How Quantum Computing works- Easy explanation
Welcome to another blog of Daily life Hacks. Here we will discuss about Quantum Computing. Please note that, this explanation is a basic understanding of Quantum Computing as a Layman. This explanation can’t be used for mathematical explanation or derivation. To know about quantum computing, first we need to know what is a computer and how it works.
What is a computer? A computer is a device/machine which can compute/calculate certain mathematical task. The name itself defines it’s work. It can be a calculator, a digital thermometer or a digital volt meter or a computer and many things. Now it is wondering that if a computer is basically a device which can compute/calculate then how it can run a movie or browse internet or play a song. All these operations are done by conversion of arrays of bits into electrical/optical/electromagnetic signals etc. A classical computer does these operation using it memory storage. Basically there are two types of memories in classical computer. ROM and RAM. ROM are the hard disk memory use to store data. RAM is the memory that the processor/CPU uses to do the instantaneous calculations like conversion/reading/writing from the database. Processor is the brain of the computer.
What is inside a memory is the main game play here. Fundamentally a memory ROM or RAM is array of large numbers of transistors. A transistor is a switch which represent two state ON and OFF. ON means 1 and OFF means 0. Everything in digital world is described in stack of 0s and 1s. To know further operations of a computer we will start from very basic operations of addition in a calculator.
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In the circuit diagram above we can see inside of a addition function that is a OR gate circuit there are two transistors. As we know the operation of a transistor, when a voltage is applied to gate then the current passes through source to drain. Here 1 is some voltage and 0 is zero voltage. Now if we will put the values of A and B we will find the abject in the output as shown in the table.
Likewise, there are many logic gates for different mathematical operations. Above calculator is a calculator which can only add 0s and 1s. Now people need to a calculator which can add 1 to 15. Let’s make it. First we need to convert 1 to 15 numbers into binary digits 0s and 1s. Why, because computer only understands transistor ON or OFF.
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So to make a calculator to add 1 to 15 numbers we need four OR gates in parallel. Above example is to understand the need of transistors grows exponentially for more complex and bigger calculation. We need more and more numbers of transistors.
Everything that we have in our keyboard, in our note pad, image, video, audio is converted to binary and stored and retrieve back from binary 1s and 0s in a computer. This 0s and 1s are called bits are the state of a transistor either ON (1) or OFF (0). It can’t be both 0 and 1. For example a 1 MB memory must have 1024 *8=8192 transistors free to go any of the two states ON or OFF at a time.
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Audio may be converted to a wave form of a frequencies and amplitudes as numbers. Which numbers further converted to binary arrays. Now if these arrays are stored categorically it can be read in the same order to retrieve the same wave form in future. It is same with video and images where the conversion plays from light wave-length. Now it’s no more wonder that computer is nothing but a big calculator. Which is doing all these calculations with its millions of transistors.
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Argument stopped here with transistor. Engineers saying give me more and more transistors we will make powerful computers. Then the scientists see that there are some limits to making tiny transistor in a small chips and there are many really big calculations such as finding a vaccine for a virus, DNA mapping or red shift analyzing, many more. For such types of calculation to be done in a short time our classical computers will take many years to do a single calculation.
Then the scientists came with an idea to change the basic property (to represent a state, either 1 or 0) of the transistor. They started thinking to overcome the limit that one single transistor represent one state at a time. To make a transistor like device which can represent more than one state at a time we need to look out of the window. Here the quantum physics comes into play. Because quantum physics says a quantum system to be in multiple states at the same time until it is measured.
How much the Quantum computer enhancing the computing ability than a conventional computer:
Suppose a conventional tiny transistor of a 1-bit can represent 1-bit data either 1 or 0. Now suppose a quantum bit of 1 qubit that can represent 2-bit data. Thus it implies that in quantum bit can represent doubled bit data than the conventional bit. But it is not just doubled. The main game starts when we consider multi- qubits. Let’s understand, consider for 3 qubit quantum system. If we follow above example it should represent 2x3=6-bit data, it is wrong calculation. Remember 1 qubit processor can represent 2-bit data at the same time.
1-Qbit can represent 0 or 1 21=2 possibilities
2-Qbit can represent 00 01 10 11 22 =4 possibilities
3-Qbit Can represent 000 001 010 011 100 101 111 110 23 =8 possibilities
In the above we have seen the growth/capability is increasing exponentially @ 2n where n is no of Q-bit. Let’s make a simple calculator for addition of two 128 bits of input. For this we need a processor of 128 bits in conventional micro-transistor technologies. In quantum computing technologies we need a processor of only 7-Qbits (27 =128).
Now we can see the computing ability a quantum computer. However, quantum computer has exponentially powerful computing ability but it is very hard to maintain quantum system. Because quantum system/Q-bits are ultra-sensitive to external influence/energy. There are few things to understand how to quantum systems/Q-bits are created and maintained.
Quantum particles/system- To make use of quantum behavior and build a quantum computer we need to know which are the particles having quantum behavior. What is Quantum physics? The physics only for Quantum. What is Quantum? Quantum means Quanta. Quanta means the smallest possible parts of something? What is the smallest possible parts of matter? These are molecule, atom, electron, proton, neutron etc. Smallest parts of lights are photons etc. From above it implies that the Quantum particles are these tiny partials and Quantum physics is the physics of these tiny particles. The origin of quantum physics started from double slit experiment in 1801. The double slit experiment proves that though light is made of photon particles but flows in wave like nature. Further this experiment is done with other particles like electron, atom, molecule etc. All these particles showed same thing that when they flow, they flow like a wave. From this double slit experiment, it is concluded that particles at quantum level have wave like behavior when they are not observed, they appear as particle when they are observed. In studding of these particles nature, it comes into picture that these particles have behavior called superposition. In quantum computer we are interested in this particular behavior of these particles which can be used in representing huge no bits in a small no of Q-bits(explained above).
What is Quantum superposition- Heisenberg uncertainty principle states that it is impossible to know both position and speed of a particle such as photon or electron with perfect accuracy. This is because the particles movement is nearly in speed of light. Which further implies that these particles all states exist as possibilities at the same time. It appears in a particular state only when it observed. All though the above logics seem logically incorrect but these are experimentally proven by Quantum physicist (For reference you can see double slit experiment, electron double slit experiment, Quantum eraser double slit experiment etc.). This uncertainty of Quantum particle called Quantum superposition, became an advantage of computing in Quantum computer.
Quantum entanglement- It is the connection or link between two or more quantum particle so that the state of one particle is dependent to the others no matter how far the particles from each other. To understand it easy let’s take an example, suppose there is a pair of gloves I have to parcel each side to two persons A and B already know it. If package is delivered to A first, he opens it and found it of left hand. He instantly knows that B will receive right hand even if the package is not deliver to B yet. Here A and B are entangled we can say. Though it is not quantum entanglement. In practical how the quantum entanglement achieved-
a) Cooling and bringing particles close together- When particles are cooled near to absolute zero temperature, the particles comes close enough so that their quantum states overlap each other then it becomes difficult to distinguish them.
b) Subatomic processes- Subatomic process such as nuclear reactions where matter emits enormous amount of energies within a fraction of second- automatically generates entangled particles.
c) Splitting photons- Splitting a photon into two parts using crystal can create entangled photons.
d) Mixing photons- Photons can be mixed in a fiber-optic cable, this phenomenon can create an entangled photon pair.
Quantum interference- In quantum computing it is important and necessary to know and use quantum interference to get desired result in the output. As we know in the basis of quantum particles, that they have a nature of wave. This wave nature could be used and interfere with the input wave to get a suitable output.
In quantum computing inputs can be given in wave form which goes in to the quantum processor, interfere with the entangled qubits and gives an output in wave form. This interference is of mainly two types constructive and destructive interference.
Now we have some basic idea how the quantum computer is built and how they work. Let’s make a quantum computer which can add/subtract two numbers A and B bellow- Please note that bellow example is not how quantum computers built. This is just an assumption how it would be built. Let’s take 3 photons from a source. Again I want you clarify that bellow example is NOT how real quantum computers built as I am not expert of quantum computers. This is a simple assumption, how quantum computer would work.
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Conclusion:
Quantum computing is a wide window of possibility and hope. Quantum computing can solve huge complex computing in fastest ever which could take years for a conventional computer. It is still challenging to obtain hold quantum particles and measure the state. Scientist are still working to make easier those challenges. With the help of quantum computing we can solve many secrets of the universe and solve many unsolved problems in the field of health care, drug, cure of a disease etc.
FAQ:
1) What is an example of quantum computing?
Answer: Quantum Computers are distinguishing by the capability of computing complex data. For example, processing a complex data of huge number of distance stars send by an advanced telescope to find out habitable planets.
2) Is quantum computing part of AI?
Answer: AI is multi-layer software stack uses machine learning technique, which makes it more complex. Integrating AI with quantum computer makes it faster and powerful tough AI and quantum computing are different.
3) What is quantum computing basic concepts?
Answer: Quantum computing basic concept is to use superposition nature of quantum particles to represent 0 and 1 at the same time to enhance the computing capability exponentially.
4) Who is the father of quantum computing?
Answer: Father of quantum computing is David Deutsch FRS.
5) Is the human brain a quantum computer?
Answer: Human brain is not a quantum computer but human brain is very powerful when it is trained. It might not be replaceable with technological computing system yet.
