add deutsch-oracle example

[danbev]

Summary

This commit adds an example of the Deutsch-Oracle algorithm to qiskit-sim.

Details and comments

This is an initial version of adding an example of the Deutsch-Oracle algoritm. I'm looking for feedback on the format and the algorithm (to verify that I've not misunderstood anything).

The goal for this is to help people like me that are learning about quantum algorithms to have a JavaScript example to run/step through/look at. I'm also interested in hearing if this is understandable without a companion doc or more code comments.

Example output:

$ node
Welcome to Node.js v12.4.0.
Type ".help" for more information.
> const d = require('./packages/qiskit-sim/example/deutsch-oracle.js');
undefined
> d.balanced0()
        Balanced function   f(0) = 1, f(1) = 0

          column 0      column 1      column 2      column 3
wire 0 -----------------[h]-----------[uf]----------[h]-----------
                                       |
wire 1 ---[x]-----------[h]-----------[*]-------------------------

Oracle matrix (uf):
[ 0, 1, 0, 0 ]
[ 1, 0, 0, 0 ]
[ 0, 0, 1, 0 ]
[ 0, 0, 0, 1 ]

Final state:
0+0i|00>0%
0+0i|01>0%
-0.70710678+0i|10>50%
0.70710678+0i|11>50%

Show tensor state:
0  ⌈-0.7071067811865474⌉
   ⌊0.7071067811865474 ⌋
1  ⌈-0.7071067811865474⌉
   ⌊0.7071067811865474 ⌋

Measure qubit 0:
qubit[0]: |1>, Function is balanced!