People tend to stay away when they hear the word “Quantum Computing”. The word itself gives the feeling that it targets scientists or physics researchers, but not your average person scrolling down in their newsfeed. However, quantum computing increasingly becomes more mature to kill its reputation as a hard field. Understanding quantum computing requires as much imagination as math or physics knowledge. In this post, I’m going to briefly spark your imagination about the next generation of computers and give you a glimpse of how IBM makes the experience accessible through your web browser; not access-restricted physics labs.
What is Quantum Computing?
Perhaps you are reading this blog post from your desktop, laptop, tablet or smartphone. All of these devices run on a traditional computer (or what we call: classical computer). Every piece of tech gadget you are using nowadays uses the concepts of classical computing. But what are classical computers and how are they different from quantum computers?
Classical computers use two defined voltage levels (high and low) to represent information. High voltage represents a 1 and low voltage represents a 0. We call these 1’s and 0’s bits (binary digits). It is the flow of high/low voltages in your computer processor (which is a classical computer) that builds up the sequence of mathematical operations which define a computation. In a high-level abstraction, classical computers perform additions/subtractions/multiplication/division on bits (0’s and 1’s). Remember that 0’s and 1’s are represented as low-voltage electricity pulse and high-voltage electricity pulse respectively.
In the quantum world, computers don’t represent data (0’s or 1’s) as electricity pulses. Quantum computers use another type of physical representation for the data such as a single photon, a nucleus or electron. But why do we use other physical objects to represent bits? The answer is that these physical objects can represent not only a 0 or a 1 but also a state where the object is 0 and 1 at the same time; this is what we call the superposition. It is apparent that this superposition cannot be represented using electrical pulses. Wait! How can a physical object be in two completely different states at the same time?
In fact, the object (e.g. electron) is not in both sates at the same time. When we measure the energy of the electron, it can be either in the lowest energy state, which can be used to represent a 0, or in the highest energy state, which can be used to represent a 1. So far, it is the same as the classical bit; whenever we measure the electron energy, it can be either a 0 or a 1. But, before we measure the electron energy, the electron can be in a quantum superposition. The quantum superposition tells us the probability that the electron can be in the 0 or in the 1 states. These probabilities are referred to as the coefficients. The superposition is represented mathematically as:It is also called Qubit (Quantum Bit), where alpha is the probability that the electron is in the 0 state and beta is the probability that the electron is in 1 state. To understand how we can benefit from the superposition state, watch the below youtube video.
Still not convinced by what quantum computers can bring to us? Read this Quora topic!
IBM Quantum Computing Experience
To make use of a quantum computer, you should completely change your mindset and not think classically. It takes a little bit of effort to put yourself in the quantum frame of thinking. However, IBM has made it a little bit easier by offering a cloud-based quantum experience where you can run quantum simulations for free. Running simulations will accumulate points to your account which you can use to deploy and run these quantum experiments on a real quantum computer in their lab.
The above is the quantum composer that you can access through the web browser. On the left, there is Q0, Q1, .. Q4; which are all the qubits (the physical objects like the electron) that you want to measure their energy. They all start with the lowest energy represented by |0>. In the bottom, there are a set of gates that you can use to manipulate the state of the qubits, similar to the AND/OR gates of the classical computers. The pink boxes are used to measure the energy in a qubit. On the right, you can either simulate the experiment which will give you the perfect expected results, or run it on the real quantum computer which will give you a real-scenario computation from the quantum computer. Your goal should be to stack up gates (some take two qubits as input) to solve a computational problem. You measure the energy in each qubit after the operations you built. The user guide of IBM Quantum Experience will give you a plenty of examples to try out.
So What’s Next?
When asked “Why everyone will need a personal computer?”, Steve Jobs replied “Why not? You got a baby and you are asking what you are going to do with him!”. Although quantum computing is in its infancy, they proved to be much faster than classical computers in solving some classes of problems. See this Quora question for inspiration. Quantum algorithms are going to provide us with superior power to solve hard mathematical problems (like traveling salesman problem) in much less time.
Warm up for the next generation of algorithms; quantum algorithms …