Pratik Barve, Author at PhysicStuff

What is the difference between classical and quantum computer?

By Pratik Barve | September 21, 2017 | Comments 0 Comment

Classical computers which we use in our day to day life uses bits that is 0’s and 1’s also known as binary language to process data. Every character, number, special characters, are defined by ASCII code which is followed by classical computers. The processor which is main component in a computer is made up of billions of transistors which turn on and off in sync to transmit and process data. Billions of transistors on such a small chip! Imagine how small each transistor is in a processor.
Moores law states that the number of transistors on a chip doubles every 18 months. So now we are actually approaching the limit a transistor can be shrunk. A transistor is made up of junctions and as the transistors are becoming smaller the width of junction is approaching the atomic scale, currently the latest processors have the junction width of few tens of atoms. If we shrink the transistor more quantum effects like quantum tunneling comes into play. So there will come a point when reducing the size of transistors is not possible.

Traditional computer chips contain millions of transistors in a small area.

Quantum computers use quantum mechanical phenomenon like superposition and entanglement. The major difference between classical and quantum computers is that they use qubits over bits. Bits are 0’s and 1’s that is on state or off state. These both states are well defined. A single qubit can represent a one, a zero, or any quantum superposition of those two qubit states; a pair of qubits can be in any quantum superposition of 4 states, and three qubits in any superposition of 8 states. In general, a quantum computer with n qubits can be in an arbitrary superposition of up to 2^{n} different states simultaneously (this compares to a normal computer that can only be in one of these 2^{n} states at any one time). A quantum computer operates on its qubits using quantum gates and measurement (which also alters the observed state). That is we cannot observe the quantum process as observing it would collapse the process and it would be just like any other classical computer.

Physical representation of a qubit is any system or particle having 2 quantum states. For example an electron can be a qubit with spin up as one state and spin down as other state, superposition of these two states is also possible in a qubit as mentioned before. Other physical implementations of qubits are : Photons, Nucleus, Optical lattice, Josephson Junction, Quantum dot etc. So if we cannot observe the quantum process how do we manipulate qubits to get the desired output? For this we use the phenomenon of quantum entanglement, in simple words pairs or system of particles are in the same quantum state but away from each other.Measurements of physical properties such as position, momentum, spin, and polarisation, performed on entangled particles are found to be appropriately correlated.

One more important thing that may cause a disturbance in quantum computing is Quantum Decoherence. In quantum mechanics particles such as electrons are described by wave functions. If a quantum system is not perfectly isolated but is in contact with the surrounding then the quantum behaviour is lost. Decoherence can be viewed as loss of information to the surrounding. The superimposed wave functions acquire phases from their immediate surrounding.

This is a very active and wide field of research and lot of development is needed to make quantum computing practical. Some benefits of quantum computing are that more number of operations can be done at the same time in parallel way, large-scale quantum computers would theoretically be able to solve certain problems much more quickly than any classical computers that use even the best currently known algorithms, they can be used for research in genetics as it requires rigorous analysis, etc. The quantum realms are deep and unexplored and wonderful things happen at quantum level.

Bruno a born rebel.

By Pratik Barve | September 3, 2017 | Comments 0 Comment

Imagine the world before telescopes, when the universe was only what you could see through the naked eye. It seemed like our planet Earth was motionless and everything including the sun, the moon, planets and stars revolved around us making ‘US’ the centre of the universe. And then a Polish astronomer Copernicus made a radical proposal that Earth was not the centre of the universe. It was just one of the planets that revolved around the sun. This was not accepted back then as it was against the scripture (Bible).

Giordano Bruno was a young Dominican monk in Naples, and a natural born rebel. There was a time when there was no freedom of thought. Bruno was curious about the God’s creation. He dared to read the books banned by church. He came across a very old book titled ‘On the nature of things’ by Lucretius. In that book Lucretius asked the reader, to imagine standing at the edge of the universe and shooting an arrow outward. If the arrow keeps going, then clearly the universe extends beyond what we thought was the edge. But if the arrow doesn’t keep going, say it hits a wall or some boundary, then that wall must lie beyond what we thought was the edge of the universe. Now stand on that wall and shoot another arrow, there are same two possible outcomes, it either flies for ever or hits another boundary where we can shoot yet another arrow. Either way the universe is unbounded. The cosmos must be infinite. This made perfect sense to Bruno, the God he worshiped was Infinite!

Bruno became an evangelist, spreading the gospel of infinity throughout Europe. He thought that other lovers of God would naturally embrace the idea of an infinite universe as it is grander view. He was excommunicated by the Roman Catholic Church in his homeland, expelled by the Calvinists in Switzerland, expelled by Lutherans in Germany. He couldn’t keep his soaring vision of the cosmos to himself, despite the fact that the penalty for doing so in his world was the most vicious form of cruel and unusual punishment. Giordano Bruno lived at a time when there was no such thing as the separation of church and state or the notion that freedom of speech was a sacred right of every individual. Expressing an idea that didn’t conform to traditional belief could land you in deep trouble.

Recklessly Bruno returned to Italy. His homeland was one of the most dangerous places in Europe he could possibly go. The Roman Catholic Church maintained a system of courts known as the Inquisition and its sole purpose was to investigate and torment anyone who dared voice views that differed from theirs. He was languished in confinement for eight years. Through relentless interrogations he stubbornly refused to renounce his views. Why did the church go to such lengths to torment Bruno? What were they afraid of? If Bruno was right, then the sacred books and the authority of the Church would be open to question. He was turned over to the secular authorities. On Ash Wednesday, 17 February 1600, in the Campo de’ Fiori (a central Roman market square), with his “tongue imprisoned because of his wicked words”. He was hung upside down naked before he was finally burned at the stake.

Excerpt from the TV show Cosmos : A Spacetime Odyssey.

How did they think of the name ‘Google’?

By Pratik Barve | September 2, 2017 | Comments 3 comments

You may well have heard of a thing called the World Wide Web, and no doubt also of the remarkable search engine called ‘Google’ which has wrapped its tentacles around the information content of the world. Google is a curious name for a company that runs this huge computer-intensive search operation; its headquarter, the Googleplex, sounds even odder.

The story behind those names begins with an American mathematician, Edward Kasner who was a professor at Bernard College, Columbia University, in New York. In addition to his research work in different areas of mathematics to the general public and to young people through talks, books and articles. His most famous publication was the book ‘Mathematics and the Imagination’, which he wrote with James Newman, first published in 1940 and still in print today. One of the chapters dealt with very large numbers and gives an example of a neat- looking number that is enormously large: 10¹⁰⁰; that is 1 followed by 100 zeros. For comparison, there are only about 10⁸⁰ atoms and 10⁹⁰photons of light in the entire visible universe. In 1938 Kasner’s nine year old nephew, Milton Sirotta, invented the name Googol for this number and then coined the term Googolplex for the unimaginably larger number obtained by raising the googol to the power of ten, so:

1 Googolplex = 10^Googol

This number is so large that if we started to write it out in full as 10000000000….. it would not fit into the visible universe, which is only about 10²⁹ cm across.

The story told by the computer scientist David Koller is that back in 1996 two young computer science Ph.D. students at Stanford University, Larry Page and Sergey Brin, were starting to think about how they could map the network of interconnections between different pages containing common words and citations on the Web. Eventually, the strategy they developed to rank pages turned into the most effective internet search engine. At first they called this new search technology ‘Backrub’, but the following year they were trying to find a better name to reflect the huge number of links involved in the searches, and one of their fellow students, Sean Anderson, suddenly suggested Googolplex, which page shortened to Googol. This sounded like a good name so Anderson did a quick computer search to see if Googol.com was still available as a possible internet domain name. In his rush he mistypes the spelling as ‘Google.com’ and found that it was still available. Brin seemed to like the new (mis)spelling better than original and registered Google.com under Brin and Page’s names that very day, 15 September 1997. Later, when Google grew into a massive company, its remarkable headquarters building in Mountain View, Santa Clara, close to San Jose in California, was nicknamed ‘The Googleplex’.

An excerpt from the book ‘ The Book of Universes’ by John D. Barrow.