Getting Started with quantum computing-part I.

Getting started with quantum computing-part I.

This document translates D-ware Company's "Quantum Computing Primer", in which there is insufficient or wrong to welcome everyone to point out. Original source: https://www.dwavesys.com/tutorials/background-reading-series/quantum-computing-primer#h1-0

This tutorial is intended to introduce the concepts and terminology used in quantum computing, provide an overview of quantum computers, and why you want to do quantum computing programming.

Content

Getting Started with quantum computing-Part one part 1-Traditional Computing 2-a new way to calculate 3-light switch Game 4-How quantum mechanics works

This material is written using very advanced concepts that can be used by both technical and non-technical readers. Having some physics, math, and programming backgrounds is not necessary, but it helps to understand the concept of the document,

What you can learn

By reading the material in this tutorial, you will learn how quantum mechanics gives us a new way to calculate the similarities between quantum computing and classical computing and how the basic units of quantum computing (qubits) are used to solve difficult problems why quantum computing is well suited to AI and machine learning applications, And how quantum computers are used as "AI coprocessor" part 1.1-Traditional computing

This is useful for understanding quantum computing, considering the traditional calculations first. We are accustomed to modern digital computers and their ability to execute many different applications. Our desktops, laptops and smartphones can run spreadsheets, live videos, and let us chat with people on the other side of the world, and immerse us in a very real 3D environment. But the core of all digital computers has something in common. They all perform simple arithmetic operations. Their ability to do this comes from their very fast speed. The computer performs billions of operations per second. These operations are executed very quickly and they allow us to run very complex advanced applications. Traditional numerical calculations can be summarized in the chart shown in Figure 1.

Figure 1. Data flow in a traditional computer

Although traditional computers are good at many tasks, computing in some areas is still very difficult. Examples of these areas are image recognition, natural languages (in their own language, not programming languages, making computers understand what we mean), and better specific tasks that computers must learn from experience. Although there has been a lot of research and effort in this field over the past few decades, we are still progressing slowly in this area, and our prototypes often require very large supercomputers to run, consuming a lot of space and energy.

We can ask the question: Is there a fundamentally different way to design a computer system in the world? If we could start from scratch and do something completely different, it would be better to accomplish a task that is difficult for a traditional computer. So how are we going to start building a new kind of computer? 1.2-A new way of computing

The traditional method transforms the bit strings of 0 and 1 into the other, and the methods of quantum computation are very different. In quantum computing, everything is changing. We understand that the physical layers of information bits and the devices that manipulate them are completely different. The way we make this kind of equipment is different, requiring new materials, new design rules, and new processor architectures. Finally, the way we program these systems is completely different. This document explores the source of these issues, namely how to replace the traditional bits (0 or 1) with a new kind of information-the qubits-that can change the way we think about computing. 1.3-light switch game

It is also important to understand why we can use traditional computers to solve certain problems before studying quantum computing. Let's consider a mathematical problem called a light switch game, which can be a good illustration of the key.

The light switch game involves trying to find the best settings in a bunch of switches. Here is an example of a diagram that illustrates this problem:

Figure 2. Light Switch Game

Let's imagine that each light switch has a number that is closely related to it and is given to you (you don't have to change this). We call this number "deviation value". What you have to do is: switch on or off for each lamp to select. In our game, open represents 1, turn off the representation-1. We then multiply the deviation values of all the switches by the corresponding Open/closed values. This will produce a result. The intention of this game is to set all the switches to open the off state to get the minimum value. Mathematically, we define the deviation value of each switch as Hi h_i, and the switch setting is called Si s_i.

Figure 3. Play the light switch game, multiply each switch's deviation value by their setpoint (you have to choose) and add total.

So, depending on which switch we set is + 1 (open), which switch is 1 (off), we will get a different score. You can try this game. Hopefully you'll find it easy, because there's a simple rule of thumb:

Figure 4. A special "conjecture" for this switch is answered

We found that if we set all the switches with positive deviations to be off, the switch with negative deviations turned on, and then total, we would get a minimum value. It's easy. I can give you as many switches as possible with different deviations, and you just have to look at the switches and turn them on and off.

OK, let's make the problem more difficult. Imagine that there is a number of "pair" switches with an additional rule, which is considered to involve a "pair" switch instead of a switch. We add a new deviation value (called J j), we multiply it with the set value of the two connected switches, and for all switches, we add the result value of each pair of switches. Still the same, what we need to do is to choose the switch state to turn on or off to accommodate this new rule.

Figure 5. Increased game complexity by adding additional items that depend on set values for paired switches

But now this is very, very difficult to decide which switch should be turned on or off, because its proximity to the switch will affect it. Even if it is simplified to the case of only two switches in the previous figure, you still cannot use the previous rule, which is to set them to the opposite value of the deviation value symbol according to the deviation value (you try). In the face of all the switches having a neighbor's complex network, it's hard to find the right combination to get the minimum value.

Figure 6. Electric light switch game with additional rules to produce a reciprocal effect of the light switch network

1.4-How quantum mechanics works

Each pair of switches if you try all combinations, there are four possibilities: [Open, open],[Open, close],[off, open],[off, off]. But as you increase the number of switches, the number of possibilities will increase exponentially with the number of switches:

Figure 7. Light switch game brings exponential problems

You should start to understand why this game is not so fun. In fact, this problem is even difficult for most powerful supercomputers. It will take a very long time to put so many possible configurations into memory and send them to the traditional processor to calculate whether our guesses are correct. Assuming 500 switches, there is not enough time in the universe to check all the configurations.

Quantum mechanics can help us in this matter. The basic power of quantum computers comes from the idea that you can put a quantum bit of information into a superposition state, and you can imagine a situation in which qubits have not decided what they want to call the state. Some people like to think of this superposition state as "having two states at the same time." Or you can think of the state of the qubit as not deciding whether to choose +1 or-1. This means that if a quantum computer is used, our light switches can be turned on and off at the same time.

Figure 8. The information bit (q bit) of the quantum mechanism can exist in a known superposition state, and the superposition state is not chosen to be +1 or 1 (in other words, you can think of it as +1 and 1)

Now take a look at the same number of switch groups as before, but now feed into the memory of the quantum computer (note that the deviation value has not been added).

Figure 9. A network of quantum bit superposition states where the answer is somewhere.

Because all the light switches are on and off at the same time, we know the correct answer (open/close each switch correctly) somewhere, it's just hiding from us right now. But it's no problem, because the quantum mechanics will find it for us. D-wave Quantum computers allow you to use one of these "quantum representations" and then extract the open and closed configurations to get the minimum value. Here's how it works:

Figure 10. The computer uses the superposition state bit to start the calculation, and at the end produces the traditional normal bit stream, according to this method to find the answer

You start the system described above in the quantum superposition state, and then you slowly adjust the quantum computer to turn off the quantum superposition effect. At the same time, you slowly adjust all the deviations (H H and J J to be first). When this operation is performed, all switches will slowly jump out of their superposition state, choosing a traditional state, i.e. open or close. Finally, each switch must select a state, open or close. When you finally add them up, the quantum mechanism used inside the computer helps the switch set to the correct state to get the minimum value. Although n-n switches may produce a 2N 2^n probability configuration, it can also find the minimum value at the end to win the light switch game. So, we can know that quantum computers allow us to streamline expressions as follows:
[E (s) =∑IHISI+JIJSISJ] \ [E (s) = \sum_i h_i s_i + j_{ij}s_i s_j \]
This is very difficult for traditional computers (or impossible to complete)

Part II: Introduction to Quantum computing-Part Two