1.4.1 Getting started

Let’s go through the interface of Quirky step by step. At the top, you find a menu bar with some useful commands:

The ‘Reset’ button allows you to reset Quirky and start from scratch. The ‘Undo’ and ‘Redo’ buttons are self-explanatory. It is useful to know that you can even undo resetting the simulator. Press ‘Share’ to get some options for sharing your program with your friends. We will talk about the ‘Make $R(r)$’ button later.

Below the menu follows the toolbox that contains the basic operations that we learned so far:

For example, the first box, $\bigoplus$, is the NOT operation from Section 1.2, which sends the $[0]$ state to $[1]$ and vice versa. We will discuss the other two operations momentarily. Luckily you do not have to remember all this – simply hover your mouse over each box to see its description.

Below the toolbox comes the heart of the Quirky, the probabilistic bit:

The double line or ‘wire’ corresponds to a bit, initialized in the state $[0]$. You can place operations simply by dragging and dropping them from the toolbox onto the wire. Try now to build the following simple computation in Quirky:⁶⁶ 6 If you read a digital version of these notes then you can simply click on any of the images to open Quirky in your browser. Everything you see in the image will then automatically be included! If this doesn’t work just go to https://www.quantum-quest.org/quirky yourself.

How can we visualize the result of such a computation? Since we will in general be dealing with probabilities, what we are after is in fact a way of displaying probabilities. This is achieved by the green box labeled Prob in the ‘Display’ section of the toolbox. Let’s add it to our computation and see what happens:

It looks like that measurement outcome will be ‘one’ 100% of the time (hover the box with your mouse to confirm our suspicion). Of course, this is precisely what we expect. The initial $[0]$ gets transformed to a $[1]$ state by the NOT operation, so that the outcome will always be ‘one’ according to the measurement rules in Eq. 1.32.