An Insight into Quantum Computing

An Insight into
Quantum Computing
Presented By
Shijin M S
Livares Technologies Pvt LtdTech&Socio-Cultural Group

Livares Technologies Pvt LtdLivares Technologies Pvt Ltd| Tech & Socio Cultural Group
Agenda
● What is quantum computing ?
● Why we need Quantum Computer ?
● Bit vs Qubit (Comparison)
● Quantum mechanics
● Qubit (detailed)
● Quantum Gates
● Building a Qubit with Phosphorus atom (video)
● Recent achievements and Quantum supremacy
● Limitations

Quantum Computing - It is an interaction of
Math, Physics and Computer science
Quantum computing takes
advantage of the strange
ability of subatomic particles
to exist in more than one
state at any time.
Due to the way the tiniest of
particles behave, operations
can be done much more
quickly than classical
computer
Exponential increase in
speed.

Why we need Quantum computers
Classical computers have achieved many things
E.g space mission, new medicines, simulation of an flight, even
reading your emotions
We don't usually talk about they can't do
E.g weather patterns, climate change, boosting AI training, data from stock market, drugs, brain
activity

Optimization
finding the best solution to the problem out of all
possible solutions
Machine learning
Weather
forecasting and
climate change

Dinner table example
You have 10 people over
for dinner, How many
ways can you configure 10
people around a table?
Answer is “10!”

Pioneers of Quantum Computer
● Introduced idea of Quantum mechanics in
computer
● Conference in MIT “PHYSICS ON
COMPUTING” on 1982
● We could perform calculation in parallel

Peter shor's Factorization algorithm
Prime Number Factorization
E.g. RSA numbers
RSA-768 =
123018668453011775513049495838496272077285356959533479219
732245215172640050726365751874520219978646938995647494277
4063845925192557326303453731548268
507917026122142913461670429214311602221240479274737794080
665351419597459856902143413
The CPU time spent on finding these factors by a collection of parallel
computers amounted approximately to the equivalent of almost 2000 years
of computing on a single-core 2.2 GHz AMD Opteron-based computer

Grover Algorithm
● For unordered list
● Used for database search

Why is the need to understand how a
particle behaves in quantum world?
● The smaller and smaller any particle
gets its quantum behavior will start
to dominate and classical physics
have no effect.
● Behaves like a wave
● Transistor usually have size of
22nm.
● Quantum annealing
● Atoms are at the size of 0.1 to 0.5nm

Bit vs Qubit
Bit is made up of tiny transistors and measured using voltage.
Qubit can be electron , atom , molecule if required environment persist. Usually made up of
electron from silicon
N = 2^n;
n = number of qubits
N = number of states.
Fascinating fact 2^300 is more than the particles in universe

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Bit can be only one
configurations at once
Qubit can be only multiple
configurations at once

Prerequisite
● Quantum Mechanics
● Quantum information overlap with AMO
● Condensed matter and high energy
● Linear Algebra
○ Matrix Multiplication**
● Partial Differential Equation
● Probability
● Random matrix theory and functional analysis
● Error correcting codes
● Electrical Engineering (for experiment)

Quantum mechanics: It's a powerful and
mysterious force of nature but weird !
It is branch of physics
Study of atomic and
subatomic particles
Wave Particle Duality
Quantum Superposition
Quantum Entanglement

It is a concept in Quantum
mechanics that every particle or
quantum entity may be described
as either a particle or a wave
Already proved using famous Double
Slit experiment more than 100 years
ago with light and electron
Wave-Particle Duality

Double slit experiment
This image clearly proves that
electron behaves like a wave

The curious case of Quantum
Superposition
It is the ability of a quantum system
to be in multiple states at the same
time until it is measured
Superposition is achieved in Qubit
using Hadamard Gate

Basically when we connect two
superpositioned Qubits we get
It's possible to teleport
Entanglement is achieved in Qubit
using Hadamard and Controlled
NOT gate (CNOT gate)

Qubit
● Spin up and spin down is used to measure 0 or 1 (electron)
● Vertically polarised or horizontally polarised (photon)
● Microwave pulse to control the spin
● Pure silicon atom is used. Nucleus of silicon has no spin , less magnetic field,
● Other atoms nucleus has a small amount of magnetic energy which determines the
electron spin or down.
● Should be kept in absolute temperature.

Four ways in which we can represent
Quantum Gates
Bra-Ket notation (Dirac notation)
Matrices and vectors (since most of the quantum gates operation are unitary operation)
Bloch sphere ( a visual representation)
Running the Quantum circuit through a measurement using Qiskit

Basics before we learn Quantum Gates
Representing classical bits as
vector
Matrix Multiplication

Basics before we learn Quantum Gates
Tensor product of vectors

Bloch Sphere

Quantum gates
● It uses Superposition, Entanglement and Reversible computing
● It will be represented in Basic linear Algebra(Vectors and Matrices)
● A qubit can be represented like this also collapse to 0 with probability of a^2 and 1
with probability of b^2
Qubits Representation in Superposition

Quantum Gates
Pauli X gate(bit flip gate) - Negation
● It acts on a single Qubit
● It is quantum equivalent of the NOT gate
in classical computer
Controlled NOT gate
● Used for Qubit
Entanglement

Hadamard Gate**
● It acts on a single Qubit
● It creates superposition of Qubit after operation.

Qubits representation in Entanglement
It the product of two Qubit state cannot be factored, they are said to be entangled.
How can we reach an Entangled state ? it's easy !!!
Qubits representation in Quantum Entanglement

Tools available in Industry

Qiskit

Blog Promotion

Superposition and Entanglement (Qiskit)

Pauli X gate with Qiskit

Quantum Teleportation Algorithm

Bernstein-Vazirani Algorithm

Faster than light?
Quantum Teleportation
That's called as EPR paradox
If we find the way its communicating the information, it is being transferred faster than light.
Even Albert Einstein called this action as
“Spooky action at a distance”

Building a single Qubit using transistor-
phosphorus atom

Quantum Supremacy
Honeywell, Google,Microsoft,IBM,D wave

Recent achievements
Google says that its 54-qubit Sycamore processor was able to perform a calculation in
200 seconds that would have taken the world’s most powerful supercomputer 10,000
years.
IBM unveils its first commercial Quantum computer the IBM Q System One. Its a 20
Qubit computer.
IBM also has a 53 qubit computer where we can access it through cloud.
Intel confirms development of a 49 qubit called “Tangle Lake”.

Limitations
● An observer can never know the Qubits state, only know the probability of their state.
● Have to maintain the same state. The same calculation done second time it will give
slightly another answer.
● Currently scientist are working on algorithm that amplifies the correct answer(wave
function in Qubit) to maintain same state
● Very very sensitive to noise, vibration, electromagnetic radiation
● Should be in absolute zero(0 K) -273.15 C

Nope: Not a replacement for classical
computer
● It can be used for doing only special type of calculations
● It's not universally faster.
● Improvement is not on the speed of operation if the number of operations are
exponentially higher to arrive at the result we use quantum computer

Further Session Topics
Quantum Error Correction
Quantum Programming Language Design
Quantum Cryptographic Key Exchange

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