Friday 10 August 2018

WHAT IS ANTIMATTER

ANTI-MATTER :

Antimatter is the opposite of normal matter. More specifically, the sub-atomic particles of antimatter have properties opposite those of normal matter. The electrical charge of those particles is reversed. Antimatter was created along with matter after the Big Bang, but antimatter is rare in today's universe, and scientists aren't sure why.

Antimatter particles are created in ultra high-speed collisions. In the first moments after the Big Bang, only energy existed. As the universe cooled and expanded, particles of both matter and antimatter were produced in equal amounts. Why matter came to dominate is a question that scientists have yet to discover. 
One theory suggests that more normal matter was created than antimatter in the beginning, so that even after mutual annihilation there was enough normal matter left to form stars, galaxies and us. 

To better understand antimatter, one needs to know more about matter. Matter is made up of atoms, which are the basic units of chemical elements such as hydrogen, helium or oxygen. Each element has a certain number of atoms: Hydrogen has one atom; helium has two atoms; and so on.

In 1928, British physicist Paul Dirac wrote down an equation that combined quantum theory and special relativity to describe the behaviour of an electron moving at a relativistic speed. The equation – which won Dirac the nobel prize in 1933  – posed a problem: just as the equation x2=4 can have two possible solutions (x=2 or x=-2), so Dirac's equation could have two solutions, one for an electron with positive energy, and one for an electron with negative energy. But classical physics (and common sense) dictated that the energy of a particle must always be a positive number.
Dirac interpreted the equation to mean that for every particle there exists a corresponding antiparticle, exactly matching the particle but with opposite charge. For the electron there should be an "anti -electron", for example, identical in every way but with a positive electric charge. The insight opened the possibility of entire galaxies and universes made of antimatter.
WHAT IS QUARK ?

A quark is a fundamental particle which possesses both electric charge and 'strong' charge. They combine in groups of two or three to form composite objects (called mesons and baryons, respectively), held together by the strong force. Protons and neutrons are familiar examples of such composite objects -- both are made up of three quarks. 

Quarks and Lepton  are the building blocks which build up matter, i.e., they are seen as the "elementary particles". In the present standard model, there are six "flavors" of quarks. They can successfully account for all known mesons and Baryons  (over 200). The most familiar baryons are the Proton and Neutron , which are each constructed from up and down quarks. Quarks are observed to occur only in combinations of two quarks (mesons), three quarks (baryons). There was a recent claim of observation of particles with five quarks (pentaquark), but further experimentation has not borne it out.

WHAT IS ANTI-QUARK ?

Anti quark is the opposite of quark.the spins ,the charge are same but its a opposite of QUARK.

A anti-quark is a fundamental particle WHICH BUILD UP ANTI MATTER.


Antimatter spaceship?


When antimatter particles interact with matter particles, they annihilate each other and produce energy. This has led engineers to speculate that antimatter-powered spacecraft might be an efficient way to explore the universe.



it takes about $100 billion to create a milligram of antimatter. While research can get by on a lot less antimatter, this is the minimum that would be needed for application. 


"To be commercially viable, this price would have to drop by about a factor of 10,000," the agency wrote. Power generation creates another headache: "It costs far more energy to create antimatter than the energy one could get back from an antimatter reaction."





The design calls for pellets of Deuterium and tritium (heavy hydrogen isotopes with one or two neutrons in their nuclei, unlike common hydrogen that has no neutrons). An antiproton beam would then be beamed into the pellets, which would bash against a layer of uranium embedded inside. 


After the antiprotons strike the uranium, both would be destroyed and create fission products that would spark a fusion reaction. Properly directed, this could make a spacecraft move.

Monday 6 August 2018

DOES TIME END

Does time have a beginning?

Any universal concept of time must ultimately be based on the evolution of the cosmos itself. When you look up at the universe you're seeing events that happened in the past – it takes light time to reach us. In fact, even the simplest observation can help us understand cosmological time: for example the fact that the night sky is dark. If the universe had an infinite past and was infinite in extent, the night sky would be completely bright – filled with the light from an infinite number of stars in a cosmos that had always existed.







For a long time scientists, including Albert Einstein, thought that the universe was static and infinite. Observations have since shown that it is in fact expanding, and at an accelerating rate. This means that it must have originated from a more compact state that we call the Big Bang, implying that time does have a beginning. In fact, if we look for light that is old enough we can even see the relic radiation from Big Bang – the cosmic microwave background [CMB] . Realising this was a first step in determining the age of the universe
Time's arrow


So we know time most likely started during the Big Bang. But there is one nagging question that remains: what exactly is time?







To unpack this question, we have to look at the basic properties of space and time. In the dimension of space, you can move forwards and backwards; commuters experience this everyday. But time is different, it has a direction, you always move forward, never in reverse. So why is the dimension of time irreversible? This is one of the major unsolved problems in physics.


Imagine a box of gas in which all the particles were initially placed in one corner (an ordered state). Over time they would naturally seek to fill the entire box (a disordered state) – and to put the particles back into an ordered state would require energy. This is irreversible. It's like cracking an egg to make an omelette – once it spreads out and fills the frying pan, it will never go back to being egg-shaped. It's the same with the universe: as it evolves, the overall entropy increases.




AN EXAMPLE OF ENTROPY 


It turns out entropy is a pretty good way to explain time's arrow. And while it may seem like the universe is becoming more ordered rather than less – going from a wild sea of relatively uniformly spread out hot gas in its early stages to stars, planets, humans and articles about time – it's nevertheless possible that it is increasing in disorder. That's because the gravity associated with large masses may be pulling matter into seemingly ordered states – with the increase in disorder that we think must have taken place being somehow hidden away in the gravitational fields. So disorder could be increasing even though we don't see it.


But given nature's tendency to prefer disorder, why did the universe start off in such an ordered state in the first place? This is still considered a mystery. Some researchers argue that the Big Bang may not even have been the beginning, there may in fact be "parallel universes " where time runs in different directions." 


DOES ANY END OF TIME ?


As far as astrophysicists can tell, the universe is expanding at an accelerating rate, and will likely continue to do so indefinitely. But now some physicists are saying that this theory, called eternal inflation, and its implication that time is endless pose a problem for scientists calculating the probability of any event occurring. In a recent paper, they calculate that time is likely to end within the next 5 billion years due to some type of catastrophe that no one alive at the time will witness.


To see that this is not merely a philosophical point, it helps to consider cosmological experiments, where the rules are less clear. For example, one would like to predict or explain features of the CMB [cosmic microwave background]; or, in a theory with more than one vacuum, one might wish to predict the expected properties of the vacuum we find ourselves in, such as the Higgs mass. This requires computing the relative number of observations of different values for the Higgs mass, or of the CMB sky. There will be infinitely many instances of every possible observation, so what are the probabilities? This is known as the 'measure problem' of eternal inflation.





One solution to this problem, the physicists explain, is to conclude that time will eventually end. Then there would be a finite number of events that occur, with the improbable events occurring less often than the probable events.

The timing of this "cutoff" would define the set of allowed events. Thus, the physicists have attempted to calculate the probability of when time will end given five different cutoff measures. In two of these scenarios, time has a 50% chance of ending within 3.7 billion years. In two other scenarios, time has a 50% chance of ending within 3.3 billion years.

In the fifth and final scenario, the timescale is very short (on the order of the Planck time). In this scenario, the scientists calculated that "time would be overwhelmingly likely to end in the next second." Fortunately, this calculation predicts that most observers are "Boltzmann babies" who arise from quantum fluctuations in the early universe. Since most of us are not, the physicists could rule this scenario out "at a high level of confidence."

What would the end of time be like for observers around at the time? As the physicists explain, the observers would never see it coming. "The observer will necessarily run into the cutoff before observing the demise of any other system," the scientists write. They compare the boundary of the time cutoff to the horizon of a black hole.

The boundary ... can be treated as an object with physical attributes, including temperature, the authors write in their paper. Matter systems that encounter the end of time are thermalized at this horizon. This is similar to an outside observer's description of a matter system falling into a black hole. What is radically new, however, is the statement that we might experience thermalization upon crossing the black hole horizon. Yet the thermalizing "matter system" would still not notice anything unusual when crossing this horizon.

For those who feel uncomfortable about time ending, the physicists note that there are other solutions to the measure problem. They don't claim that their conclusion that time will end is correct, only that it follows logically from a set of assumptions. So perhaps one of the three assumptions underlying the conclusion is incorrect instead.

The first assumption is that the universe is eternally inflating, which is a consequence of general relativity and well supported by the experimental evidence so far observed. The second assumption is that the definition of probability is based on the relative frequency of an event, or what the scientists call the assumption of typicality. The third assumption is that, if spacetime is indeed infinite, then the only way to determine the probability of an event is to restrict one's attention to a finite subset of the infinite multiverse. Some other physicist have already looked into alternatives to this third assumption.







Tuesday 31 July 2018

QUANTUM LOGIC GATE

Quantum Logic Gates :

Traditional computers are like microscopic cities. The roads of these cities are wires with electricity coursing through them. These roads have lots of gates, known as logic gates, which enable computers to do their job. Like physical gates that allow or block cars, logic gates allow or block electricity. Electricity that goes through the gates represents a “1” of digital data, and blocked electricity is a “0.”
Logic gates are building blocks for processing information. One kind of logic gate, known as the AND gate, could, for example, quickly determine whether two people agree to a business deal. It takes in two bits of information, and generates a 1 if both incoming bits are 1 s. So, if both business people say “yes” (1) to the deal, the AND gate will output 1. If one or both say “no” (0), the AND gate generates a 0 or a no.
By arranging gates in a circuit, engineers can create something akin to a flowchart that enables computers to carry out many kinds of logical operations, such as mathematical calculations and perform the kinds of tasks that computers can do.
In their quantum logic gate, BY controlle the energy levels in an individual ion so that a lower-energy state represented a 0 and a higher-energy state represented a 1. The ion’s internal energy was the first q bit. They created a second quantum bit with the atom’s external motion: 0 represented less motion and 1 represented a greater amount of motion.

The group entangled the ion’s internal energy state with its overall motion. In the process, they made a quantum version of a CONTROLLED NOT gate. In their gate, the ion’s energy of motion serves the “control” bit. If it is a 1, then it causes the ion’s internal energy state to flip.

Quantum gates are usually represented as matrices. A gate which acts on k qubits is represented by a 2k x 2k unitary matrix. The number of qubits in the input and output of the gate have to be equal. The action of the gate on a specific quantum state is found by multiplying the vector which represents the state by the matrix representing the gate. In the following, the vector representation of a single qubit is:

Hadamard (H) gate
The hadamard gate is the one-qubit version of the quantum furier trasform..
Since  where I is the identity matrix, H is indeed a unity matrix.

Pauli-X gate



The Pauli-X gate acts on a single qubit. It is the quantum equivalent of the NOT gate for classical computers (with respect to the standard basis 


 which privileges the Z-direction) . It equates to a rotation of the bloch spare around the X-axis by pai radians. I Due to this nature, it is sometimes called bit flip.It is represented by the pauli metrix

Pauli-Y gate

The Pauli-Y gate acts on a single qubit. It equates to a rotation around the Y-axis of the Bloch sphere by pai radians. 
.

Pauli-Z gate

The Pauli-Z gate acts on a single qubit. It equates to a rotation around the Z-axis of the Bloch sphere by  radians. Thus, it is a special case of a phase shift gate (which are described in a next subsection) with . It leaves the basis state  unchanged and maps  to . Due to this nature, it is sometimes called phase-flip. It is represented by the pauli Z matrix:
.

Square root of NOT gate (NOT)

The NOT gate acts on a single qubit. so this gate is a square root of the NOT gate.

Similar squared root-gates can be constructed for all other gates by finding the unitary matrix that, multiplied by itself, yields the gate one wishes to construct the squared root gate of. All rational exponents of all gates can be created in this way. (Only approximations of irrational exponents are possible to synthesize from composite gates whose elements are not themselves irrational, since exact synthesis would result in infinite gate depth.)

Phase shift () gates

This is a family of single-qubit gates that leave the basis state  unchanged and map  to  The probability of measuring a  or  is unchanged after applying this gate, however it modifies the phase of the quantum state. This is equivalent to tracing a horizontal circle (a line of latitude) on the Bloch sphere by  radians.
where the phase shift. Some common examples are the  gate (commonly written as T) where , the phase gate (written S, though S is sometimes used for SWAP gates) where and the Pauli-Z gate where.

Swap (SWAP) gate

.
The swap gate swaps two qubits.


 With respect to the basis, it is represented by the matrix:

Square root of Swap gate (SWAP)



The sqrt(swap) gate performs half-way of a two-qubit swap. It is universal such that any quantum many qubit gate can be constructed from only sqrt(swap) and single qubit gates. 


The sqrt(swap) gate is not, however maximally entangling, more than one application of it is required to produce a Bell state from product states.

Controlled (cX cY cZ) gates

Controlled gates act on 2 or more qubits, where one or more qubits act as a control for some operation. For example, the controlled NOT gate (or CNOT or cX) acts on 2 qubits, and performs the NOT operation on the second qubit only when the first qubit is , and otherwise leaves it unchanged. With respect to the basis, it is represented by the matrix:

More generally if U is a gate that operates on single qubits with matrix representation
then the controlled-U gate is a gate that operates on two qubits in such a way that the first qubit serves as a control. It maps the basis states as follows.
The matrix representing the controlled U is




The CNOT gate is generally used in quantum computing to generate entangled states.When U is one of the pauli matrices, σx, σy, or σz, the respective terms "controlled-X", "controlled-Y", or "controlled-Z" are sometimes used.

Toffoli (CCNOT) gate



The Toffoli gate, also CCNOT gate or Deutsch  gate, is a 3-bit gate, which is universal for classical computation. The quantum Toffoli gate is the same gate, defined for 3 qubits. If the first two bits are in the state, it applies a Pauli-X (or NOT) on the third bit, else it does nothing. It is an example of a controlled gate. Since it is the quantum analog of a classical gate, it is completely specified by its truth table. The Toffoli gate is universal when combined with the single qubit Hadamard gate.


Fredkin (CSWAP) gate


The Fredkin gate (also CSWAP or cS gate) is a 3-bit gate that performs a controlled swap. It is universal for classical computation. It has the useful property that the numbers of 0s and 1s are conserved throughout, which in the billiard ball model means the same number of balls are output as input.

Ising (XX) gate

The Ising gate (or XX gate) is a 2-qubit gate that is implemented natively in some trapped-ion quantum computers. It is defined as

Deutsch gate

Deutsch  gate is a three-qubit gate. It is defined as
Unfortunately, a working Deutsch gate has remained out of reach, due to lack of a protocol. However, a method was proposed to realize such  with dipole-dipole interaction in neutral atoms.

Monday 30 July 2018

DIGITAL LOGIC GATES



Digital Logic | Logic Gates :


In Boolean Algebra, there are three basic operations,  which are analogous to dis-junction, conjunction, and negation in propositional logic. Each of these operations has a corresponding logic gate. Apart from these there are a few other logic gates as well.
Digital logic gates may have more than one input, (A, B, C, etc.) but generally only have one digital output, (Q). Individual logic gates can be connected together to form combinational or sequential circuits, or larger logic gate functions.
Integrated Circuits or IC’s as they are more commonly called, can be grouped together into families according to the number of transistors or “gates” that they contain. For example, a simple AND gate my contain only a few individual transistors, were as a more complex microprocessor may contain many thousands of individual transistor gates. Integrated circuits are categorised according to the number of logic gates or the complexity of the circuits within a single chip with the general classification for the number of individual gates given as:
Logic Gates –
  • AND gate(.) – The AND gate gives an output of 1 if both the two inputs are 1, it gives 0 otherwise.
  • OR gate(+) – The OR gate gives an output of 1 if either of the two inputs are 1, it gives 0 otherwise.
NOT gate(‘) – The NOT gate gives an output of 1 input is 0 and vice-versa.
  • XOR gate(⊕) – The XOR gate gives an output of 1 if either both inputs are different, it gives 0 if they are same.
Three more logic gates are obtained if the output of above-mentioned gates is negated.



  • NAND gate(↑)- The NAND gate (negated AND) gives an output of 1 if both inputs are 0, it gives 1 otherwise.
  • NOR gate(↓)- The NOR gate (negated OR) gives an output of 1 if both inputs are 0, it gives 1 otherwise.
XNOR gate(⊙)- The XNOR gate (negated XOR) gives an output of 1 both inputs are same and 0 if both are different.

Boolean Algebra :

Boolean Algebra is used to analyze and simplify the digital (logic) circuits. It uses only the binary numbers i.e. 0 and 1. It is also called as Binary Algebra or logical Algebra

Following are the important rules used in Boolean algebra.
1.   Variable used can have only two values. Binary 1 for HIGH and Binary 0 for LOW.2.   Complement of a variable is represented by an overbar (-).
3.  ORing of the variables is represented by a plus (+) sign between them. For example ORing of A, B, C is represented as A + B + C.
4.  Logical ANDing of the two or more variable is represented by writing a dot between them such as A.B.C. Sometime the dot may be omitted like ABC.

Digital Logic States :

The Digital Logic Gate is the basic building block from which all digital electronic circuits and microprocessor based systems are constructed from. Basic digital logic gates perform logical operations of ANDOR and NOT on binary numbers.
In digital logic design only two voltage levels or states are allowed and these states are generally referred to as Logic “1” and Logic “0”High and Low, or True and False. These two states are represented in Boolean Algebra and standard truth tables by the binary digits of “1” and “0” respectively
Most digital logic gates and digital logic systems use “Positive logic”, in which a logic level “0” or “LOW” is represented by a zero voltage, 0v or ground and a logic level “1” or “HIGH” is represented by a higher voltage such as +5 volts, with the switching from one voltage level to the other, from either a logic level “0” to a “1” or a “1” to a “0” being made as quickly as possible to prevent any faulty operation of the logic circuit.
Every Logic gate has a graphical representation or symbol associated with it. Below is an image which shows the graphical symbols and truth tables associated with each logic gate.

Logic AND Gate :

Logic AND Gate is a type of digital logic gate whose output goes HIGH to a logic level 1 when all of its inputs are HIGH.
The output state of a “Logic AND Gate” only returns “LOW” again when ANY of its inputs are at a logic level “0”. In other words for a logic AND gate, any LOW input will give a LOW output.
The logic or Boolean expression given for a digital logic AND gate is that for Logical Multiplication which is denoted by a single dot or full stop symbol, ( . ) giving us the Boolean expression of:  A.B = Q.

Logic OR Gate :

Logic OR Gate is a type of digital logic gate whose output goes HIGH to a logic level 1 when one or more of its inputs are HIGH.
The output, Q of a “Logic OR Gate” only returns “LOW” again when ALL of its inputs are at a logic level “0”. In other words for a logic OR gate, any “HIGH” input will give a “HIGH”, logic level “1” output.
The logic or Boolean expression given for a digital logic OR gate is that for Logical Addition which is denoted by a plus sign, ( + ) giving us the Boolean expression of:  A+B = Q.

Exclusive-OR Gate :

The Exclusive-OR logic function is a very useful circuit that can be used in many different types of computational circuits.
In the previous tutorials, we saw that by using the three principal gates, AND Gate, the OR Gate and the NOT Gate, we can build many other types of logic gate functions, such as a NAND Gate and a NOR Gate or any other type of digital logic function we can imagine.
But there are two other types of digital logic gates which although they are not a basic gate in their own right as they are constructed by combining together other logic gates, their output Boolean function is important enough to be considered as complete logic gates. These two “hybrid” logic gates are called the Exclusive-OR (Ex-OR) Gate and its complement the Exclusive-NOR (Ex-NOR) Gate.
Previously, we saw that for a 2-input OR gate, if A = “1”OR B = “1”OR BOTH A + B = “1” then the output from the digital gate must also be at a logic level “1” and because of this, this type of logic gate is known as an Inclusive-OR function. The gate gets its name from the fact that it includes the case of Q = “1” when both A and B = “1”.
If however, an logic output “1” is obtained when ONLY A = “1” or when ONLY B = “1” but NOT both together at the same time, giving the binary inputs of “01” or “10”, then the output will be “1”. This type of gate is known as an Exclusive-OR function or more commonly an Ex-Or function for short. This is because its boolean expression excludes the “OR BOTH” case of Q = “1” when both A and B = “1”.
In other words the output of an Exclusive-OR gate ONLY goes “HIGH” when its two input terminals are at “DIFFERENT” logic levels with respect to each other.
An odd number of logic “1’s” on its inputs gives a logic “1” at the output. These two inputs can be at logic level “1” or at logic level “0” giving us the Boolean expression of:  Q = (A ⊕ B) = A.B + A.B
The Exclusive-OR Gate function, or Ex-OR for short, is achieved by combining standard logic gates together to form more complex gate functions that are used extensively in building arithmetic logic circuits, computational logic comparators and error detection circuits.

Logic NAND GATE :

The Logic NAND Gate is a combination of a digital logic AND gate and a NOT gate connected together in series.
The logic or Boolean expression given for a logic NAND gate is that for Logical Addition, which is the opposite to the AND gate, and which it performs on the complements of the inputs. The Boolean expression for a logic NAND gate is denoted by a single dot or full stop symbol, ( . ) with a line or Overline, ( ‾‾ ) over the expression to signify the NOT or logical negation of the NAND gate giving us the Boolean expression of:  A.B = Q.


Logic NOR Gate :

The Logic NOR Gate gate is a combination of the digital logic OR gate and an inverter or NOT gate connected together in series
The logic or Boolean expression given for a logic NOR gate is that for Logical Multiplicationwhich it performs on the complements of the inputs. The Boolean expression for a logic NOR gate is denoted by a plus sign, ( + ) with a line or Overline, ( ‾‾ ) over the expression to signify the NOT or logical negation of the NOR gate giving us the Boolean expression of:  A+B = Q.

Exclusive-NOR Gate :

The Exclusive-NOR Gate function is a digital logic gate that is the reverse or complementary form of the Exclusive-OR function.
Basically the “Exclusive-NOR Gate” is a combination of the Exclusive-OR gate and the NOT gate but has a truth table similar to the standard NOR gate in that it has an output that is normally at logic level “1” and goes “LOW” to logic level “0” when ANY of its inputs are at logic level “1”.
However, an output “1” is only obtained if BOTH of its inputs are at the same logic level, either binary “1” or “0”. For example, “00” or “11”. This input combination would then give us the Boolean expression of:  Q = (A ⊕ B) = A.B + A.B

WHAT IS ANTIMATTER

ANTI-MATTER : Antimatter is the opposite of normal matter. More specifically, the sub-atomic particles of antimatter have properties ...