No, they are not!
Then how do they differ?
While a classical computer encodes information in classical bits(0 or 1), quantum computers use quantum bits or qubits than can exist either as zero, one, or both at the same time. They exploit the two main principles of quantum physics – superposition and entanglement. Superposition means that each qubit can represent either a zero or one or both at the same time and entanglement happens when two qubits in a superposition are correlated with one another, the state of one depends on the state of the other. Quantum computers “manipulate the properties of quantum entangled qubits to simultaneously try a vast number of solutions, rather than trying each in turn” [Rob Gear]. They change how we run algorithms today.
If we consider two bits they can exist in as 00, 01, 10 or 11 i.e., just two bits of information, but to describe the one-ness and zero-ness of two entangled qubits in superposition state we need four coefficients or they exist in four states. Thus the amount of classical information contained in N entangled qubits is equivalent to 2^N classical bits. And the most interesting part of this exponential increase is that if we have three hundred entangled qubits, then we have 2^300 classical bits, which is as many particles as there are in the universe! The power of quantum computers to represent N bit in 2^N system states and perform parallel operations on all those states at once allows quantum computers to solve certain complex problems of the world much more efficiently.
Some of the potential applications of quantum computing can be seen in the stimulation of real-world phenomena like in pharmaceutical discoveries, weather forecasts, building optimal solutions, security and encryption, and many more. Several organizations have already invested in quantum capabilities. Let’s look into some of its applications.
Having said all these the quantum computers have some downsides as well, the advantages and disadvantages of supercomputers are inseparable. The qubits are so delicate that any interaction with the environment can cause errors in computation.
A quantum computer is never a replacement for classical computers. They can deliver solutions where sufficient data does not exist or if data is too enormous for classical computers to compute. Its ability to solve complex problems will transform the way we live today.