When a subject is both philosophically exciting and mathematicallycomplex, it's easy to develop weird ideas about it, like quantum entanglement,qubits and superposition. So, in this write-up, I have chosen to clear up somecommon confusion about what these buzzwords mean. I am also recalled of "Virus"in "3-Idiots" saying, "this is not a philosophy class, oon dou words ka mattlabsamjao bass."
Superposition is something that we see in the routine affairs of our dayto day life. Imagine playing two notes on a guitar; the sound we hear is asuperposition of these two notes. Quantum superpositions are also made up of acombination of states, with the key difference of performing a measurement.Despite the system existing in a perfectly well-defined superposition state,when we perform certain measurements on these systems we may get randomoutcomes. So, the magic is actually observed as a special kind of quantumrandomness. Now, entanglement is the idea that we can't describe two entangledparticles independent of each other. Their states are tied together in waysthat can't be recreated in our classical world. If we measure one of them, wemight observe that it behaved randomly, but at the same time, it tells us whatto expect when measuring the other particle, in the same way. According toresearchers, this phenomenon of perfect correlation holds true even if wemeasure the entangled particles at opposite ends of the galaxy.
Harnessing entanglement for computation is considered to be a crucialingredient for speeding up computation using quantum computers. Just like withclassical computing, we need a set of instructions that represent aproblem-solving approach (i.e. an algorithm), and a machine that can executethose instructions (i.e. a computer). The fact that quantum computers canactually create superpositions, entanglement, and other quantum effects meansthat we can write algorithms in a new way than before. Qubits are fundamentalto quantum computing and are somewhat analogous to bits or binary digits in aclassical computer. Qubits can be in a "1" or "0" quantum state. But these canalso be in a superposition of the "1" and "0" states. However, when qubits aremeasured, the result is always a "0" or a "1" although the probabilities of thetwo outcomes, depends on the quantum state they were in.
All computing systems rely on a fundamental ability to store andmanipulate information. We are already experiencing tonnes of benefits everydayby using the classical computers. Quantum computing refers to the newbreakthroughs in science by the use of quantum computers, which could spur thedevelopment of more efficient devices and structures, to new machine learningmethods to diagnose illness and improve medication to save lives and evenimprove our financial strategies to live well in retirement. For problems abovea certain size and complexity, classical computers can't work well as thesedon't have enough computational power. To stand a chance at solving such problems, say searching for darkmatter or building more stable silicon chips or solving an intricate businessproblem, we needed a new kind of computing. The idea of quantum computing was proposed by an American physicist PaulBenioff in the early 1980's. He is best known for his research in quantuminformation theory describing the first quantum mechanical model of a computer.This work has continued since then and has now encompassed quantum robots andalso the relationships between foundations in logic, Math's and Physics.Quantum computers have the potential to process exponentially more data ascompared to classical computers. These could also simulate things that aclassical computer could not. These perform the calculations based on theprobability of an object's state before it is measured. A quantum computerharnesses some of the mystical phenomena of quantum mechanics to deliver hugeleaps forward in processing the data. Until a few decades ago, quantumcomputing was a purely theoretical subject, but today the real quantumprocessors are being used by researchers all over the world to test outalgorithms for application in a wide variety of fields. The field of quantumcomputing is a subfield of quantum information science. There are however, anumber of technical challenges in building a large scale quantum computer.Sourcing the parts of quantum computer is very difficult. Quantum computers aredifferent from traditional computers based on transistors. These need Helium-3, a nuclear researchby-product and certain special cables that are made by a company in Japan. Oneof the challenges associated with quantum computing is instability. Becausecalculations are taking place at the quantum level, the slightest interferencefrom the environment can disrupt the process. That makes quantum computers veryexpensive to build and maintain. A useful universal quantum computer – hardwarealone – comes in at least $10bn. Owing to these limitations, quantum computingin full bloom is yet a distant dream. D-Wave, a Canadian company has taken thelead in being the first to sell computers exploiting quantum effects. Similarly Google AI, a division of Googlededicated solely to artificial intelligence, in partnership with the U.SNational Aeronautics and Space Administration (NASA) has claimed to have achievedquantum supremacy as reported in a paper published on 23 oct 2019. While somehave disputed this claim, it is still a significant milestone in the history ofquantum computing. The goal that aprogrammable quantum device can give a better insight in the problems ofscience, engineering or business that classical computers practically cannotdo, irrespective of the relevance of the problem is what we mean by quantumsupremacy. Einstein had said that if quantum mechanics were correct, then theworld would be crazy. This is true in the sense that atoms or elementaryparticles behave as if not real but representing a sea of possibilities andpotentialities rather than a single thing or a fact.
Qudsia Gani is Faculty (Physics), Cluster University Srinagar