Quantum Computing : Changing The Focus From How Humans Compute To How The Universe Computes
Authored By -Dr. Raju Narayana Swamy IAS
Quantum Computing is a new paradigm of computation based more directly on quantum physics. Unlike digital computers which are based on the established principles of classical logic, quantum computers manipulate qubits with exquisite control allowing for the interference of information like waves on a pond to amplify the answers we seek in a sea of possibilities. The structure of quantum computation is based on a very simple concept- the replacement of the elementary unit of information, the bit, with the qubit, a much more complex object which in principle can contain an enormous amount of information. Qubits are made using physical systems such as the spin of an electron or the orientation of a photon (light particle).
Superposition And Entanglement
The basic principles of quantum computing are superposition and entanglement. Superposition is the ability of a quantum system to be in multiple states simultaneously. A classic example is the flip of a coin which normally yields either heads or tails. But if you spin it, it has got a chance of landing on heads or on tails and until you measure it by stopping the coin, it can be either. Superposition is like a spinning coin and it is one of the things that makes quantum computers so powerful. Entanglement occurs when multiple qubits are correlated with each other and means that the two members of a pair of qubits exist in a single quantum state. Changing the state of one of the qubits will instantaneously change the state of the other one in a predictable way. Einstein called this behaviour a ”spooky action at a distance”.
The main advantage that quantum computers have over classical ones is parallelism. But while parallelism sounds amazing in theory, it is not immediately useful on its own. This is because a quantum computation can calculate a superposition of the 2n numbers , however a measurement still needs to be performed in order to extract information from the quantum computer. An analogy is of a secret invisible scratchpad on which all the 2n numbers are located, but where nature shows you only one random page at a time and then burns the scratchpad. Needless to say, you would need to run the quantum computer at least 2n times to get all the numbers therefore negating any advantage over classical computers. If you are unlucky, due to the randomness of quantum physics, you could repeat the computation a number of times and still not see all of the possibilities.
Difference between classical computers and quantum computers
Classical computer Quantum computer
Output Deterministic Probabilistic
Gates used for processing Logic Gates Quantum logic Gates
Operations Use Boolean Algebra Use Linear Algebra
Circuit Implementation Implemented in macroscopic technologies (Eg: CMOS) that are fast and scalable Implemented in microscopic technologies (Eg: Nuclear Magnetic Resonance) that are slow and delicate
Will Quantum Computers Replace Classical Ones?
The answer is no, due to the simple fact that quantum computers are only practical for certain types of problems. In fact, classical computers are better at some chores. Examples include email and excel. Quantum computers are not just about doing things faster or more efficiently. They will let us do things that we could not even have dreamt of without them- things that even the best supercomputer just is not capable of. In this context, mention need to be made of the concept of quantum supremacy that refers to the moment in which a quantum computer performs a task in much less time than it would take on a classical computer. In 2019, Google claimed to have performed such a task on a 53 qubit quantum computer named SYCAMORE which took only 200 seconds. They claimed that it would take a classical computer 10000 years to do the same task, but shortly afterwards IBM suggested that an improved classical supercomputing technique could theoretically perform the task in just 2.5 days . In July 2021, a team in China demonstrated that it has the world’s most powerful quantum computer, leapfrogging the previous record holder Google.
Applications Of Quantum Computing
a) Artificial Intelligence (AI)
AI counts on processing large and complex data sets. It is responsible for learning, inferring and understanding. Quantum computing can make it easy and more accurate as it can train models over huge data sets. Natural language processing is another example. Quantum computers can pave the way for understanding phrases and speech in real –time with improved quality which is computationally costly with today’s computers. But the best application of quantum computing in AI will be found in the field of machine learning.
b) Chemistry, Biology, Healthcare and Nanotechnology
Breakthroughs are expected in these fields as quantum stimulation can help scientists better understand molecule and sub molecule level interactions. One of these is to understand how an enzyme, nitrogenise, used to make fertilizers actually works. Superconductivity and magnetism are quantum mechanical phenomena and quantum computers may help us understand them better. IBM recently simulated the molecule Beryllium Hydride – a small molecule with just 3 atoms – on a 7 bit quantum processor. It also needs to be mentioned that there is a group at the University of Chicago that is looking into photosynthesis. It is a quantum mechanical process. The long term goal is to understand this process and then use it in photovoltaic cells.
c) Other applications
NASA could use quantum computing to establish models of the space climate, to simulate planetary atmospheres or to analyze enormous quantities of data. Google can put in the technology to improve research in the internet and in voice recognition. It can help in solving some of the fundamental questions in physics related to gravity, black hole etc and could give a boost to the genome project. The collection of data regarding climate change can be streamlined in a better way through quantum technology. Tsunamis, droughts, floods and earthquakes may become more predictable with quantum applications. A few other segments where revolutionary changes can take place include cloud systems, automotive sector (optimizing large autonomous fleets), energy (grid optimisation among others), finance (risk analysis, portfolio optimisation and process of credit cards), logistics (supply chain and inventory optimization) and pharma (personalized medicine and genomics to name a few).
Threat To Cyber Security : Quantum Computing Vs Cryptography
The dark side of quantum computing is the disruptive effect that it can have on cryptographic encryption, which secures communications and computers. Quantum computing could make today’s cyber security obsolete.
The most commonly used modern internet encryption protocol is RSA which relies on encrypting messages with keys that are made out of very large integers. To break the encryption protocol, an eavesdropper would need for factorize this very large integer into its prime factors – a problem that classical computers cannot solve in a reasonable amount of time. However in 1995, Peter Shor proposed a quantum computing algorithm based on superposition and interference that drastically speeds up the factoring process. Shor’s Algorithm can theoretically break modern encryption schemes although quantum hardware is not sufficiently advanced yet to make this decryption practical. If it were, all our bank details and military secrets could be easily hacked.
The only way to fight back is with quantum encryption which relies on the uncertainty principle – the idea that you cannot measure something without influencing the result. Quantum encryption keys are completely unbreakable (ie) they cannot be copied or hacked. Just like the fear of a possible Y2K bug led to massive investment in computer system upgrades, fear of a possible quantum computer using Shor’s Algorithm means that developing quantum-safe encryption systems will be prudent in specific sectors.
Feynman predicted that before 2050 we would have a computer that we could not even see. Given how classical computers went from being the size of a room in the 1960s to an iPhone within a few decades, governments and industries are investing billions of dollars towards making quantum computers realistic.
Mention also needs to be made of the technological challenges encountered when improving a quantum computer. The foremost among them is the risk of random photons outside the quantum computer leaking into the computer and causing accidental changes – called noise – to the quantum state. To reduce the number of these environmental photons, the quantum computer needs to be cooled down to near absolute zero (around -450 Degree Fahrenheit), a difficult proposition indeed.
Quantum computing is a beautiful fusion of quantum physics with computer science. However it is now in its infancy. Just as Copernicus showed that the Earth was not the centre of the Universe and Darwin proved that humans evolved from other animals, we are now beginning to see that computations are not centred on humans. With quantum computing, the focus changes from how humans compute to how the universe computes. What we are going to discover is impossible to say, but now is the time for exploration and innovation. The greatest years for quantum computation lie ahead of us.