David Bohm’s research while affiliated with University of London and other places

Understanding Quantum Technologies Olivier Ezratty 2023 Key Takeaways Here are some key takeaways from Olivier Ezratty's book "Understanding Quantum Technologies" (2023 edition): Quantum technologies are rapidly advancing and have the potential to revolutionize computing, communications, sensing, and cryptography. Quantum computing is based on the principles of quantum mechanics, such as superposition and entanglement, which enable quantum computers to perform certain calculations exponentially faster than classical computers. There are several approaches to building quantum computers, including superconducting qubits, trapped ions, photonic qubits, and silicon spin qubits, each with its own advantages and challenges. Quantum algorithms, such as Shor's algorithm for factoring large numbers and Grover's algorithm for searching unstructured databases, can provide significant speedups over classical algorithms for certain problems. Quantum error correction is crucial for building large-scale, fault-tolerant quantum computers, as qubits are highly sensitive to noise and errors. Quantum communications, based on the principles of quantum key distribution (QKD), can provide provably secure communication channels that are resistant to eavesdropping. Quantum sensing and metrology can enable ultra-precise measurements of physical quantities, such as time, gravity, and magnetic fields, with applications in navigation, imaging, and fundamental science. Quantum technologies are attracting significant investments from governments, corporations, and venture capitalists worldwide, with a growing ecosystem of startups, research institutions, and industry partnerships. The development of quantum technologies faces several challenges, including scaling up quantum systems, improving qubit quality and coherence times, and developing efficient quantum algorithms and software. The societal and economic impact of quantum technologies is expected to be significant, with potential applications in drug discovery, materials science, optimization, machine learning, and cryptography, among others.

The relationship of mind and matter is approached in a new way in this article. This approach is based on the causal interpretation of the quantum theory, in which an electron, for example, is regarded as an inseparable union of a particle and afield. This field has, however, some new properties that can be seen to be the main sources of the differences between the quantum theory and the classical (Newtonian) theory. These new properties suggest that the field may be regarded as containing objective and active information, and that the activity of this information is similar in certain key ways to the activity of information in our ordinary subjective experience. The analogy between mind and matter is thus fairly close. This analogy leads to the proposal of the general outlines of a new theory of mind, matter, and their relationship, in which the basic notion is participation rather than interaction. Although the theory can be developed mathematically in more detail, the main emphasis here is to show qualitatively how it provides a way of thinking that does not divide mind from matter, and thus leads to a more coherent understanding of such questions than is possible in the common dualistic and reductionistic approaches. These ideas may be relevant to connectionist theories and might perhaps suggest new directions for their development.

Die übliche Deutung der Quantentheorie ist selbstkonsistent, enthält aber Annahmen, die nicht experimentell überprüft werden können, wie z. B. daß die vollständigst mögliche Beschreibung eines individuellen Systems durch eine Wellenfunktion erfolgt, die nur den wahrscheinlichen Ausgang tatsächlicher Messungen festlegt. Ob diese Annahme korrekt ist, kann nur durch den Versuch überprüft werden, eine andere Interpretation der Quantentheorie durch derzeit „verborgene“ Variable zu finden, die im Prinzip das exakte Verhalten eines individuellen Systems bestimmen, aber in der Praxis bei den heute möglichen Messungen herausgemittelt werden. In dieser und einer folgenden Arbeit soll eine Deutung der Quantentheorie durch derartige „verborgene Variable“ vorgeschlagen werden. Es zeigt sich, daß die hier vorgeschlagene Deutung zu genau denselben Ergebnissen für alle physikalischen Prozesse führt wie die übliche Deutung, sofern die mathematische Theorie ihre allgemeine Form beibehält. Dennoch führt die vorgeschlagene Deutung auf ein allgemeineres Begriffssystem als die übliche Deutung, da sie eine präzise und kontinuierliche Beschreibung aller Prozesse sogar auf dem Quantenniveau erlaubt. Das erweiterte Begriffssystem ermöglicht allgemeinere mathematische Formulierungen der Theorie als die übliche Deutung. Die gebräuchliche mathematische Formulierung scheint aber auf unlösbare Schwierigkeiten zu führen, wenn sie auf kleinere Abstände als 10−13 cm extrapoliert wird [A1]. Es wäre möglich, daß die hier vorgeschlagene Deutung zur Lösung dieser Schwierigkeiten benötigt wird. In jedem Fall beweist die bloße Möglichkeit einer derartigen Interpretation, daß eine exakte, rationale und objektive Beschreibung individueller Systeme auf dem Quantenniveau nicht notwendigerweise unmöglich ist.

We explore the possibilities of a new informal language, applicable to the microdomain, which enables such characteristics as superposition and discreteness to be introduced without recourse to the quantum algorithm. In terms of new notions that are introduced (e.g. ‘potentiation’ and ‘ensemblation’), we show that an experiment need no longer be thought of as a procedure designed to investigate a property of a ‘separately existing system’. Thus, the necessity of a sharp separation between the ‘system under observation’ and the ‘apparatus’ is avoided. Although the new language is very different from that of classical physics, classical notions appear as a special limiting case. This new informal language leads to a mathematical formalism which employs the descriptive terms of a cohomology theory with values in the integers. Thus our theory is not based on the use of a space-time description, continuous or otherwise. In the appropriate limit, the mathematical formalism contains certain features similar to those of classical field theories. It is therefore suggested that all the field equations of physics can be re-expressed in terms of our theory in a way that is independent of their spacetime description. This point is illustrated by Maxwell's equations, which are understood in terms of cohomology on a discrete complex. In this description, the electromagnetic four-vector potential and the four-current can be discussed in terms of an ‘ensemblation’ of discontinuous hypersurfaces or varieties. Since the cohomology is defined on the integers the charge is naturally discrete.

An answer is given to a recent criticizm by Fock, concerning our paper "Time in the Quantum Theory and the Uncertainty Relation for Time and Energy." It is proved that Fock's criticizm is wrong, and that our previous conclusion that energy can be measured in an arbitrarily short period of time is valid.