### Google just built a quantum computer(?), and Pakistan is sitting ducks!

Abdullah Khalid

Quantum Information Scientist

Guftugu Seminar Series

11th October 2019

## How to prepare for the coming quantum computing age.

## What is a computer?

Chemistry

Biology

Computer science

Computing Machine = Physical System

### Computers solve computational problems

Decision

Search

Optimization

## Decision Problems

### Multiplication

Input: integers P and Q

Output: integer R = P x Q

### Factorization

Input: integer R

Ouput: prime numbers P and Q

such that R = P x Q

R = 21

digits = 2

R = 498556150811

digits = 12 = problem size

General number field sieve algorithm

## Computational Complexity

Multiplication

Factorization

Resources = time/memory

Problem size (n)

Hard/inefficient

Easy/efficient

### Application of computation: Cryptography

"Top secret info"

"Top secret info"

"hf72h18v82ja9"

You

You

Military

Bank

Email provider

Military

# RSA encryption protocol

Encryption/Decryption = Multiplication = Easy

Cracking = Factorization = Hard

Rivest–Shamir–Adleman

Key: 10101011101...

Security ∝ number of digits

Recommended key size: 4096 bits

(for security till 2030)

## Cracking RSA

## Sampling Problems

### Binomial sampling

Input: n, p

Output: a sample from the binomial probability distribution

A random number generator!

"The underlying **physical laws ... of physics and the whole of chemistry** are thus completely known, and the difficulty is only that the exact application of these laws leads to equations much **too complicated to be soluble**." 1929

# Simulation Problem

Simulating atoms, molecules and materials

Paul Dirac

# Quantum Computers

Computing Machines = Physical Systems

=> Computational complexity is determined by physical laws

# Visions of Quantum Computing

Simulating atoms, molecules and materials

Simulate this

By controlled experiments on this

## Quantum Computers: The transport analogy

Laptop

Super computer

Quantitative

Qualitative

Quantum computer

Solve computational problem = Go from A to B

### Quantum computers can

## simulate atoms, molecules and materials,

### exponentially faster than classical computers.

### Quantum computers can

## maybe do machine learning and optimization

### exponentially faster than classical computers.

### Quantum computers can

## break all currently used asymmetric encryption protocols

### exponentially faster than classical computers.

arXiv:1909.07353

## Cryptographic Algorithms in Use

### Quantum computers CANNOT

~~do industrial optimization~~

predict the stock market

optimize airline schedules

predict the stock market

optimize airline schedules

~~NP-Complete problems~~

### exponentially faster than classical computers.

If this was true, quantum computers could solve NP-complete problems efficiently

But they don't!

## Quantum vs Classical Computers

Breaking encryption on Quantum Computer

Text

NP-Complete Problems on Classical/Quantum Computer

Breaking encryption on Classical Computer

Resources

Problem size (n)

# Quantum Computing Today

### Road to Quantum Computers

Quantum computers

Quantum supremacy devices

Solve a (useless) problem exponentially faster than a classical computer

Solve a (useful) problem exponentially faster than a classical computer

Analogy

Nature | Vol 574 | 24 OCTOBER 2019

## Quantum Random Circuit

**Computational problem**

Input: Circuit C

Output: a sample from the output probability distribution of C

Difficult for classical computer

Outputs = 2^{n} Output strings, each with different probability

## Google's superconducting chip

53+1 qubits, depth = 20

# How to verify a device which you claim can't even be classically simulated?

## Is quantum supreme?

Google's claim: 10,000 years on a state of the art supercomputer, using the best classical algorithm they could think of.

IBM's claim: Sorry, 2.5 days only, using our better classical algorithm!

Quantum device performance: 600 seconds to sample 3 million times

# How do we prepare for the coming quantum computing world?

## First Option: Post-Quantum Crypto Algorithms

arXiv:1909.07353

No proofs of security, but hope!

## Second Option: Quantum Key Distribution

Secret key: 1011101111010... for symmetric key encryption

## Second Option: Quantum Key Distribution

$5000-50,000

### To prepare for the quantum computing age, Pakistan should...

## Invest in quantum computing and cryptography research.

### To prepare for the quantum computing age, Pakistan should...

## Build quantum cryptography infrastructure.

### To prepare for the quantum computing age, Pakistan should...

## Invest in quantum computing and cryptography research

### To prepare for the quantum computing age, Pakistan should...

## Participate in international encryption standards committees.

#### Google just built a quantum computer(?), and Pakistan is sitting ducks! How to prepare for the coming quantum computing age.

By abdullahkhalids

# Google just built a quantum computer(?), and Pakistan is sitting ducks! How to prepare for the coming quantum computing age.

- 739