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arXiv:2409.15285

Quantum states and quantum computing

M. V. Takook, Ali Mohammad-djafari A

Published Sep 3, 2024• 1 citation
arXivHTMLPDF

Abstract

In classical theory, the physical systems are elucidated through the concepts of particles and waves, which aim to describe the reality of the physical system with certainty. In this framework, particles are mathematically represented by position vectors as functions of time, $\vec{x}(t)$, while waves are modeled by tensor fields in space-time, $Φ(t, \vec{x})$. These functions are embedded in, and evolve within space-time. All information about the physical system are coded in these mathematical functions, upon which the classical technologies are developed. In contrast, quantum theory models the physical system using a quantum state $\vert α,t\rangle$, situated in an evolving within Hilbert space, portraying the system's reality with inherent uncertainty. Despite the probabilistic nature of reality observation, the quantum state $\vert α,t\rangle$ can be precisely determined due to the unitary principle, provided we know the initial state. Therefore, it can serve as a foundation for developing quantum technologies, which we call quantum state-tronics similar to electronics. This discussion focuses on quantum computation, given its expansive scope. One of the paramount challenges in quantum computing is the scarcity of individuals equipped with the requisite knowledge of quantum field theory and the training necessary for this field. This article aims to elucidate the fundamental concepts of quantum field theory and their interconnections with quantum computing, striving to simplify them for those engaged in quantum computing.

DOI
10.48550/arxiv.2409.15285

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L., Quantum Computation and Quantum Information. Cambridge University Press, 2000. Duwell, A. Quantum information does not exist. Studies in History and Philosophy of Modern Physics，2003, (34). Berta, M. Christandl, M. Colbeck, R., et al. The uncertainty principle in the presence of quantum memory. Nat. Phys., 2010, (6). Caves， M. and Fuchs，C. A. 1996. Quantum information：how much information in a state vector?. preprint quant-ph/9601025. Barrow, J., et al, Science and Ultimate Reality: Quantum Theory, Cosmology and Complexity. Cambridge University Press. 2004. Yongde Zhang, Principles of Quantum Information Physics. Beijing: Science Press. 2006. Wheeler, J. A., At Home in the Universe. New York: Springer-Verlag. 1996. Guolin Wu, Quantum Entanglement And Its Philosophical Meaning, Studies in Dialectics of Nature, 2005, (7). Guolin Wu, A Detailed Philosophical Inquiry of the Quantum Information, Philosophical Researches. 2014, (8). 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IEEE International Symposium on Circuits and Systems proceedings•Jan 1, 2000•7 citations
In classical theory, the physical systems are elucidated through the concepts of particles and waves, which aim to describe the reality of the physical system with certainty. In this framework, particles are mathematically represented by position vectors as functions of time, x⃗(t)\vec{x}(t)x(t), while waves are modeled by tensor fields in space-time, Φ(t,x⃗)Φ(t, \vec{x})Φ(t,x). These functions are embedded in, and evolve within space-time. All information about the physical system are coded in these mathematical functions, upon which the classical technologies are developed. In contrast, quantum theory models the physical system using a quantum state ∣α,t⟩\vert α,t\rangle∣α,t⟩, situated in an evolving within Hilbert space, portraying the system's reality with inherent uncertainty. Despite the probabilistic nature of reality observation, the quantum state ∣α,t⟩\vert α,t\rangle∣α,t⟩ can be precisely determined due to the unitary principle, provided we know the initial state. Therefore, it can serve as a foundation for developing quantum technologies, which we call quantum state-tronics similar to electronics. This discussion focuses on quantum computation, given its expansive scope. One of the paramount challenges in quantum computing is the scarcity of individuals equipped with the requisite knowledge of quantum field theory and the training necessary for this field. This article aims to elucidate the fundamental concepts of quantum field theory and their interconnections with quantum computing, striving to simplify them for those engaged in quantum computing.
Quantum mechanics has proven its position as the primary theory for accurately describing microscopic domains. Numerous fields in physics utilize quantum mechanics to great effects, with one prominent application being quantum computing. Quantum computing extends the field of quantum mechanics to information theory, striving to perform computational tasks utilizing quantum phenomena with notably greater efficiency compared to classical alternatives. In this thesis, I will go through the basics required in the field of quantum computing. To understand quantum computing demands adapting a new type of matrix mechanical view. This involves considering Hilbert spaces, which are linear vector space having a well defined inner product. Hilbert spaces contain state vectors describing quantum states, as well as operators for altering and measuring these states. The dynamics of quantum systems are governed by three quantum postulates. These specify Hilbert spaces and state vectors as the fundamental components of quantum systems, Hermitian operators as providing the physical manifestation of these systems, and finally, the Schrödinger's equation to describe the time evolution of such systems. These notions are required in producing quantum computing. Quantum computing uses qubits as the computational basis, analogous to classical bits but with the added capability of quantum superposition. Qubits are represented as two-state vectors, and can be physically realized with any quantum-behaving binary-valued system, like the electron spins. Qubits can be combined into higher dimensional states with the use of tensor products, causing the system's Hilbert space to expand as 2^n with n being the number of qubits, allowing for exponential computational speedup. Computational logic can be constructed by acting on the qubits using unitary operators, known as quantum gates. The combinations of qubits and quantum gates can be visualized as quantum circuits, depicted using specialized circuit diagram notations. An essential part of quantum computing, and the phenomena enabling exponential computational speedup, is quantum entanglement. Entanglement arises in interacting qubits, intertwining them so that the individual states become correlated. Entanglement can be characterized by being unable to reduce a combined state into its pure constituents. The amount of entanglement in a system can be measured using von Neumann entropy, analogous to Shannon entropy in classical information theory. Entanglement serves various purposes in quantum computing and is a defining feature distinguishing it from the classical domain. In this thesis, the entanglement properties of a periodic four-qubit circuit with alternating quantum gates were simulated. The simulation was performed computationally, and measured entanglement entropy as a function of the amount of circuit periods. The results demonstrated different characteristics of entanglement depending on the parameters used for the quantum gates, with the entanglement either being periodic, non-occurring or chaotic in nature.
Time and reality are central concepts in both philosophy and physics. While classical mechanics describes the universe as deterministic, where the present emerges from past conditions, quantum theory introduces probabilistic interpretations suggesting inherent uncertainty at microscopic scales. These two perspectives have led to an ongoing debate regarding whether reality is fundamentally deterministic, probabilistic, or a combination of both. The Zia Theory of Temporal Reality (ZTTR) integrates these frameworks by proposing that the present state of reality is determined by accumulated past causes, while the future evolves probabilistically under uncertainty. To formalize this concept, the Zia Unified Continuity Equation (ZUCE) is expressed as a stochastic model where the state of reality represents a combination of initial conditions, integrated causal influences, and stochastic fluctuations represented by a Wiener process. To enhance generality and address limitations of fixed functional assumptions, the uncertainty term is further extended as a generalized function, allowing different forms such as diffusion-like, logarithmic, or nonlinear growth depending on system dynamics. In this framework, deterministic causal accumulation represents the structured continuity of past influences, while the stochastic component reflects uncertainty arising from complexity, interaction, and incomplete knowledge of system variables. This interpretation aligns with developments in statistical mechanics, information theory, and complex systems research. The applicability of the model is illustrated through conceptual and numerical examples drawn from physical processes, biological systems, and learning dynamics. These examples demonstrate that deterministic historical structures and stochastic variations can coexist within a single temporal framework. The Zia Theory of Temporal Reality thus provides a generalized and mathematically consistent perspective on temporal evolution and contributes to interdisciplinary research in physics, complexity science, and artificial intelligence.
Quantum theory and quantum computing in recent years, has raised more and more increasing interest within the scientific community because of various reasons. First, the highly interdisciplinary nature of the subject which involves diverse topics such as, on the theoretical side, information theory and foundational issues of quantum mechanics and on the experimental side, the physics of quantum, optical, atomic and solid state systems. Secondly, the field is extremely promising for revolutionary technological implications in the near future. It is now perfectly clear that one can use quantum mechanics to process and transmit information in a way which does not have a classical analogue, and that using quantum techniques one can implement fully secure cryptographic systems. Recent breakthroughs, such as quantum teleportation, have led to extremely rapid progresses in a fascinating new field and, as a consequence, have attracted the interest of many scientists from varied disciplines. The purpose of this article is to provide a comprehensive overview about the deep involvement of quantum theory in quantum computation to young researchers and newcomers in the field.
A classical simulation of quantum systems demands enormous computational resources. The dimension of underlying Hilbert space scales exponentially with the number of participating elements ( N ), requiring a 2 2N size of calculation matrix for a unitary operation, for example, 2 100 ≈ 10 30 for only N = 50. With the increase of N , the first obstacle to encounter is in fact the deficiency of computer memories. A straightforward resolution is to use a quantum computer, a calculating device that operates with the principle of quantum mechanics. During the last twenty years, quantum computing once considered as theoretical exercise has become an important field of research in modern physics. At the forefront of quantum information technology, quantum computing has emerged as a new engineering field with broad interest not only in physics but also in computer science, electronics engineering, and mathematics.
Introduction The quantum information theory began to rise in the end of 20th century. The EPR (relation)really is quantum entanglement, Consequently, it makes the concept of information in science expand from classical information theory to quantum information theory, and a new concept of quantum information formed. The primary concept of information faced to new challenges and produced some important philosophical questions. For example, can we set up the concept of quantum information? What is the nature of quantum information? The past common concept of information (the information is the elimination of uncertainty) could be used in quantum information? Whether does the emergence of quantum computation mean to eliminate no-boundaries between the quantum and the classical? My aim in this paper is to discuss these questions. My philosophical analysis focuses, however, on the basic quantum information theory. Methods The research method is analytical philosophy and logic that make quantum conception more clear and accurate. Results and Discussion The concept of information could be set up. fundamentally speaking, it did be supported by the Shannon information theory and further philosophical reflections. According of information theory, (classical) information concept could be set up, and there are two necessary preconditions: (a) the premise is a set of possible events, and they can be described by the probability. (b) the information is the elimination of uncertainty. Fundamentally, quantum information is also satisfied with the family-resemblance two preconditions: (1) Quantum information describes the possibility of microscopic things, and quantum information is the expression of wave function. The wave function describes the state of microscopic particles, and presentation of the possibility of microscopic objects. (2) On the aspect of eliminating the uncertainty, the quantum communication is same as classical communication. The signal receiver once received quantum signals transmitted, and the receiver eliminates the corresponding uncertainty of quantum. Therefore, the quantum information is the elimination of quantum uncertainty, and which is called quantum information I. From two point of views, the possible events and eliminate uncertainty, the quantum information and classical information have family resemblance. Quantum information like Classical information way of transmission, it is delivered by the information source, and is received by recipient through the information channel. Quantum Information is similar to classical information, but more essential difference between them, specifically in the following three aspects: (1) The probability directly describe the possibility of classic events, while wave function (or probability amplitude) describes quantum events in the quantum world, and the absolute square of wave function is corresponded to classical probability. (2)There have the essential difference between qubits (quantum qits) and classical bits. (3) Classical information can be completely cloned or deleted. nevertheless, quantum information is neither cloned (no-cloning), nor removed completely. To my point of view, through the analysis of the process of quantum teleportation, a quantum uncertainty can be divided into three categories: the first is the external uncertainties of microscopic particles; the second the uncertainty of the superposition state; the third the inherent uncertainty of microscopic particles. These three uncertainties can be eliminated by three different ways that are transmission of quantum information, accurate quantum transformations and the creations of quantum entanglement. Therefore we can give the general definition of certainty: a situation (the state of events, things) is of certainty, if they are satisfied with the following conditions: (a) a situation is entirely determined by n events parameters; (b) n parameters of events has an accurate values simultaneously. The existences of quantum states form quantum facts. Quantum states show themselves, and therefore it releases the information to the outside world. For this reason, there have two aspects of quantum state which need to express: existence of quantum state is the quantum fact, here we emphasize "existence"; and quantum state can show to the external world, which is the quantum information, here we emphasize "Show". Hence, quantum information is the show(Zeigt) of quantum state, which is called quantum information II. The nature of quantum information is the show of quantum events and their correlated ways. Quantum information is a kind of certainty and order. Quantum information can be divided into quantum informationⅠand quantum informationⅡ.. Quantum InformationⅠjust only a phenomenonal definition, it does not go deeply into the nature of the information. Therefore, the elimination of uncertainty can not be seen as the nature of quantum information itself . In the process of quantum teleportation, the source of quantum information (such as quantum state , a and b are coefficients) is delivered to the receiver, what is the essence of quantum information? From the point of view of quantum information theory, quantum state represents quantum information, quantum state is the state of quantum system (or microscopic particles) or quantum events. in the quantum state , what quantum states disclose the quantum information does not be the absolute size of quantum information, but the relationship, since the coefficients a and b satisfy the condition , and it do not be important numerical a and b, but between their relative size and relationship, which reflects the correlated ways between a and b. The connotation of quantum InformationⅠand quantum information Ⅱ offers support for the common view of classical information concept. Which is more deeply to disclose the nature of quantum information for both of them? Obviously, quantum information Ⅱ reflects the nature of quantum information. Quantum reality and quantum information are unified. What the wave function expresses is quantum reality. The wave function is unified of quantum information and quantum reality. There is no quantum reality, there is no quantum information. Because of the information and reality are unified, and quantum information different from classical information, so we can deduce that quantum reality is different from classical reality, and quantum computing differs from classical computing. In the classical parallel computing, the value calculated in different circuits respectively, but in parallel quantum computing the value calculated in one circuit, which is the essential difference between classical and quantum parallel computing. Many worlds interpretation of quantum mechanics does not mean that the difference between quantum and classical disappears: (1) Superposition in the microscopic world is very different from classical macroscopic physical world, so it is impossible that the superposition principle is fit for quantum world used for the classical world; (2) "To perform a quantum measurement, quantum world can be split up numerous classical world" is not supported by any experience and evidence; (3) Each branches of quantum computing are in quantum states, and quantum states are coherent, holistic, and some even entangled. Nevertheless, it is impossible for classical computing to achieve the quantum computing’s specific features; (4) The essential differences between quantum and the classical are decided by the development history of quantum mechanics and quantum information theory. The differences between quantum and the classical is really established by the quantum theory, concepts and their experiments that include Heisenberg’s matrix mechanics of Schrodinger’s wave equation, uncertainty principle of quantum mechanics and quantum entanglement phenomena and so on. They are completely different from the classical physical theories, concepts and experiments. Figure 1. Quantum information processing (see PDF version for the Figure). Conclusions This fruitful work gives an discussion of quantum concept that is the quantum information is the elimination of quantum uncertainty, which is called quantum information I and quantum information is the show (Zeigt) of quantum state, which is called quantum information II. Quantum information II reflects the nature of quantum information. The nature of quantum information is the show of quantum events and their correlated ways. Acknowledgments This research work of this paper is supported by 2011 the Philosophy and Social Sciences Foundation of the Ministry of Education of P. R. China (Project Number: 11JZD007) " Studies of the development trend of contemporary technological philosophy" . References and Notes Weiner, N., Cybernetics and Society. Houghton Mifflin Company, 1950. Shannon, C. E., The Mathematical Theory of Communication. The Bell System Technical Journal. 1948, Vol.27, pp.379-423, 623-656. Kornwachs K., Jacoby K., Introduction: What’s new about information? In Kornwachs K., Jacoby K.eds. Information. Berlin: Akademic Verlag GmbH. 1996. Bouwmeester, D. Pan, J.-W.，et al. Experimental Quantum Teleportation. Nature. 1997. 390. Bennett C. H. and Di Vinecenzo D. P. quantum information and computation, Nature, 2000, 404. Einstein, A. Podolsky B., and Rosen, N. Can Quantum-Mechanical Description of Physical Reality Be Considered Complete? Physical Review. 1935,47. Nielsen, M. A. Chuang, I. L., Quantum Computation and Quantum Information. Cambridge University Press, 2000. Duwell, A. Quantum information does not exist. Studies in History and Philosophy of Modern Physics，2003, (34). Berta, M. Christandl, M. Colbeck, R., et al. The uncertainty principle in the presence of quantum memory. Nat. Phys., 2010, (6). Caves， M. and Fuchs，C. A. 1996. Quantum information：how much information in a state vector?. preprint quant-ph/9601025. Barrow, J., et al, Science and Ultimate Reality: Quantum Theory, Cosmology and Complexity. Cambridge University Press. 2004. Yongde Zhang, Principles of Quantum Information Physics. Beijing: Science Press. 2006. Wheeler, J. A., At Home in the Universe. New York: Springer-Verlag. 1996. Guolin Wu, Quantum Entanglement And Its Philosophical Meaning, Studies in Dialectics of Nature, 2005, (7). Guolin Wu, A Detailed Philosophical Inquiry of the Quantum Information, Philosophical Researches. 2014, (8). Guolin Wu, Philosophical Connotation of quantum information Technology. Philosophical Trend. 2013, (8).
Summary form only given, as follows. Gives a system theoretic approach to the concept of quantum computing. A quantum computer is envisaged to be a system of quantum circuits, acting on a state space, which is a finite-say 2/sup n/-dimensional-complex Hilbert space. The circuitry is a sequence of unitary transforms U/sub t/ /spl epsiv/ SU(2/sup n/) followed by a measurement. These transforms, so-called quantum gates, are controlled by a classical computer, usually especially electromagnetic fields. The state space of a quantum computer has the structure of a Hermitian vector space. Thus it allows "simultaneous" superposition of orthogonal basis states (corresponding to classical states) with the possibility of constructive and destructive interference between different paths of computation. This principle allows the usage of so-called entangled states by preparing the superposition of special "bent" configurations of basis vectors in the product Hilbert space, e.g., as they are known from error control and cryptography. This latter "entanglement" not only promises to make a quantum computer much more powerful than a probabilistic one, but it also allows a method of parallelism. The reason for this lies not only in the fact that the 2/sup n/ dimensional Hilbert space is the n-fold tensor product of 2-dimensional spaces as it is given by spin-1/2-particles, like photons, representing a quantum bit. First of all, we shall address the fact that the power of quantum computing lies in the properties of entangled states as opposed to those of separable states which essentially would resemble classical circuits without giving the feature of exponential speed-up. We shall briefly describe possible physical realisations of quantum (optic, electronic, magnetic,...) devices allowing the engineering of Hamiltonians needed for quantum systems. Basic quantum gates, especially the quantum Horner-Toffoli gate will be discussed to display the principles and methodology for designing quantum circuits. An outlook towards the possible availability of nano- and mesoscopic technologies supporting this new architecture in future generations concludes based on a speculative worst/best case forecast of possible applications, e.g., in public key and conventional cryptography.