01_Introduction_to_Quantum

Outline¶

Background and basic concept of quantum computing
Walk through of the “quantum supremacy” paper (Nature 2019) and the new quantum advantage on chemical simulation paper (Science 2020)
Python implementation of quantum computing (Jupyter notebook)
Discussion of quantum computing in single-cell studies, structure prediction, function prediction and other areas of bioinformatics

A very informative review of quantum computing¶

I suggest that everybody reads this paper (in addition to Wikipedia and other general online tutorials)

Basic Concepts¶

In a classical computer, a bit can store either a 0 or a 1. A qubit can store not only 0 or 1 but also an in-between state called a superposition—which can assume lots of different values.
Classical computer: use 0/1 to represent building blocks, and use gates (and,or,not,xor, etc) to represent operations
Quantum computer: use qubit to represent building blocks, and use gates (SWAP, CNOT, etc) to represent operations

Schrödinger's cat¶

Classical computing: a cat is either alive (bit: 1) or dead (bit: 0)
Quantum computing: a cat that may be simultaneously both alive and dead (without observation)
As soon as you observe it, the whole system collapse (it is either alive or dead) https://en.wikipedia.org/wiki/Schr%C3%B6dinger%27s_cat

Entanglement¶

The phenomenon of correlation between multiple qubits, known as quantum entanglement, is a fundamental resource of quantum computation. a qubit can be in any superposition of the states |0> (such as cat is dead) and |1>(such as cat is alive). a and ß are known as the amplitudes

Entanglment¶

When we have 2 qubits, there is entanglement. The composite system can adopt any superposition of the states {|00>, |01>, |10>, |11>} One of the possible superpositions is the Bell states below. Basically the first qubit determines the second one. (there is entanglement because any operation applied to the first qubit affects the outcomes that of the second qubit; if first qubit is 1 then second qubit must be 0 and vice versa)

Quantum Gates¶

In quantum computing, information is stored in qubits, and is manipulated using quantum gates
In classical computing (such as Python programming language), information is stored in variables and manipulated by functions
So in principle, it is possible to simulate many quantum gates using Python functions (mostly matrix operations), which we will build in the Jupyter notebook session

We can test these gates later in Jupyter Notebook session (for example, an H gate and an CNOT gate is used in (d) to generate the output from two input qubit)

Theoretical advantages that may relate to bioinforamtics¶

Ref: https://onlinelibrary.wiley.com/doi/full/10.1002/wcms.1481

Bioinformatics applications¶

quantum computing is already applied in a variety of fields, including machine learning, quantum chemistry, and drug discovery.
There was even a large grant opportunity on using it on brain genomic data as part of the Convergent Neuroscience consortium

What does a quantum computer look like?¶

qubits need to be almost perfectly isolated from heat, vibration, and stray atoms
Image from https://www.technologyreview.com/2020/02/26/916744/quantum-computer-race-ibm-google

Photon-based quantum computer¶

The Google and IBM quantum computers are both built using superconduction (so they require very low temperature and superconducting materials)
The USTA quantum computer (https://science.sciencemag.org/content/early/2020/12/02/science.abe8770) is built by photons as shown to the left

A quantum-computing advantage for chemistry¶

Motivation: real-world applications of successfully simulating a simple chemical reaction relied on the same basic Sycamore design, though it only used 12 qubits.
(1) simulated a simplified version of the energy state of a molecule consisting of 12 hydrogen atoms, with each of the 12 qubits representing one atom’s single electron.
(2) modeled a chemical reaction in a molecule containing hydrogen and nitrogen atoms, including how that molecule’s electronic structure would change when its hydrogen atoms shifted from one side to the other.

Journal Club on Quantum Computing¶