Heisenberg cut

English

Alternative forms

• Heisenberg's cut

Etymology

Named after Werner Heisenberg, who contributed to the Copenhagen interpretation of quantum mechanics, and specifically to the theory of wavefunction collapse.

Noun

Heisenberg cut (plural Heisenberg cuts)

1. (quantum mechanics, philosophy of physics) A conceptualised division separating the quantum system being observed from the classical system that comprises the observer's information, knowledge and conscious awareness.
   • 2014, Henry P. Stapp, “Quantum Physics and Philosophy of Mind”, in Antonella Corradini, Uwe Meixner, editors, Quantum Physics Meets the Philosophy of Mind, Walter de Gruyter, page 9:

     The original "Copenhagen" way of describing the collapse process was tied to a mysterious thing called the "Heisenberg cut". Everything lying "below" this cut was supposed to be described in the mathematical language of quantum mechanics, whereas everything lying "above" the cut was described either in the language of classical physics, or in psychological or mental terms. […] A principal move made by von Neumann was to show that the Heisenberg cut could be moved all the way up, so that reality was unambiguously separated into a purely mental part, and a part described in the mathematical language of quantum mechanics.

   • 2018, Lars Jaeger, The Second Quantum Revolution, Springer, page 252:

     Another idea is to question the impermeability of the Heisenberg cut: Is the separation between the macro and micro worlds really as sharp as Heisenberg and Bohr assumed?

   • 2021, Carl S. Helrich, The Quantum Theory—Origins and Ideas, Springer, page 192:

     The location of the Heisenberg cut is arbitrary, but it must be at a point where classical physics assuredly holds.

Usage notes

• As a concept whose physical existence is uncertain, the Heisenberg cut is primarily of theoretical and philosophical interest.
• The observed quantum system (everything governed by the wavefunction) is said to be below the cut. The system of the observer is said to be above the cut.
• Interpretations of quantum mechanics that do not rely on the concept of wavefunction collapse do not require Heisenberg cuts.

Translations

conceptualised division between quantum and classical realms

• French: please add this translation if you can
• German: Heisenbergscher Schnitt m
• Italian: please add this translation if you can

Further reading

• De Broglie–Bohm theory on Wikipedia.Wikipedia
  • Pilot wave theory on Wikipedia.Wikipedia
• Wave function on Wikipedia.Wikipedia
• Schrödinger's cat on Wikipedia.Wikipedia
• Wave function collapse on Wikipedia.Wikipedia