• Last Updated : 27 Dec, 2019

Google claims to have achieved Quantum supremacy. Well, what is Quantum Supremacy you might ask? It is, using a quantum computer to achieve a task, a well-defined set of problems, that even the fastest than the classical computer. In simple words, when a Quantum computer solves a problem which a Supercomputer can’t, then it is termed as Quantum supremacy. To understand Quantum computing, we first need to know the basics of Quantum Mechanics.

Quantum Mechanics is a branch of physics that explores the physical world at the most basic and atomic levels. At the atomic level, it’s a ghost town, things don’t make sense, things don’t follow classical physics laws, or at least not all of them. Things become probabilistic, nothing is certain and we start talking in terms of waves rather than particles and thus phenomenon like superposition, interference, and Entanglement comes into play.

Superposition: In the presence of a magnetic field, the electron may exist in two possible spin states, usually referred to as spin up and spin down. Each electron will have a finite chance of being in either state until it is measured. It can be observed to be in a specific spin state at the time of measurement. In common experience a coin facing up has a definite value: it is head or a tail. Even if you don’t look at the coin you trust that it must be head or tail.

Interference: The ability of two waves passing through each other to mingle, reinforcing each other where crests coincide and canceling each other out where crests and troughs coincide, similar to the way ripples in water interfere with each other. This results, for example, in an interference pattern of light and dark stripes on a screen illuminated by light from two sources.

Entanglement: When two particles are entangled or intertwined they behave collectively. i.e. at the time of measurement, if one entangled particle in a pair is decided to be in the spin state of ‘down’ (that is, the lowest energy state. When the electron is in alignment with its magnetic field), then this decision is communicated to the other correlated particle that now assumes the opposite spin state of ‘up’. Quantum entanglement allows qubits, including those far away, to interact instantaneously with each other.

Quantum Computing leverages all the above-mentioned phenomenon to function. A bit is the smallest, most fundamental unit of storage that could store a binary value of either 0 or 1. Analogous to a bit in a classical computer, we have a qubit(quantum bit) in the quantum computer which forms the most fundamental unit of storage in quantum computers. The difference is that it can superimpose the two values and can represent 1 and 0 at the same time, each with a certain probability. It is possible at the sub-atomic level. Although a particle can exist in multiple quantum states, once we measure that particle for its energy or position, its superposition is lost and it then exists in only one state. These qubits can be physically represented by quantum particles that can occupy two states simultaneously. This will also leverage the concept of quantum entanglement to process data much faster than anything in this known universe. With all this combined we can make these computers work exponentially faster than even a supercomputer.
We encode parts of the problem that we are trying to solve into complex quantum state and then we manipulate that state to drive it towards what eventually represent the solution. We encode it using a quantum computer, for that we need a chip with qubit which is the carrier of quantum information and the way we control the state of that qubit is using microwave pulses. We send them down the cables and we’ve calibrated these microwave pulses so that we know exactly this kind of pulse with this frequency in this duration will put the qubit into superposition or will flip the state of the qubit from 1 to 0 or if we apply microwave pulses between two qubits we can entangle them. We can measure it through the microwave signal. The key is to develop these algorithms where the result is deterministic. There are two main classes of quantum algorithms.

1. Algo that are developed for decades such as Shor’s algorithm for factoring, Grover algorithms for unstructured search and these algorithms were designed assuming that you had a perfect fault-tolerant quantum computer which is many decades away.
2. Near-term quantum computer application algorithm. Currently, we are in a phase where we need such algorithms and this comes under the topic of research and development.

Google claims that it has achieved the Quantum Supremacy. They announced that their latest quantum processor chip Sycamore had executed a random number generation problem in 200 seconds which would take the world’s fastest supercomputer, which is Summit from IBM, approximately 10, 000 years.
IBM, google’s rival completely discarded the claim by saying that using some very simple techniques summit can easily do the same task in two and a half days.

Google fires back stating “We’re looking forward to when people run the idea on Summit and check it and check our data because that’s part of the scientific process – not just proposing it but running it and checking it.” “At the same time, we’ll be making our quantum computers better” he added.
But we should not ignore the fact that a quantum computer will become exponentially faster as compared to the linear growth of a supercomputer and 2.5 days is still a very long time for some tasks thus it is going to be hard for supercomputers to keep up.
Regardless, this claim gives us a rough idea of what is the future of computers going to look like and who is currently winning the race. For more details, you can read the article – Who Will Win The Quantum Supremacy Debate: Google or IBM?

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