\alpha + \beta, \alpha\beta) : F] \leq 2[F(\alpha + \beta, \alpha \beta) : F] $, since $\alpha + \beta$ and $\alpha \beta$ are roots .   So $[F(\alpha + \beta) : F]$ is finite and in the extension $F(\alpha,\beta)/F$ the elements must be algebraic over $F$, then $\alpha , \beta$ are algebraic.  Can someone please verify this? Or help me give a better approach. Thank you! Why are only certain shutter speeds or apertures available? For the exposure control function DSLRs there are specific shutter speeds available. For example there are 1/4, 1/100, 1/500. Why, even in high end DSLRs, is there no option to use a custom shutter speed (such as 1/19)?   If the camera can do 1/4000, why can't it do 1/33?  Similarly, why are the aperture choices limited?  Why is it a technical challenge to add extra shutter speeds or aperture settings? Python program to calculate harmonic series Does anyone know how to write a program in Python that will calculate the addition of the harmonic series. i.e. 1 + 1/2 +1/3 +1/4... My character has a bite attack from his race.  What happens if he gains another bite attack from class abilities or spells?  Does the damage increase?  Can he make more than one attack?  Or is it simply that only the better version applies?  I would prefer answers from a Pathfinder context but 3.5e is also acceptable. How to test for minimum amount of items in inventory and execute a command if true I am using the AmazingKit plugin on my Minecraft server to make inventory kits for players. In a command block I have the following command:  /tellraw @p ["",{"text":"Iron","clickEvent":{"action":"run_command","value":"_____"}},{"text":" / "},{"text":"Gold","clickEvent":{"action":"run_command","value":"_____"}}]   Which prints the following result: Iron / Gold.  When a player clicks on Iron, what command should I write where the empty space is _____ in order to check if the player has at least (>=) 20 iron ingots in his inventory and if he/she does, remove 20 iron ingots and execute /kit Basic. If the player has less than 20 iron ingots in inventory, the command won't be executed. Instead, Insufficient amount of iron ingots will be printed out.   Same applies when a player clicks on "Gold".  I'm on 1.14 version What's the smallest positive integer which is divisible by all integers $1, 2, \dots, n$?  Is there a simple way to represent the answer?  Call it $f(n)$ here.   Clearly factorial ($n!$) satisfies the condition of divisibility.  But once you get to $f(4)$ (which is $12$), factorial ($24$) is too large, because it includes as factors both $4$ and $2$, which are redundant.  Multiplying all the prime numbers up to $n$ gives you another estimate, which is this time too low, because you need to include primes multiple times when they're repeated in the factorization of the inputs.  So the answer is somewhere between factorial, and the product of primes.  Is there a simple answer? Any way to open windows from the windows bar using a shortcut? for example to open the first window on the left Ctrl+1, to open the second window on the left Ctrl+2.  Im using xfce4 at this moment, but if under xfce4 is not possible, is there any other desktop environment that permits this?  Since I have several windows open for the same application, I not searching for sortcuts related to the application but as I say below, to the window. How are parentheses interpreted at the command line? Evaluating $\int P(\sin x, \cos x) \text{d}x$ chpasswd apply changes in the chroot directory How can I record demos of my gameplay? I remember seeing a lot of cool Counter Strike videos back in the day. How do you go about recording your gameplay (any game) into an easy to edit format? Do you need special software? How much does it cost?