Quantum computing has intrigued and fascinated us since decades and still remains elusive.While technology has advanced by leaps and bounds, quantum computing is still in its infancy. However, with the rate we are advancing scientifically, quantum computers necessarily gonna be commercially viable and will certainly replace classical computers of today, though it will take time.
Quantum computers make use of the principles of quantum mechanics (superposition and quantum entanglement - more on this later) to achieve the speed and efficiency which they are well known for. While classical computers use transistors as their building blocks, quantum computers are based on qubits which is a fundamental digital storage unit in quantum computers.
In classical computers a bit represents any of the 2 possible discrete voltage levels (HIGH = 1 or LOW = 0) flowing through a digital circuit which is called a flip flop which is a binary storage device made of transistors. It's the flip flop which stores binary data in classical computers. Below diagram represents these voltage levels.
In quantum computers, qubit represents the atomic unit of data which stores info and exists in superposition which can be 0 or 1 or both at the same time. A qubit can be electron, photon, ion or an atom and their respective control devices which work in tandem act as registers called qubit registers and quantum processors. Since the qubits can be in both states simultaneously, a quantum computer is light years ahead in terms of speed when compared to their traditional classical counterparts. It has faster processing capability than the fastest supercomputer we have today.
In a quantum computer, electron spin is used to represent the state of a qubit and the control devices like quantum dots, ion traps, optical traps etc. use electric fields to change the electron spin and hence control qubit states. These control devices are made of semiconducting materials. New advanced techniques of creating qubits using super conducting materials are being discussed and researched by Scientists and Engineers.
While quantum computing is advancing , we still have not been able to build a full fledged general purpose quantum computer.The quantum computers today are more geared towards solving complex computing problems only like an ASIC chip does and they are 100 times slower on some other computing operations like gaming video streaming etc.
They are expensive and produce a lot of noise in the qubits which makes them more error prone by destroying the data stored in qubits.
They are not energy efficient and thus consume a lot of power and also are every expensive.
They are to be maintained under sub zero temperatures which again calls for huge maintenance costs.
IBM Q Experience
IBM has exposed a quantum computer on cloud here. It's a good platform for quantum computing enthusiasts to create and run programs that execute on quantum computer like the Shor's Algorithm which runs in Polynomial time on quantum computer but takes exponential time on classical computers.
