“The history of the universe is, in effect, a huge and ongoing quantum computation. The universe is a quantum computer.” — Seth Lloyd
At subatomic levels, everything we know about classical physics breaks, not just about a small margin but on a massive scale. Welcome to the world of quantum mechanics and quantum computing and be ready to be amazed.
There has been a lot of technological advancement and innovation in human history, but still, there are some computational problems that digital progress can’t seem to solve. These problems need quick solutions, as they can be holding back critical scientific knowledge and breakthroughs, or even the global economy. One might argue that conventional computers have doubled in power and processing speed nearly every year in the last two decades, but they still are not getting any closer in solving these existing problems. Reason? The conventional computer is based on a classical and limited model of computing. But to solve these massive problems, we need to harness a new monster known as a “Quantum Computer.”
The quantum computer is not a faster version of the original computer. It is based on using the quantum properties of particles/waves, and quantum physics to solve the computational problems.
Here we will take a look at where the key difference lies and what makes them so unique.
Limits of present generation of computers
Even though computers are getting advanced every day, there are some hard limits to these developments. Moore’s law states: “The number of transistors in a dense integrated circuit doubles about every two years.”, indicating that the growth rate of classical computers is pretty good. But, honestly, this growth rate is very less. Now, let’s see why I say so.
First there are certain simulations that are very difficult to create and render using a classical computer. Many important problems in physics, especially low-temperature physics and many-body physics, remain poorly understood because the underlying quantum mechanics is vastly complex. The development of quantum computers allows people to study quantum systems, which are impossible to model with a supercomputer.
Also, there are specific problems in the computational world whose complexity increases exponentially, and one such issue is ‘Prime Factorization’. When someone asks you the unique prime factors of a number, let’s say 57 , then you may require just a couple of minutes to say it is the product of 19 and 3(if you have enough practice). But what if the number given to you is a six-digit number? It becomes harder and harder for classical computers to compute the number’s factors, taking more time to compute the solution. Prime factorization is very important as it is used in RSA encryption that protects the data from being misused. The possibility of development of quantum encryption strengthens the confidentiality of the data.
The present classical computers require a huge amount of time to compute these problems. So such a growth rate as predicted by Moore’s law is of less use, as it would require lots of years for the computers to be able to solve such problems.
These problems call for the need of a quantum computer.
QUANTUM COMPUTERS
At first glance, a quantum computer resembles a giant chandelier made of copper tubes and wires — that’s also what the experts have named the structure, a chandelier. In its core are the quantum bits which are used to carry out the calculations. Basically, the quantum computers are based on the quantum properties- mainly “superposition” and “entanglement”- allowing them to miraculously solve these seemingly unattainable endeavors. The qubits (quantum bits) are situated at the bottom and the upper structure is just to try and isolate the qubits from the environment. Now, let me explain it to you what these terms are…
SUPERPOSITION:
You might have come across this term while studying physics, but let me explain it once again, telling its importance in quantum computing. Imagine that you have a coin, so what can be the outcome of tossing a coin? Obviously, it can either be heads or tails. This is similar to how the classical computers work, they store everything in either 0s or 1s, and the amount of information that can be stored in a bit is two as it can only have two different states. But what if I say that both heads-tails or 0 and 1 can occur together in a single toss/observation? Crazy isn’t it?
The quantum properties allow the possibility of superposition of both 0 and 1, even though it may seem counterintuitive at first. Also, you actually don’t know what happens inside a quantum computer !!
The physicists say that it is meaningless to talk about the state of a particle, such as spin, before it’s measurement. It is because the measurement of a quantum particle leads to the collapse of the existing state, known as wave-function collapse and hence giving no information about its previous state. This can also be better understood by the thought experiment, The Schrodinger’s Cat, where the cat can be alive and dead at the same time before someone actually makes an observation. The probabilistic model and superposition of states give rise to the foundation of quantum computers. The other phenomenon mainly used in quantum computing is ‘quantum entanglement.’
QUANTUM ENTANGLEMENT:
This is the same phenomenon which was called “spooky action at a distance” by the great scientist Albert Einstein and is of great use in making a quantum computer. Quantum entanglement is a physical phenomenon that occurs when a pair or group of particles is generated, interact, or share spatial proximity in a way such that the quantum state of each particle of the pair or group cannot be described independently of the state of the others, including when the particles are separated by a large distance. Speaking in easy terms, this means that change in one particle’s state can result in an opposite state change in the other particle (if they are entangled), even when they are at unimaginable distances away from each other. These two properties are very much used in making a quantum computer.
“If you think you understand quantum mechanics, you don’t understand quantum mechanics.” — Richard Feynman
The ‘Qubit’
A ‘bit’ can store 2 states of information in it and hence gets its name. Similarly, the basic unit of quantum computing is called a “Qubit.” When compared to Qubit, the traditional ‘bit’ is pretty dull. Both the Qubit and bit can produce one of the two states as a result of a computation, i.e., 0 or 1. Whereas, the Qubit can also result in the superposition of 0 and 1(in general terms, it can store parts of both 0 and 1 simultaneously).Mathematically it can be represented as follows:
The transistors and electrical pulses form the basis of computation in classical computers and give way to various logical gates and classical computations in digital machines. Similarly, the electron’s spin and other quantum particle properties, like superposition and entanglement, are the basis for the creation of quantum gates and carrying out quantum computing. But the process of creating two entangled particles is not at all easy. It requires entanglement of two individual electrons (while conserving their spin), which is an arduous task. Along with that, it has to be kept in an environment near zero kelvin temperature which is difficult to maintain. The temperature is decreased at every level of the ‘chandelier’ in a quantum computer, and it is necessary because the heat waves and their interaction with the environment causes the qubits to become unstable. Therefore, the quantum computer must be really cold in order to function properly.
Present Scenario
The early development in quantum computing has given rise to quantum algorithms like Shor’s Algorithm, Grover’s search Algorithm, and Quantum Encryption. Recently, Google released “Sycamore”, its 54-Qubit quantum computer processor, and also aimed to prove ‘quantum supremacy.’ Google says that the development of quantum computing has gained much attention in the last three decades.
The physicists and computer scientists are working hard to increase the ‘quantum volume,’ a measure of quantum computer performance by reducing the error rates and trying to enhance its capabilities. The present quantum computers may appear large in size, and almost seemingly useless compared to the classical computers of this generation with respect to size. But, this cannot be a reason to eliminate the need for the development of quantum computers.
There is still a lot of research yet to be done in this field, and companies like IBM and Google, aim at building a better quantum computer. The quantum computer will help us construct digital images of various proteins and physical phenomena, which are in fact very difficult to create using a classical computer. Its applications are also in the field like Cryptography, Finance, Drug Design, Machine Learning etc. These quantum approaches are being explored rapidly, along with the quantum computing community getting bigger day-by-day, leading to better research and developments in this upcoming field. So, lets be prepared for having a promising future full of quantum computing and its wonders.