I was trying to show some slides in my dropbox folder to my collaborator with my android tablet. I only have the pptx file and it displays so slowly on my ASUS transformer. It came to me maybe I can connect to my desktop in office remotely to convert the slides to pdf. I did…

# Month: September 2012

## Over-justification Effect

I am watching an online course on gamification. It mentioned explicit motivation and implicit motivation and described interesting examples of over-justification effect that subjects can be demotivated by rewards. The first one is about drawing by kids. Many kids are very interested in drawing and are inherently motivated to draw. However, when they are given…

## Random Thought on Steins Gate

I am more than half way through Steins Gate. Apparently, it will become one of my all time favorite. Okay, there will be spoilers here. For those who didn’t watch it, go watch it now! It doesn’t matter if you are an anime fan or not. This one will definitely change your attitude towards anime…

## TF-IDF

Here are some notes of TF-IDF as a measure for identifying keywords in a document. To efficiently indexing documents for future search, it is important to identify the keywords in a document. For a word to be a good keyword, first, it should be relatively rare. This can be measured by the inverse document frequency (IDF), which…

## Locality Sensitivity Hashing (LSH)

I am studying an online class on Web Intelligence and Big Data. Dr. Shroff described a very nice example of LSH. Below are some quick notes. The idea of LSH is essentially the same as dimension reduction. We have some data vector that can be in very high dimension. By processing hash data instead, we…

## Bernstein-Vazirani Algorithm

Here is some personal notes on Bernstein-Vazirani algorithm. Assume that we have a black box that does nothing but compute , where is an input binary vector and is another binary vector that we don’t know its value. Note that all operation is bit-wise and so the output is binary also. The question is how…

## Hadamard gates on multiple qubits

The effect of applying Hadamard gates to multiple qubits is rather subtle and is used in many quantum algorithms. Consider input qubits, . What will be the output if we apply the Hadamard gate to each of the qubit? Note that a Hadamard gate maps to and to . So ignoring the scaling factor, the…

## Fixing ogv problem on YouTube

It appears that YouTube occasionally hiccups on some ogv files and produces green screen. The following may not be the best solution. But it almost always solves the problem by first transcoding the video to avi. In linux, it can be done by mencoder as follows mencoder input.ogg -ovc xvid -oac mp3lame -xvidencopts pass=1 -o…

## Quantum Teleportation

Let say Alice wants to pass her qubit to Bob. By no cloning theorem, we know that Alice cannot duplicate her qubit to Bob. However, she can “teleport” her qubit to Bob if they share a Bell state . First, Alice will apply CNOT gate from to her qubit in the shared Bell state. This…

## Proof of no cloning theorem

I’m still studying the online course on quantum computing where Prof. Vazirani went through the no cloning theorem. It is very interesting to see that something that can lead to some very subtle consequence can also have a very simple proof. Below is a summary. Basically, the theorem states that no quantum state can be…