Talk by Rana Prathap from IIT Kharagpur on the Introduction to Quantum Computing at the first Quantum Computing meetup in Hyderabad. Venue: T-hub, IIIT Hyderabad

1. It’s Fundamentally differentQuantum computing 101
With Qiskit
Rana Prathap
IIT Kharagpur (Math and Computing),
Qiskit Camp Asia 2019.

2. 2020 Budget speech by FM Nirmala Sitharaman

3. It’s Fundamentally different
● Quantum bit (Qubit):
Source

4. where are we in Quantum Computing?
Google Quantum Supremacy
performed the target computation in 200 seconds, and from
measurements in the experiment we determined that it would
take the world’s fastest supercomputer 10,000 years to produce
a similar output.
2019
First quantum computer you can buy
D Wave (founded in 1999) made the first commercially available
for 10 million dollars.
2011
Richard Feynman
Richard Feynman points out that quantum systems can only be
effectively simulated using a quantum computer. Exponentially
increasing problem complexity.
1985
Shor’s factorization algorithm
A seminal paper by Peter W. Shor proposed an algorithm that
can exponentially speed up factoring a number.
1996

5. What are we learning today?
Quantum Mechanics
Quantum Information
Quantum
Computation
Gate based Annealing , ...
Quantum
Cryptography
Information Theory
Quantum Key
Distribution
Quantum Error
Correction

6. How powerful is a QC? (Google Quantum Supremacy)
Classical vs Quantum : 10,000 years vs 200 seconds!!
And that is using just a 54 qubit computer!
1,576,800,000 times speed up! (~1.5 billion)
<- Google’s Sycamore Chip
used for showing quantum
supremacy

7. Image Source

8. Quantum Use Cases
Airbus Quantum Challenge

9. Properties that make QC’s different
● Superposition
Exponential speedups as number of qubits grow
● Entanglement
Spooky action at a distance.
● Reversible computing
10-15W vs 20kW (Energy consumption of chip vs cryostat)
● Privacy (No-cloning theorem)

10. Quantum Algorithms
● Shor’s factorization algorithm
● Grover’s search algorithm
● Deutsch-Jozsa algorithm
● HHL algorithm - Quantum machine learning
Useful in the NISQ era - (these are mostly hybrid algorithms)
● QAOA - Quantum Approximate Optimization Algorithm
● VQE - Variational Quantum Eigensolver

11. Quantum Programming
● OpenQASM
● pyQuil (Forest SDK)(Rigetti)
● Qiskit (IBM) : IBM Q Experience
● Q# (Microsoft) : Azure Quantum (Honeywell, QCI,
IonQ)
● : Amazon Braket (Rigetti, IonQ, D-Wave)
● Cirq (Google) : Google NISQ applications

12. Problems faced today
● Hard to build and retain
qubits due to decoherence
● High amount of noise
● Need for better quantum
algorithms
● Algorithms like Shor’s can’t
be implemented today
● All hardwares have their own
pros and cons
● Data storage?
● Debugging?

13. Qubit?
Analogous to the coin flip example - a
coin, while its spinning in the air is
in a superposition of heads and tails.
Bloch sphere representation of a qubit
We require a cylinder to accommodate for
the extra degree of freedom - phase
Ignoring global phase

14. Qubit - (math starts here)
Mathematical representation:
Bloch Sphere:
I like to think of it as polarization of light.
X and + basis

15. Bit of math
● Quantum states are column vectors
● Multiple qubit states. How do we get there?
(Kronecker product)

16. Kronecker Product

17. A few gates
Let’s look at a few gates and
build up to a quantum adder!

18. Using kronecker product for parallel gate operations
● Parallel gates (use kronecker product)
● Serially wired gates (use matrix multiplication)

19. Pauli - X gate (similar to classical not)
● Flips |0> to |1> and
vice versa

20. H gate (Hadamard)
● Puts any state in an equal
superposition of basis
states (phase will vary)

21. CX/Cnot (If…then) -- XOR?
● If (control = 1){
Then flip target qubit
}

22. Ccx/toffoli gate
● Similar to a
classical AND
circuit

23. Classical adder to a Quantum adder
● If first qubit is
true then flip
second.
● Double controlled not

24. Resources to explore
● Qiskit tutorials
● Qiskit textbook
● Qiskit Camp projects - some project ideas
● Interactive map of various QC companies
● Q2B conference videos
● Rigetti Computing
● D Wave - quantum annealing
● Quantum computing for computer scientists - book
● Amazon braket
● Google Cirq
● Google quantum supremacy paper
● IBM Quantum Challenge 2019
● Quantum Computing Report

25. Quantum computing in India - IndiQ
Monthly meetups in major cities like Hyderabad, Delhi,
Bangalore.
Meetup group
Twitter
Website’s coming soon at indiq.in
Join the Qiskit slack workspace which has a #india channel

26. Can’t thank them enough
● Frederik Hardervig - Qiskit Advocate, Co-organizer
Core Team:
● Sunayana Patro
● Utkarsh Azad
● Mahathi Vempati
● Nikhil Vemuri

27. Time for some
questions!

28. Image sources
● Bloch sphere gifs: https://desireevl.com/posts/quantum-intro
● Quantum gates: https://en.wikipedia.org/wiki/Quantum_logic_gate
● Kronecker Product: https://en.wikipedia.org/wiki/Kronecker_product
● Sycamore chip: https://www.nytimes.com/2019/10/30/opinion/google-quantum-computer-sycamore.html
● Quantum computer: https://www.roche.com/quantum-computing.htm
● Airbus Quantum Challenge: https://www.airbus.com/innovation/tech-challenges-and-competitions/airbus-
quantum-computing-challenge.html