Quantum computing is one of the most promising research topics of this generation. Quantum theory has left the world bamboozled both in terms of the theoretical possibilities that have already been explored by researchers and in the practical applications that this new technology might lead to. For a computer scientist, the speedup of Quantum computers resides in the ability of such computers to do parallel processing, in a way never imagined before. Quantum computers are fundamentally different from their classical counterparts. At the core of a Quantum computing is the principle of Quantum Superposition, which like all Quantum theory, is very hard to visualize. This blog will be directed at throwing some light into this ‘spooky’ science , as Einstein himself called it.
Principle of Quantum Superposition
To be fair to Einstein, the concept of superposition does seem to be impossible in the sense that it is not possible to observe this phenomenon in the world we physically observe everyday. It is not like gravity, which can be proved by something as simple as a falling apple. The question of superposition only arises in the world of subatomic particles. In that realm of existence, the laws of classical physics seems to stop working entirely. The principle of quantum superposition states simply that a quantum particle can exists in 2 distinct locations at the same time. According to this theory, an quantum particle can exist simultaneously in multiple states, unless the operation of measurement is made.
To drive home what quantum superposition means, closely observe the short video above. The video depicts through animation, what is known as Qubits in Quantum computing. A Qubit is the basic unit of quantum information, a parallel to the Bit as the basic unit of classical information. As shown in the video, a Qubit can be both 0 and 1 at the same time, till the time it is observed. This property of the Qubit to be in a superposition of 2 states at the same time is what provides the Quantum Computers with exponential speedup when compared to Classical Computers.
Let’s take a step back from talking about Qubits and Quantum computers. Quantum superposition is something that happens throughout nature. Scientist believe that natural computations like chemical reactions and molecule formation happens so quickly because of the inherent quantum superposition of the subatomic particles. To drive this point through, let me take the example of the most commonly know element on earth, water. I hope all readers have a fair idea about how the water molecules are formed. Oxygen shares it’s 2 electrons with each of the Hydrogen molecule and forms a bond with them. According to classical chemistry, this sharing means that the shared electrons reside in the vacant space between the Hydrogen and Oxygen molecules. According to Quantum scientists, this is not exactly true. The shared electrons actually exists in superposition between the Oxygen and Hydrogen molecules. This means that the shared electrons are simultaneously present in both Oxygen and Hydrogen molecules and the position of these electrons need not always be in between the 2.
Exponential speedup in Computation power
One of the most studied applications of quantum superposition is the possible speedup in computation. To explain this, we have to revisit the Qubit and it’s properties. All computers in the world, from the biggest supercomputer to a small smartwatch, work on the same principles as the Turing Machine built during the second world war.
This machine works based on the presence or absence of the clicks caused by the rotation of these mechanical levers. Although we have moved on from mechanical levers to digital bits, the same concept still governs all our computing efforts. The concept of Qubit can easily be explained by saying that it can be 0 and 1 at the same time. But in the mechanical case, having a click and having no click at the same time, seems like a absurd case to make. This is the reason why even researchers working on Quantum Technology are not able to fully visualize it’s power and capabilities.
However, let us try to make some sense of the situation here. In any way, computing power directly correlates to the number of computational states which exists at the same time. Let’s take the example of a navigating a maze.
Consider that a quantum particle is going through this maze. Remember that a quantum particle have the unique property of being at 2 places at the same time, due to the principle of quantum superposition. So, when a quantum particle encounters various paths to take within the maze, it can decide to take all of those paths at the same time using superposition. If you think about it, this process closely resembles the paradigm of parallel computing. Due to quantum superposition, the quantum particle is able to navigate the maze in exponentially less time than the classical bit.
A classical bit, on the other hand, does not posses this magical ability of superposition. A classical bit is easier to imagine, as we can just imagine our self going through a maze. At a time, we can explore only one of the paths in the maze at a time. If the path the classical particle takes ends up in a dead end, we have to backtrack all the way back and start again by choosing a different path. As you can see, this is a time consuming process and we would lose horribly if we were to race against the quantum particle. Scientist believe that it is this unique property of quantum particles which results in the fast pace of computations in the subatomic level.
Conclusion — World is getting weirder
We can never imagine what such a new technology can achieve in the next 10 years. Researchers are working on creating full fledged quantum computers to answer problems which are just too hard for classical computers today. Many fields such a cryptography, machine learning, information security may soon undergo a drastic change due to the advent of the Quantum computing capabilities. World of science and technology is getting weirder and harder to explain day by day. We cannot even imagine how the entire concept of computing might change in the coming years, and that’s what excites me the most!