PyQuil

Quantum programming with PyQuil and Rigetti

October 30, 2018

Rigetti Magic 8 Ball

Introduction to Quantum Computing

This example highlights in a simple way how we can employ and deploy the Quantum Simulation Code from Rigetti to have some fun and create a magic 8 ball. You might seen them, there is a photo below, its a sphere that resembles the black 8 ball in pool. Shaking the ball, randomizes and highlights one of the surfaces (typically 20) with some text on it. The use case is to crack the stalemate when making decisions. Here we will use the quantum equivalent of shaking to perform the randomization. You can pull the code from github at github

How it works

Create a number of qubits, the exact number of qubits will be dependent upon the number of options. Here we show the canonical existence of a 20 sided Magic 8 Ball.

Takes advantage of the Quantum superposition which means that we can cannot know what state a qubit is in until we measure it. We have two possible measurement results for each qubit.

Qubits

A qubit is somewhat akin to the quantum equivalent of a bit, but it can exist in a mixed state, a superposition of two states. We thus put a series of qubits into a superposition that according to the Born rule has equal probability of being in state |0> and state |1>. We can perform this very easily by taking an initial state |0> into a|0> + b|1> with a transformation called the Hadamard or H in the pyquil tool set.

You can create a Program with any number of qubits with the following code, but to create an empty program, you can use

p = Program()

For each qubit, we can append to p with the qubits we wish to add, in the state we want them in (i.e. transformed with a Hadamard)

for i in range(0, nQubits):
        p += Program(H(i))

We can now state how we want to measure our qubits. We want to measure them all. And for that we can use the .measure_all() and then convert our readout into an actual number that is effectively random. Note how we use the positional information and the qubit measured state to generate an effectively random number, up to N.

Running the Code

python magic8ball.py

Example Output

('Number of Qubits: ', 5)
('Number of Quantum possibilities: ', 32)
('Number of possibilities you chose: ', 20)
('Magic 8 ball response: ', 'Signs point to yes.', 9)

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