QUANTUM COMPUTER: INFINITE MACHINE?
SO WHAT PREVENT US FROM MAKING THE SUPER COMPUTER WITH INFINITE PROCESSING SPEED.
1. LIMIT OF TRANSISTOR SIZE AND END OF THE MOORE'S LAW:
Our computer is modelled on the decade old Transistor Based Microprocessor. Transistor is nothing but switch which control the flow of electron between Source & Drain. According to Moore's Law, no of transistors in a chip will double approx in every 2 years. Current size of the Transistor( distance between Source and Drain) in the chip is just 22 nm ( enough to accommodate just 50 Silicon Atoms). At this rate, we will achieve 5 nm Transistor ( enough to accommodate only 10 silicon atoms) by 2025. Here Comes the problem.
In this 5 nm gap between source and Drain, transistor wont work since Quantum Tunneling Effect ( one property of subatomic particle in which electron will pass through the barrier in it's path) will take place. Since Processing speed of the chip is directly related to the size of the Transistor, we are nearing towards the Upper Limit of the processing speed of a single Chip. Beyond 2025, further reduction in the size of transistor & increasing the processing speed of a single chip will be almost impossible.
2. SPEED OF ELECTRONS
Speed of the electron in Transistor is just 10 % of the speed of light which is limiting the size of the chip and it's processing speed.
3.HEAT GENERATION & POWER CONSUMPTION:
Power Consumption of Tianhe -2 is 27 MW for just 33.8 Peta FLOP operation. At this rate, we would require 8 Lakhs MW Power ( India's total installed power capacity is just 2 Lakhs MW only) to run the 1 Zetta FLOP Super Computer to accurately predict the Golabl Weather Pattern.
This is the main restriction of the Transistor Based Classical Computer since transistor will generate heat at exponential rate for linear increase in it's frequency.
4.DIGITAL BIT:
Classical computer stores information in the form of digital Bit in the Transistor. So Transistor can take only one position at a time ( either 0 or 1) whereas Qubits ( in Quantum Computer) will take 0 or 1 or ( 0 and 1 at same time which is called Quantum Superposition).
SO ONLY WAY TO ACHIEVE THE INFINITE PROCESS SPEED IS TO MOVE OUT FROM THE TRANSISTOR BASED DESIGN. QUANTUM COMPUTERS ARE PROMISING ALTERNATIVE. Let us See How it works?
QUANTUM COMPUTER:
Qunatum Computers are totally different from the Transistor Based Classical Computer. It works on the principle of Quantum Mechanics. HOW IT IS ACHIEVING INFINITE COMPUTATIONAL SPEED?
Quantum Laws are weird and totally different from Classical Laws of Physics. Quantum Computers are based on the following Quantum Properties
1. Quantum Super Position ( Sub Atomic particles can be present at multiple place at same time and it can take multiple position at same time)
2. Quantum Entanglement ( Two entangled subatomic particles transfers information between them instantly ( Faster than speed of light) irrespective of distance between them.)
3. Quantum Tunneling ( According to this property, sub atomic particles can pass through any barriers in it's way and we can't block their path)
THE ABOVE QUANTUM PROPERTIES ARE WELL KNOWN AND TESTED IN LABOR TIES EVEN THOUGH SCIENTIST HAVE NO CLUE ABOUT HOW IT WORKS.
MECHANISM OF QUANTUM COMPUTER:
Quantum Computers stores information in the form of Qubits. We can use any subatomic particles like electron, proton, neutron as Qubits. How it really works?
We know that sub atomic particles are spinning on it's own axis like earth spins.We can control the spin of the subatomic particles by applying magnetic filed since it has charge. So spin down is "0" and Spin Up is "1" and due to Quantum Superposition, it can take both 0 and 1 at same time (Seems Weird. Scientist have no explanation for this. Hypothesis is that subatomic particle can be present at multiple universe at same time which allows them to take 0 & 1 at same time).
So 2 Qubits can have the following 4 position together at same time where as classical computer will take only one of the following position at any time.
Qubit 1 Qubit 2
A 0 & 1
B 1 & 0
C 0 & 0
D 1 & 1
SO PROCESSING SPEED OF THE QUTANTUM COMPUTER IS EXPONENTIAL. IF WE HAVE 500 QUBITS ( OR 500 ELECTRON), WE CAN PROCESS 2 ^ 500 NO OF POSSIBILITIES AT SAME TIME( WHICH IS MORE THAN NO OF ATOMS IN THE OBSERVABLE UNIVERSE).
DESIGN CONSTRAINTS FOR QUANTUM COMPUTERS:
Though, quantum computers has potential for infinite processing speed, design of such computer require cutting edge technologies due to the " Quantum Dechoherence" effect since subatomic particles are very sensitive to the environment. It is mandatory to keep quantum processor at temperature in between - 273 Deg C to Absolute Zero ( minimum temperature attainable in this universe) and in isolated condition from all from of Electromagnetic waves & Magnetic field to maintain it's "Quantum Superposition".
Another problem is that Heisenberg's uncertainty principle which rules out the exact measurement of two states of the sub atomic particles. Solution to this problem is Quantum Entanglement. But technologies to measure the state of Qubits through Quantum Entanglement is still in nascent stage.
Another major constraint in the Quantum Computing is the creating algorithm for Quantum Processing
COMMERCIALLY AVAILABLE QUANTUM COMPUTERS:
Some of the Quantum Computers are commercially available in the market. Example is "D Wave two" 512 bit Quantum computers works on Quantum Adiabatic process designed by US based D Wave System. It is installed in Nasa & Google's Quantum Artificial Intelligence Lab at USA to study about Machine Learning & other related fields.
SO QUANTUM COMPUTERS ARE LOOKING LIKE PROMISING ALTERNATIVE FOR TRADITIONAL TRANSISTOR BASED CLASSICAL COMPUTER.
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