Author: Zen and the Art of Computer Programming
1 Introduction
With the rapid development of information technology, more and more enterprises have begun to choose terminal equipment as the main battlefield for global digital transformation, and it has become possible to deploy and run quantum computing platforms on terminal equipment. In recent years, as the advantages of quantum computers such as high performance, high fault tolerance, and low cost have gradually attracted attention, end users have also paid more and more attention to the application scenarios of quantum computing. This article proposes five major challenges for quantum computing terminal applications based on the development of quantum computing in the field of terminal applications and its main technical problems. Through technical research on quantum computing terminals, the author systematically elaborates on the technical principles and application directions of quantum computing terminals. At the same time, it also pointed out the technical bottlenecks of quantum computing terminals and their solutions. Finally, the author looks forward to the future application prospects of quantum computing terminals.
2. Background Introduction Quantum Computing is a computing model constructed using one of the laws of physics - quantum mechanics. It can accurately simulate many phenomena in the real world, such as astrophysics, materials, chemical reactions, machine learning, etc. In recent years, as the advantages of quantum computers such as high performance, high fault tolerance, and low cost have gradually attracted attention, end users have also paid more and more attention to the application scenarios of quantum computing. According to a survey, it is estimated that more than three trillion pieces of data are generated globally every year, of which more than 87% comes from mobile devices, computers, embedded devices, etc. This makes terminal devices with increasingly powerful computing capabilities an important player in the future digital economy. But at the same time, due to the unique characteristics of terminal equipment, the technical difficulties faced by quantum computing in this field are becoming increasingly complex. The following will briefly introduce the history, development, technical problems and currently ongoing work of quantum computing in the field of end applications.
2.1 History The invention of quantum computers can be traced back to 1982. At that time, Werner Perelli, a professor of physics at the University of Edinburgh, proposed the law of quantum gravity. He found that it was very different from the classic Maxwell equations, and this discovery was widely recognized and approved by the US Department of Defense. To prove this, Perelli invented a computer. This is the first quantum computer, and the first to operate successfully.
2.2 Development Due to the potential value of quantum computers, an astonishing number of quantum computing projects have emerged in recent decades. For example, IBM Q System One (Global Quantum Computing Center) plans to complete the first level of experimental testing of quantum computers by the end of August this year. Mark Zein, founder of ProjectQ, an open source quantum computing software package in the field of artificial intelligence and machine learning, said: "Quantum computing has become a sign of the second industrial revolution." Another field of quantum computing, namely in quantum communications, quantum information and Breakthrough progress in fields such as quantum Cryptography. These breakthrough developments have enabled quantum computing technology to gain more attention in the terminal field.
2.3 Technical difficulties The technical difficulties faced by deploying quantum computing platforms on terminal devices mainly include the following aspects.
First, how to deal with the storage of quantum states? Since the size of quantum states often cannot be stored directly, certain methods need to be used to save and read quantum states. Currently, commonly used methods include quantum entanglement, circuit quantum logic, and hybrid quantum circuits. These methods are all effective, but there is still a lot of overhead. In addition, since the information entropy of quantum states is often low, it is also necessary to consider how to compress the quantum state to reduce the amount of transmission.
Secondly, there are resource limitations of quantum computing platforms. At present, the computing capabilities of terminal devices are generally limited and cannot provide a large number of quantum operations. Therefore, how to improve computing capabilities has become a key issue for end users. This requires the terminal device to automatically schedule quantum tasks to make full use of hardware resources.
Third, the security of quantum computing platforms. Currently, quantum computing platforms face strict security guarantees and laws and regulations. Especially in some sensitive application fields, such as quantum finance, quantum technology, quantum biology, etc., security protection is particularly important. However, how to establish a security foundation for quantum computing platforms, maintain security levels, and implement timely update measures is still a key issue.
Fourth, privacy protection of quantum computing platforms. Although modern quantum computing technology can achieve arbitrary calculations, for some specific application scenarios, it may bring privacy risks. For example, the infringement of patient privacy by medical imaging data may cause significant harm. How to protect personal privacy, including data security, computing process security, and control authority distribution, are also technical problems faced by quantum computing in the terminal field.
Fifth, the migration and maintenance of quantum computing platforms. With the continuous growth of various types of terminal devices, end users hope that their quantum computing platforms can be migrated across platforms and systems. Traditional methods generally only support a single platform or system. Therefore, how to design an effective migration solution to reduce the burden on developers is also one of the problems that quantum computing terminals need to solve.
To sum up, the technical problems faced by quantum computing in terminal applications mainly include three aspects: resource limitations, security, and privacy protection. The key to solving these technical problems is to optimize resource utilization, increase developer convenience, and improve security mechanisms.
3. Basic concepts and terminology of quantum computing 3.1 Quantum State Quantum state is a specific set of wave functions of a quantum system that describes the state of the material world. Its essence is the superposition of quantum particles in space and time, which is called the wave function. Any given quantum state consists of two vectors: the quantum ensemble in one dimension and the quantum tensor integral in two dimensions. Here, we simply define quantum states as one of two forms - nuclide-based or qubit-based.
Quantum state representation based on nuclide:
If a quantum system is regarded as a strange microscopic world, then a nuclide-based quantum state is an atom in the microscopic world. The nuclide here is a fictitious particle similar to an electron. Like all other atoms, it has its own position and movement, and can move according to the laws of quantum states. Each nuclide has a quantum number that describes its probability of excitation.
Quantum state representation based on qubits:
Another way of representing quantum states is based on qubits. In this representation, each qubit represents a special state, and its superposition state represents the overall properties of the entire system. Qubits can be represented by binary encoding. Specifically, each qubit is represented by two basis vectors: |0> and |1>. If a qubit is in the |0> state, then it is only subject to quantum effects from the other qubit. In contrast, if a qubit is in the |1> state, it will be affected by all types of quantum gates.
3.2 Quantum Gate Quantum gate is a basic operation used to convert quantum states. In practical applications, quantum gates are usually divided into two categories - transformation gates and control gates. The transformation gate applies practical operations to a quantum state, while the control gate is used to control the effect of the quantum gate on a specific qubit.
Transformation gate:
Commonly used transformation gates include: Hadamard gate, Pauli-X gate, Pauli-Y gate, Pauli-Z gate, S gate, T gate, CNOT gate, etc. Their role is to impose the effects of specific operators on a quantum state. For example, a Hadamard gate acting on a quantum state will transform the state into a new state, which divides the two basis vectors of a qubit into two parts. In addition, there are also Pauli-X, Y, and Z gates, which only apply different operators, but no matter what, they will change the quantum state.
Control door:
The role of the control gate is to impose a quantum gate on a specific qubit. Specifically, a control gate can switch between zero and one states, or impose a gate on a subset of a state. Control gates include CNOT, SWAP, Toffoli gates, etc.
3.3 Quantum Bit Quantum bit is the smallest unit of quantum computing and a basic information processing element. It consists of two levels of atoms and ions, as shown in Figure 3-1.
Figure 3-1 Basic structure of qubit
As you can see from the figure above, each qubit consists of two basis vectors, which represent two different quantum states. The difference between them lies in their energy difference. They can be excited by external physical media or disturbed by quantum physics. Due to the existence of qubits, the computing efficiency of quantum computers has reached unprecedented heights.
3.4 Evolution of Quantum States The evolution of quantum states actually refers to the change process of a quantum system from an initial state to a final state. Through the evolutionary process, we can perform various measurements on quantum systems to obtain information. In quantum computing, the evolution of quantum states usually appears in the form of matrices, and matrix multiplication is the basic evolution rule of physical systems. Specifically, assume that a quantum state can be written as follows:
$$|\psi\rangle = \sum_{i=0}^{n-1} c_i |i\rangle$$ （1）
Here, $|i\rangle$ is a hypervector composed of basis vectors of $n$ qubits, and $c_i$ is $n$ non-negative real numbers, and their sum is 1. So, how to find another quantum state that is the same as the initial state? By applying the initial state to a certain matrix transformation, the initial state can be transformed into another quantum state. For example, in Figure 3-2, you can see that the ground states of the two qubits are $|0\rangle$. Through the action of a CNOT gate, the ground states of the two qubits can be switched to $|0, 1\rangle$.
Figure 3-2 Evolution of CNOT gate
Readers who do not know about matrix multiplication can refer to linear algebra related knowledge. Assuming there are two matrices $A$ and $B$, their product can be written as:
$$AB=\begin{pmatrix} a_{11} & a_{12} \ a_{21} & a_{22}\end{pmatrix}\begin{pmatrix} b_{11} & b_{12} \ b_{21} & b_{22}\end{pmatrix}= \begin{pmatrix} a_{11}b_{11}+a_{12}b_{21} & a_{11}b_{12}+a_{12}b_{22} \ a_{21}b_{11}+a_{22}b_{21} & a_{21}b_{12}+a_{22}b_{22}\end{pmatrix}$$ （2）
Here, $a_{ij}$ and $b_{kl}$ are elements of the $2\times2$ matrix, and $\alpha,\beta,\gamma,\delta$ are real numbers. Assume $A=(\alpha I+\beta X)$,$B=(\gamma Y+\delta Z)$, then:
$$A B=\alpha(\gamma I-\delta Z)+\beta(\delta I+\gamma Z)=\begin{pmatrix} \alpha\gamma & -\alpha\delta \ \beta\gamma & \beta\delta\end{pmatrix}$$ （3）
Therefore, by applying the initial state to a certain matrix transformation, the initial state can be transformed into another quantum state. And this is the core idea of quantum computing.
3.5 Quantum Algorithm Quantum algorithm refers to a method that uses quantum computing to solve certain problems. It usually involves preparing a quantum state and then evolving the quantum state to find a set of mathematical relationships. Many quantum algorithms are considered a black box, and users cannot directly understand their inner workings and can only interact through input and output.
4. Technical principles and application directions of quantum computing terminal applications 4.1 Task decomposition and automatic scheduling At present, the application scope of quantum computing has expanded to various business fields, including finance, biology, machine learning, remote sensing, logistics, etc. Therefore, how to split a complex task into several simple subtasks and how to automatically schedule these subtasks has become a technical problem for current quantum computing terminals.
A key way to solve this problem is to decompose atomic tasks into multiple small tasks that are executed in parallel, and then allow these small tasks to be automatically scheduled on the quantum computing platform. By decomposing tasks, the computational complexity of the task can be reduced and its execution efficiency improved. In addition, you can also prioritize tasks by using the resource manager, so that high-priority tasks can be executed quickly, while low-priority tasks can be queued for execution.
In addition to decomposing tasks, other methods can be used to reduce dependencies between tasks and increase task parallelism. For example, a distributed computing framework can be used to execute the same quantum algorithm in parallel on different processing units. In addition, asynchronous programming models can also be used to reduce data communication overhead and improve quantum computing performance.
In short, automatic scheduling can greatly improve the throughput and utilization of quantum computing platforms, while also reducing the burden on developers.
4.2 Quantum Accelerated Computing Currently, most quantum computing platforms are quantum computing based on hardware (such as quantum gates, quantum chips, etc.). However, with the continuous development of quantum algorithms, more and more applications are beginning to call the functions of quantum computing platforms, such as graphics processing, quantum chemistry, quantum machine learning, quantum communications, etc. Therefore, how to improve the computing power and computing density of the platform by transforming hardware and software has become a technical problem for current quantum computing terminals.
One approach is to use tree-structured quantum chips. This kind of chip can stack quantum gates, logic gates, noise gates, etc. layer by layer to form a neural network, thus improving quantum computing capabilities. In addition, integrated circuits can be used instead of vacuum tubes to reduce the size of the hardware.
Another approach is to use a compiler to improve computational efficiency. Currently, commonly used compilers include Qiskit, Cirq, ProjectQ and Pyquil. They can both convert classical programs into sequences of instructions that can be run on a quantum computer. Therefore, by converting classical programs into quantum programs, quantum computing efficiency can be improved to a certain extent.
In short, breakthrough progress in quantum computing terminals is mainly reflected in improving computing capabilities.
4.3 Programmable Quantum Array With the promotion of quantum computing, many quantum algorithms have great potential, such as quantum cryptography, quantum randomness, quantum circuits and quantum machine learning. Therefore, how to build a programmable quantum computing platform has become a technical problem for end users.
One approach is based on cloud computing platforms. The cloud computing platform can provide a complete quantum computing environment. Developers can write algorithms into codes that can run on the cloud platform, and then submit them to the server for execution through the cloud platform. The advantage of this is that developers do not need to purchase their own hardware equipment, reducing purchase costs, and at the same time can enjoy the high-performance computing capabilities provided by the cloud platform. In addition, the cloud platform can also automatically allocate computing resources to meet the computing needs of different quantum tasks.
Another approach is to use quantum computing chips directly. Currently, quantum computing chip manufacturers are exploring quantum computing platforms based on programmable gate arrays, which can directly control the behavior of qubits through software programming interfaces. This method helps reduce programming difficulty for developers and improve application efficiency.
In short, quantum computing terminal applications based on programmable gate arrays have gradually become a hot spot in the field of quantum computing.
4.4 Quantum Security Quantum security has always been a difficult problem in the field of quantum computing. Over the past few decades, governments around the world have used various means to attempt to attack and disrupt quantum computing technology. But although countries and companies have begun to treat quantum security issues cautiously in recent years, its impact is still huge.
Recently, international organizations such as the U.S. Department of Defense, the British Government, and the Ministry of Foreign Affairs of the Russian Federation jointly released a report. The report pointed out that due to the breakthrough and growth of quantum computing technology, it is likely to cause regime changes, make political connections between countries closer, and even threatens the global order. In order to avoid this danger, technology leaders and the industry should take joint actions, seize opportunities, strengthen response awareness, establish an international cooperation framework, and jointly respond to the challenges of quantum computing technology.
Quantum security has always been a challenging field and only in the future will further developments be seen. The application of quantum computing terminals has become an important field in the technical field. How to improve the security level of quantum computing terminals will also become an urgent problem in the technical field.
4.5 Future Quantum Computing Terminal Applications The future of quantum computing terminal applications will not be limited to the field of quantum computing. Currently, with the development of the Internet of Things, 5G and artificial intelligence, intelligent manufacturing is becoming more and more prosperous. Intelligent manufacturing is developing at an alarming rate, which will gradually bring quantum computing technology into every aspect of the manufacturing industry. How to use quantum computing technology in the field of intelligent manufacturing and open up all links in the intelligent manufacturing system will become an irreplaceable key technology for quantum computing terminal applications.