# ABOUT QUANTUM MECHANICS AND MOLECULAR ELECTRONICS

**ABOUT QUANTUM MECHANICS AND MOLECULAR ELECTRONICS :**

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**ABOUT QUANTUM MECHANICS : **

Quantum mechanics, developed by German scientist Werner Heisenberg, is a set of scientific principles which explain how matter interacts with energy and the importance of this phenomenon in our everyday life.

Quantum mechanics is the study of behaviour of matter at the microscopic level, somewhat related to the study of atomic and subatomic particles. It is included in the microscopic domain of physical mechanics.

Towards the beginning of the 20^{th} century, scientists discovered that some phenomenon occurring in both the macro and micro world could not be explained with classical mechanics only.

The very discovery of these limitations of Newtonian Mechanics or classical mechanics led to the development of a new domain, named Quantum Mechanics. The credit for developing the first quantum theory goes to max Planck who was also awarded the noble prize for the same in 1918.

However it was Albert Einstein who first suggested that quantisation could not be just a mathematical trick and explained the laws of a most popular theory The Photoelectric Effect. Later in 1913, Neils Bohr introduced a new model of the atom which involved quantised electron orbits.

Max Planck gave the first model to explain the full spectrum of thermal radiation in the year 1900. The relation between the Planck’s constant and energy, frequency is given by:

**E=nhf, where n=1,2,3…..**

In the year 1887, H. hertz had discovered the photo electric effect. Einstein explained this effect by suggesting that if the beam of light is of frequency f, then each photon is likely to possess energy equal to hf.

Toward the first half of the 20^{th} century, it was known that atoms were made from a cloud of negatively charged electrons arranged around a positively charged nucleus with protons and neutrons.

Applications of quantum mechanics involve magnetic resonance imaging and the laser. All in all, this field is an important part in the study of mechanics in physics.

**HISTORY OF MOLECULAR ELECTRONICS :**

The study and applications of molecular building blocks electronic profitably offers the control of properties at molecular level, it has generated much excitement among researchers. The semiconductor industry was responsible for manufacturing micro electric components, before nanotechnology came into use. As late as the 1950’s, the industries’ main material has been silicon.

Therefore it is impossible to understand the semi conductor industry without having knowledge of its alternatives, since research communities that form the backbone of nanotechnology are devoted to perfect the existing industry. Toward the second half of the 20^{th} century, molecular electronics gained pace as a visionary program conducted on behalf of Air Force. Then again it reappeared at IBM in 1970 and finally at the naval research laboratory in 1980. Only towards the ending part of the 20^{th} century, with the help of nanotechnology, has molecular electronics neared acceptance by the semiconductor industry.

**MOLECULAR SCALE ELECTRONICS :**

Single molecule electronics also called as Molecular Scale Electronics belongs to nanotechnology branch and this uses single molecules as its components . these molecules contain stable structures that are too small and this helps in fulfilling the final goal that is in contraction of electrical circuits. This is called molecular electronics and this uses the molecular properties to affect the bulking properties of various materials. This property of materials is replaced by single molecules in molecular electronics . The molecular scale electronics is created by combining the atoms together while controlling the composition of molecules to the last atom .

An open quantum system is used in single molecule devices and the non equilibrium molecular junction is avoided. By using the equilibrium structure of electronic system the current-voltage can be calculated. Some examples of molecular scale electronics are Diodes, Transistors and electrical wires. Hence single molecule electronics is used because; in this the electrons move freely and easily in a closed area by delocalizing the molecular orbital. Although there are many applications of molecular scale electronics, some common hindrance are commercialization, artefacts and isolated state of molecules.

**IMPLEMENTATION OF QUANTUM COMPUTER :**

A quantum computer which uses quantum mechanics directly is called quantum computer. Quantum computers require quantum properties to represent the data and process their data. Quantum computer are very similar to deterministic and probabilistic computers. Some application of Quantum computers are :

- They use various algorithms to solve problems and hence it is much faster than any traditional computer.
- It uses Simon’s algorithm which is faster than all other algorithms .
- They help in making efficient searches
- They are mostly used in solving linear equations that can solve complex calculations like the weather systems.

An implementation method of quantum computation is spatial coding. The quantum information is represented by the intensity and phase of cells .

**QUANTUM ALGORITHM :**

A quntum algorithm is required for quantum computation . a quantum algorithm can be defined as a sequence of instructions which can be solved in a step by step procedure and each step is processed by a quantum computer. These algorithms follow the properties of quantum superposition and entanglement .they can solve problems faster than that of classical algorithms. They use various techniques like fourier transform , topological quantum field theory etc.

The algorithms that depends on quantum fourier transform techniques are Deutsch-Jozsa algorithm and Simon’s algorithm .

Deutsch-Jozsa algorithm helps in solving exactly one query to a black box problem through a quantum computer .

Simon’s algorithm helps in solving the black box problem faster than any other classical algorithm .

The quantum algorithm that depends on amplitude amplification techniques are Grover’s algorithm and Quantum counting .

Grover’s algorithm can solve only O(n)^2 queries by searching for unstructured data having n entries

Quantum counting are used to solve search problems. It detects and solves the problem of counting the number of marked entries in an unstructured database.

**QUANTUM GATES AND CIRCUITS : **

A Quantum logic gate is defined as a quantum circuit operating on number of qubits . They are reversible unlike other classical logic gates . Some commonly used gates are swap gate , poly shift gates , poly X-gate etc .

A quantum circuit may be a model for quantum computation .Computation is a series of quantum gates . Theoritically there are not many difference between a reversible n bit circuit and n bit logical gate . however a small number of reversible gates that can be assembled are easier to deal with. This scheme is called classical assembly .

**QUESTIONS AND ANSWERS :**

- DEFINE QUANTUM MECHANICS ?

ANS> Quantum mechanics, developed by German scientist Werner Heisenberg, is a set of scientific principles which explain how matter interacts with energy and the importance of this phenomenon in our everyday life.

Quantum mechanics is the study of behaviour of matter at the microscopic level, somewhat related to the study of atomic and subatomic particles. It is included in the microscopic domain of physical mechanics.

Towards the beginning of the 20^{th} century, scientists discovered that some phenomenon occurring in both the macro and micro world could not be explained with classical mechanics only.

The very discovery of these limitations of Newtonian Mechanics or classical mechanics led to the development of a new domain, named Quantum Mechanics. The credit for developing the first quantum theory goes to max Planck who was also awarded the noble prize for the same in 1918.

However it was Albert Einstein who first suggested that quantisation could not be just a mathematical trick and explained the laws of a most popular theory The Photoelectric Effect. Later in 1913, Neils Bohr introduced a new model of the atom which involved quantised electron orbits.

Max Planck gave the first model to explain the full spectrum of thermal radiation in the year 1900. The relation between the Planck’s constant and energy, frequency is given by:

E=nhf, where n=1,2,3…..

2. WHAT IS THE HISTORY OF MOLECULAR ELECTRONICS ?

ANS> The study and applications of molecular building blocks electronic profitably offers the control of properties at molecular level, it has generated much excitement among researchers. The semiconductor industry was responsible for manufacturing micro electric components, before nanotechnology came into use. As late as the 1950’s, the industries’ main material has been silicon.

Therefore it is impossible to understand the semi conductor industry without having knowledge of its alternatives, since research communities that form the backbone of nanotechnology are devoted to perfect the existing industry. Toward the second half of the 20^{th} century, molecular electronics gained pace as a visionary program conducted on behalf of Air Force. Then again it reappeared at IBM in 1970 and finally at the naval research laboratory in 1980. Only towards the ending part of the 20^{th} century, with the help of nanotechnology, has molecular electronics neared acceptance by the semiconductor industry.

3. WHAT IS QUANTUM ALGORITHM ? NAME SOME QUANTUM ALGORITHMS ?

ANS > A quantum algorithm is required for quantum computation . a quantum algorithm can be defined as a sequence of instructions which can be solved in a step by step procedure and each step is processed by a quantum computer. These algorithms follow the properties of quantum superposition and entanglement .they can solve problems faster than that of classical algorithms. They use various techniques like fourier transform , topological quantum field theory etc.

The algorithms that depends on quantum fourier transform techniques are Deutsch-Jozsa algorithm and Simon’s algorithm .

Deutsch-Jozsa algorithm helps in solving exactly one query to a black box problem through a quantum computer .

Simon’s algorithm helps in solving the black box problem faster than any other classical algorithm .

The quantum algorithm that depends on amplitude amplification techniques are Grover’s algorithm and Quantum counting .

Grover’s algorithm can solve only O(n)^2 queries by searching for unstructured data having n entries

Quantum counting are used to solve search problems. It detects and solves the problem of counting the number of marked entries in an unstructured database.

**
**4. DEFINE MOLECULAR SCALE ELECTRONICS AND WHAT IS THE IMPLEMENTATION OF QUANTUM COMPUTER ?

ANS >Single molecule electronics also called as Molecular Scale Electronics belongs to nanotechnology branch and this uses single molecules as its components . these molecules contain stable structures that are too small and this helps in fulfilling the final goal that is in contraction of electrical circuits. This is called molecular electronics and this uses the molecular properties to affect the bulking properties of various materials. This property of materials is replaced by single molecules in molecular electronics . The molecular scale electronics is created by combining the atoms together while controlling the composition of molecules to the last atom .

An open quantum system is used in single molecule devices and the non equilibrium molecular junction is avoided. By using the equilibrium structure of electronic system the current-voltage can be calculated. Some examples of molecular scale electronics are Diodes, Transistors and electrical wires. Hence single molecule electronics is used because; in this the electrons move freely and easily in a closed area by delocalizing the molecular orbital. Although there are many applications of molecular scale electronics, some common hindrance are commercialization, artefacts and isolated state of molecules.

IMPLEMENTATION OF QUANTUM COMPUTER :

A quantum computer which uses quantum mechanics directly is called quantum computer. Quantum computers require quantum properties to represent the data and process their data. Quantum computer are very similar to deterministic and probabilistic computers. Some application of Quantum computers are :

- They use various algorithms to solve problems and hence it is much faster than any traditional computer.
- It uses Simon’s algorithm which is faster than all other algorithms .
- They help in making efficient searches
- They are mostly used in solving linear equations that can solve complex calculations like the weather systems.

An implementation method of quantum computation is spatial coding. The quantum information is represented by the intensity and phase of cells .

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