Quantum Computing Made Easy

Quantum computing opens a new world of possibilities. It has brought with it increased levels of thinking. It acts as a common language between the sciences: Math, Physics, Chemistry and Computers. It helps in easy solving of complex problems. It is used in secure communications. Overall, it is a biggest advance which changes the way we think of the universe.

Quantum Theory: -

The study of quantum theory started in early 1900’s. The theory was never complete or self-consistent. It was more of a generalized prescription. The improvement in study of quantum theory through the years can be seen by these statements given by great scientists.

Marvelous .what ideas the young people have these days. But I don’t believe a word of it.

------Albert Einstein

I myself only came to believe in the uncertainty relations after many pangs of conscience…

------Werner Heisenberg

Anyone who is not shocked by quantum theory has not understood a single word.

------Neils Bohr

What is a Quantum Computing?

Quantum computing is the method in which the quantum properties are used to represent data and perform operations on these data.

What is quantum computer?

A quantum computer is a device that makes use of the quantum mechanical properties for computation and to perform operations on data.

“A quantum computer is to a regular computer, what a laser is to a lightbulb.”

--Seth Lloyd, MIT

What are quantum mechanical properties?

The laws such as Quantum superposition and entanglement are called as the quantum mechanical properties. Quantum mechanics is a set of scientific principles describing the known behavior of energy and matter that predominate at the atomic and subatomic scales. The name derives from the observation that some physical quantities such as the energy of an electron can be changed only by set amounts, or quanta, rather than being capable of varying by any amount.

How different is a quantum computer from a normal computer?

Currently the computer chips are filled with the gates which have width of few fractions of microns. In quantum computing the gates will move to the atomic level. At the atomic level matter obeys rules of quantum mechanics. This provides two advantages of using the quantum computer:-

1. Allows complete new algorithms which help in faster computations.

2. It is better than cramming more and more gates on a chip.

The Basics of Quantum Computing:-

1. An atom, not an electron ; is the physical bit

2. An electron is 0 or 1

3. An atom can be 0,1 or both

4. The bit in quantum mechanics is a QUBIT.

What’s the difference?

n bits can store one of 2ⁿ numbers at any time

n qubits can store all 2ⁿ numbers at once

The advantages of qubits: -

1. Adding qubits increases storage exponentially

2. Can do operations on all superpositions; like parallel computation.

--> One math operation on 2ⁿ numbers encoded with n bits requires 2ⁿ steps or 2ⁿ parallel processors.

-->The same operation on 2ⁿ numbers encoded by n qubits take 1 step.

3. This makes complex problems easier.

Example: Factoring

1. As the number of digits increase the factoring takes longer.

2. Increasing CPU speed only increases calculation linearly.

3. Factoring 1000 digits number classically would take longer than the lifetime of universe.

4. Quantum computers do this in minutes.

Example: - Cryptography

RSA cryptography relies on the difficulty of factoring large numbers to be secure…

Quantum Cryptography

1. To break RSA a hacker would need a large scale quantum computer (10,000 qubits).

2. Quantum computing offers new possibilities for secure communication.

2. a. Entanglement: - Two quantum bits when combined for a purpose perform better than two normal bits

2. b. Teleportation: - Two entangled objects can only be known by their “owners”.

3. Entangled atoms are used as keys.

Troubles to work out: -

1. Must reduce decoherence i.e the computation spreads beyond local computers and effects other qubits. Qubits must only interact with themselves, not their environment.

2. Current quantum computers have as few as around 10 qubits. 1000’s of qubits would be ideal.

Future of Quantum computing

1. It can be used for better cryptography.

2. A molecular computer becomes a possibility.

3. It will surely be able to solve problems, which are not quite problems yet.