Google released a paper in the scientific journal, Nature. It showed the Sycamore quantum processor and how it could perform, completing a target computation in 200 seconds. This is a big deal according to Google because according to them, the fastest computer in the world currently would take 10,000 years to perform the same calculation. The ability of a quantum computer to perform a task that is practically impossible with a traditional computer is quantum supremacy.
Whatever you do on a computer is ultimately converted to 0s and 1s and is represented in bits where each bit can either be a 0 or 1. In a quantum computer, this fundamental aspect changes. A quantum computer uses quantum bits or qubits which can represent both 0 and 1 simultaneously. A quantum computer is able to do this by applying key concepts from quantum mechanics: superimposition and entanglement. Superimposition is the phenomenon that allows quantum computers to simultaneously be in multiple states (both 0 and 1).
Only when the qubit is finally measured to check for the result of a calculation, it collapses to either 1 or 0. The Sycamore chip developed by Google uses a 53 qubit processor, which is capable of holding 2⁵³ states simultaneously. Theoretically, a 100 qubit quantum computer would be more powerful than all the supercomputers on the planet combined.
Entanglement is the other important feature that differentiates quantum from classical. This phenomenon allows pairs of quantum bits to be interconnected in a way that a change in the state of one will affect the state of the other.
Superimposition and entanglement make quantum computing dramatically and exponentially faster than traditional machines. Whereas in a traditional machine, doubling the number of bits doubles the processing power, in a quantum computer, doubling the number of qubits results in an exponential increase in processing power.
A simple expression of this concept is to look at how both the computers find the right path through a maze. A classical machine tries every path one by one until it comes across the right path that allows it to escape the maze. A quantum computer tries all paths at the same time and provides the right path instantaneously.
The quantum superimposition state is extremely fragile. At any moment, disturbances (or noises) such as slight changes in vibration or temperature can result in the interference and breakdown of quantum behavior. This is known as decoherence. This is why quantum processors are built inside environment controlled, super-cooled rooms. However, it should be noted that these controlled environments do not completely eliminate the possibility of errors.
Google CEO Sundar Pichai, gave an interview after the publication of the paper, stating that “the real excitement about quantum is that the universe fundamentally works in a quantum way, so you will be able to understand nature better.” However, in reality no one really knows what quantum computing has in store for us until it becomes more accessible.