The Online Quantum Computer That You Can Use!

This one is cool. IBM has made some of their quantum computers available to the general public via the IBM Quantum Experience website.

I came across this resource only in the last few days. I had no idea that such an amazing resource was made available on the web to the general public. This post describes the website and presents a few simple quantum programs.

Sign up is easy and it only takes a few minutes. Once logged in you can start playing with one of their 5 qubit quantum computers.

The website provides user guides for the newbie as well as the advanced user.

The main part of the interface is the Composer Page in which you get to program in 'gates' that actually manipulate the quantum bits (qubits) and then read them to give you the macro-world outputs of classical 0's and 1's.

To prevent spamming of this limited computer resource, users are given computing credits. Each run of a program uses up credits. When they go to zero you are done but don't worry because IBM will top up your account on a daily basis (I believe).

Also, if you want to test out your programs without using up your credits you can simply push the Simulate button instead of the Run button. You get an unlimited number of simulations and so can test and explore your quantum programs to your heart's content.

For this post I am only going to be using the Simulate button to test the programs and generate the results. I don't want to waste my precious few credits until I feel that am ready to test a proper quantum program.

Test 1 - Let's Just Measure The Qubits

The computer gives you 5 qubits which are all initialized into the |0> state. Here is my first test to see if that is true. I am just going to set up five measurement gates to read the outputs:

The Program:

The Results:

The little pink icon of a gauge in the program composer diagram means that the qubit is being measured. These gates are always needed in any program to read the outputs of your quantum calculation.

When the test is run the results come out with every bit set to |0> which is as expected. Boring yes, but we need to go step by step.

Test 2 - Flipping The Qubits

Let's see if we can simply flip these qubits from |0> to |1> using the 'not' operator which is given by the green 'X' symbol.

The Program:

The Results:

When the test is run the results come out with 100% of the bits flipped from |0> set to |1> which again is as expected.

So far so good. Now on to superposition.

Test 3 - Putting The Qubits Into Superposition

The first two programs used qubits but did not use any superposition which is one of the hallmarks of quantum mechanics. Let's set this up.

Superposition is created using the Hadamard gate. It rotates the vector of the qubit from the initial |0> state to something that is a superposition of both the |0> and the |1> states at the same time.

The quantum computer, if it is good, should make it equally likely to get a |0> or a |1> when the measurement is finally made.

The Program:
For this one I am only going to do 4 qubits so that the results of the output can be seen on one screen.

The Results:

Since I am using four qubits in this test, there will be 2⁴ = 16 states as the possible measured outcomes. Each of the sixteen outcomes is equally likely. Since 1/16 = 0.0625 the results should all be more or less close to this value. The outcome chart shows that this is basically true.

The simulations only perform 100 test shots so there will always be statistical variation around the expected results.

Test 4 - Qubit Entanglement

The next hallmark of quantum mechanics and quantum computers is that you can entangle the qubits. Entanglement is critical for quantum computing because if it is done properly you can model systems that would be very hard, if not impossible, to model using classical computers (i.e. breaking codes, traveling salesman problems etc.).

For this test I am just going to program in one of the Bell Theorem examples given in the advanced section of the IBM Q-Experience website.

The Program:

The Results:

Bell's Theorem is very deep and it would take at least an entire post (probably several posts) to explain it properly. In brief, Bell's Theorem proves that entangled quantum states will yield outcomes with probabilities that cannot ever be replicated using the interaction of classical mechanics.

Per the IBM web page:

"Bell showed that if these measurements are chosen correctly for a given entangled state, the statistics can not be explained by any local hidden variable theory, and that there must be correlations that are beyond classical."

Closing Words

As I said at the start of this post, I came across this resource only in the last few days. I think this is an amazing find and if you are oriented towards the STEM fields then I encourage you to sign up and start playing around with it as it is an incredible opportunity for education and if you have the skills, maybe even research.

All images that do not have explicit credits are screenshots that were taken during my live setups and executions of the quantum programs. This is a fair use activity and falls within Steemit publishing guidelines.

_{I, Procrastilearner, donate the above image to the Public Domain.}