Quantum Mechanics is one of the most successful physical theories of the last century. It explains physical phenomena from the smallest to the largest lengthscales. Despite this triumph, quantum mechanics is often perceived as a mysterious theory, involving superposition states that are alien to our everyday Big World. The construction of a future quantum computer relies on our ability to manipulate quantum superposition states in qubits. In this thesis it is shown that these qubits can be subtly influenced by the physics associated with spontaneous symmetry breaking. This process destroys the quantum nature of the qubit and renders it useless for quantum computation. An even more fundamental problem with quantum superpositions is that they cannot be reconciled with the theory of general relativity. In the end of this thesis a model is proposed which describes the effective, deteriorating, influence of gravity on quantum states, thus suggesting a path toward the demise of quantum mechanics in the big world.
Quantum Mechanics is one of the most successful physical theories of the last century. It explains physical phenomena from the smallest to the largest lengthscales. Despite this triumph, quantum mechanics is often perceived as a mysterious theory, involving superposition states that are alien to our everyday Big World. The construction of a future quantum computer relies on our ability to manipulate quantum superposition states in qubits. In this thesis it is shown that these qubits can be subtly influenced by the physics associated with spontaneous symmetry breaking. This process destroys the quantum nature of the qubit and renders it useless for quantum computation. An even more fundamental problem with quantum superpositions is that they cannot be reconciled with the theory of general relativity. In the end of this thesis a model is proposed which describes the effective, deteriorating, influence of gravity on quantum states, thus suggesting a path toward the demise of quantum mechanics in the big world.
Quantum Mechanics is one of the most successful
physical theories of the last century. It explains physical
phenomena from the smallest to the largest lengthscales.
Despite this triumph, quantum mechanics is often perceived
as a mysterious theory, involving superposition states that are
alien to our everyday Big World.
The construction of a future quantum computer relies on
our ability to manipulate quantum superposition states in
qubits. In this thesis it is shown that these qubits can be subtly
influenced by the physics associated with spontaneous symmetry
breaking. This process destroys the quantum nature of
the qubit and renders it useless for quantum computation.
An even more fundamental problem with quantum superpositions
is that they cannot be reconciled with the theory of
general relativity. In the end of this thesis a model is proposed
which describes the effective, deteriorating, influence of
gravity on quantum states, thus suggesting a path toward the
demise of quantum mechanics in the big world.
Quantum Mechanics is one of the most successful physical theories of the last century. It explains physicalphenomena from the smallest to the largest lengthscales. Despite this triumph, quantum mechanics is often perceived as a mysterious theory, involving superposition states that are alien to our everyday Big World.In Quantum Mechanics and The Big World the connection between Quantum Mechanics and the Classical World, which we see around us every day, is investigated. The quantum origin of large systems turns out to continuously influence their behaviour. One of the consequences discussed in this thesis, is that qubits (the basic building blocks of a future quantum computer) can hold on to their stored quantum information only for a given time. After that time the qubit will be effectively reduced to just an ordinary bit.Another important connection between quantum mechanics and classical physics is the way in which gravity could influence quantum mechanical particles. In this thesis one particular idea about this influence is proposed.
Quantum mechanics occupies a unique position in the history of science. It has survived all experimental tests to date, culminating with the most precise comparison of any measurement to any theory – a 1987 measurement of the electron's magnetic moment, or gyromagnetic ratio g e = 2.002 319 304 39 (Van Dyck et al. 1987), agreeing with QED theory to 12 digits. Despite this and other dramatic successes of quantum mechanics, its foundations are often questioned, owing to the glaring difficulties in reconciling quantum physics with the classical laws of physics that govern macroscopic bodies. If quantum mechanics is indeed a complete theory of nature, why does it not apply to everyday life? Even Richard Feynman (1982), a fierce defender of quantum mechanics, memorably stated that: We have always had a great deal of difficulty in understanding the world view that quantum mechanics represents … Okay, I still get nervous with it … It has not yet become obvious to me that there is no real problem. I cannot define the real problem, therefore I suspect there's no real problem, but I'm not sure there's no real problem. In the dawn of the twenty-first century, John A. Wheeler's big question “Why the quantum?” has returned to the forefront of physics with full steam. Advances in experimental physics are beginning to realize the same thought-experiments that proved helpful to Einstein, Bohr, Heisenberg, Schrödinger, and the other founders of quantum mechanics.
Quantum mechanics was developed in the early 20th century as a computational algorithm to organize and predict the strange results of a wide variety of experiments involving the microscopic world (molecules, atoms, elementary particles), which appeared random but had a predictable probabilistic distribution. Despite its overwhelming success, the conceptual foundations of this algorithm remain unclear and extremely controversial. How can we connect the microscopic world described by quantum mechanics with the macroscopic world of our daily experience? What is the role of observers in this connection? Why don't strange quantum phenomena occur on macroscopic scales? How can we explain the nonlocal nature of quantum phenomena? In this article I will present some attempts to answer these and other basic questions, which constitute different theories with completely different worldviews, commenting on their strengths and weaknesses. We will conclude that quantum theory is still under construction, as there is no consensual formulation. Its development is a fundamental problem in contemporary physics, and in thought in general.
For over nine decades, quantum mechanics has profoundly shaped our understanding of nature, offering explanations for the stability of atoms, the formation of mole cules, the properties of materials, and phenomena such as light or radioactivity. It is essential to modern technologies—from microchips to lasers—and underpins the physics of elementary particles. Yet, despite its successes, it remains a deeply mysterious theory, confronting a central enigma: why does the quantum world behave so differently from everyday reality? Elements such as superposition and quantum entanglement—which allow particles to exist simultaneously in multiple states or remain interconnected regardless of distance—contradict classical world intuitions. This gap between microscopic and macroscopic behavior has given rise to what is known as the “measurement problem,” raising fundamental questions about the nature of reality. Diverging interpretations have led to two major schools of thought: anti-realism, promoted by Niels Bohr, which holds that reality depends on the observer and their interaction with measurement instruments; and realism, supported by Albert Einstein, which argues that quantum mechanics is incomplete and that eality exists independently of observation. Bohr’s complementary philosophy and Heisenberg’s uncertainty principle were central to the formulation of the “Copenhagen interpretation,” which became dominant in the 20th century. However, the persistent opposition of scientists like Einstein and Schrödinger inspired generations of physicists to seek a unification between quantum mechanics and relativity, culminating in new theories such as loop quantum gravity and string theory. Thus, the debate between realism and anti-realism remains alive, and philosophy continues to play a crucial role in exploring the new foundations of physics.
The early twentieth century was a revolutionary time in the history of physics. People often think of Einstein's special theory of relativity of 1905, which changed our conceptions of time and space. But among physicists, quantum mechanics is usually regarded as an even more radical change in our thinking about the physical world. Quantum mechanics, which was developed between 1900 and 1926, began as a theory of atoms and light but has now become the framework in terms of which all basic physical theories are expected to be cast. We need quantum ideas not only to understand atoms, molecules, and elementary particles, but also to understand the electronic properties of solids and even certain astronomical phenomena such as the stability of white dwarf stars. The theory was radical in part because it introduced probabilistic behavior as a fundamental aspect of the world, but even more because it seems to allow mutually exclusive situations to exist simultaneously in a “quantum superposition.” We will see later that the possibility of quantum superposition is largely responsible for a quantum computer's distinctive advantage over an ordinary computer. The present chapter is devoted to introducing the basic principles of quantum mechanics. There are essentially four components of the mathematical structure of quantum mechanics. We need to know how to represent (i) states, (ii) measurements, (iii) reversible transformations, and (iv) composite systems. We will develop the first three in stages, starting with a very simple case – linear polarization of photons – and working toward the most general case.