History of Quantum Theory

University of Sydney :: 31 May 2008

A one-day satellite meeting of the History of Quantum Physics project.

Venue : Organisers : Timetable : Abstracts : Enquiries

The workshop will be held in the Main Quadrangle Refectory (downstairs in the SW corner).

Guido Bacciagaluppi (Centre for Time, Sydney)
Kristian Camilleri (HPS, Melbourne)

The parting of the ways: early research on Quantum Gravity
Dean Rickles (HPS, Sydney)

In this talk I examine the earliest (pre-WWII) research on the problem of quantum gravity and show how it connects up to later work. Many of the main positions that can be discerned in the present research landscape can be found in this much earlier work.

The statistical interpretation according to Born and Heisenberg
Guido Bacciagaluppi (Centre for Time, Sydney)

At the 1927 Solvay conference Born and Heisenberg presented a joint report on quantum mechanics. I suggest that the significance of this report lies in that it contains a 'final' formulation of the statistical interpretation of quantum mechanics that goes beyond Born's original proposal. In particular, this formulation imports elements from Heisenberg's work as well as from the transformation theory of Dirac and Jordan. I suggest further a reading of Born and Heisenberg's position in which the wave function is an effective notion. This can make sense of a remarkable aspect of their presentation, namely the fact that the 'quantum mechanics' of Born and Heisenberg apparently lacks wave function collapse.

The other response to EPR: Heisenberg's "Ist eine deterministische Ergänzung der Quantenmechanik möglich?
Elise Crull (Philosophy, Notre Dame, IN)

While many are aware of Bohr's response to EPR, it is less well-known that Heisenberg also drafted a response in July 1935; it was never published, save as an addendum to a letter to Pauli.

In this talk, I present a synopsis of the paper and attempt to investigate in some depth the numerous issues of historical and philosophical significance that arise therein. Namely, in this paper Heisenberg gives what appears to be the first description of a contextual hidden variables theory, anticipating Bell by nearly thirty years. Furthermore, Heisenberg's argument for the completeness of quantum mechanics as presented in his 1935 rests heavily on his idea of the "Cut" between the classical and quantum regimes-an approach that shows interesting parallels to modern decoherence interpretations, as well as displays a vastly different approach to interpreting the formalism than Bohr. I argue that this provides further ammunition against the so-called "Copenhagen Interpretation".

Quantum states: From Schrödinger to decoherence
Max Schlosshauer (Physics, Melbourne)

The meaning of the wave function (or, more generally, quantum states) has been a point of contention since the early days of quantum mechanics. I will first recall Schrödinger's realist interpretation, the Born-Pauli interpretation, and some subsequent developments. Then I shall discuss to what extent decoherence may cast a new light on problems and open questions associated with these interpretations.

The quantum-classical transition: Bohr's doctrine of classical concepts and decoherence
Kristian Camilleri (HPS, Melbourne)

The problem of explaining how the essentially 'classical' features of the macro-world emerge from a quantum theory of the micro-world has been one of the central problems for the interpretation of quantum mechanics since the 1930s. Yet recent developments in the study of the entanglement between quantum systems and their environments have shed new light on the emergence of 'classicality' in quantum mechanics. This process, known as 'decoherence', has now been widely accepted and provides a deep insight into explaining why quantum superpositions effectively disappear in the macroscopic world - in other words why we don't encounter 'Schršdinger cats'. Decoherence is sometimes understood as marking a significant break with the 'Copenhagen interpretation of quantum mechanics', and in particular with Bohr's view of the indispensability of classical concepts, insofar as it provides a dynamical account of the emergence of 'classicality'. The natural question is then to ask to what extent such a research program may run counter to Bohr's assumptions of intrinsic, underivable classical concepts and of different, mutually contradictory descriptions as embraced by the complementarity principle.

In addressing this question, this paper provides a new insight into Bohr's view of the quantum-classical divide and his doctrine of classical concepts with the aim of analyzing its relationship to the decoherence-based program of emergent classicality. By drawing on a reconstruction of Bohr's doctrine of classical concepts, and by paying careful attention to a hitherto overlooked disagreement between Heisenberg and Bohr in the 1930s about the placement of the quantum-classical 'cut', it is possible to show that such Bohr's assumption about 'classicality' can be physically justified by appealing to decoherence. Here I also discuss early anticipations of the role of the environment in the quantum-classical problem in Heisenberg's writings. Finally we distinguish the different formulations of the doctrine of classical concepts which had emerged by the 1960s in an effort to present a nuanced assessment of the relationship between Bohr's views and decoherence that challenges oversimplified statements frequently found in the literature.

Last Update
30/5/08