It is shown that a lack of knowledge about the measurements of a physical system gives rise to a nonclassical probability calculus for this physical system. It is also shown that the nonclassical probability calculus of quantum mechanics can be interpreted as being the result of a lack of knowledge about the measurements. Examples are given of macroscopic real systems that have a nonclassical probability calculus. A macroscopic real system that has a quantum probability calculus is also given, and more specifically a model for the spin of a spin‐ 1/2 particle is constructed. These results are analyzed in light of the old hidden variable problem.

1.
J.
von Neumann
,
Grundlehren, Math. Wiss.
XXXVIII
, (
1932
).
2.
J. S.
Bell
,
Rev. Mod. Phys.
38
,
447
(
1966
).
3.
J. M.
Jauch
and
C.
Piron
,
Helv. Phys. Acta.
36
,
827
(
1963
).
4.
A. M.
Gleason
,
J. Math. Mech.
6
,
885
(
1957
).
5.
S.
Kochen
and
E. P.
Specker
,
J. Math. Mech.
17
,
59
(
1967
).
6.
S. P.
Gudder
,
Rev. Mod. Phys.
40
,
229
(
1968
).
7.
L. Accardi, Rend. Sem. Mat. Univ. Politech. Torino 1982, 249.
8.
L.
Accardi
and
A.
Fedullo
,
Lett. Nuovo Cimento
34
,
161
(
1982
).
9.
D.
Aerts
,
Lett. Nuovo Cimento
34
,
107
(
1982
);
“The physical origin of the EPR paradox,” in Proceedings of the Colloquium on “Open Questions in Quantum Physics,” in Bari, edited by Tarozzi and A. van der Merwe (Reidel, Dordrecht, 1985);
“How to violate Bell inequalities and the Bell locality hypothesis by means of macroscopical systems,” in Proceedings of the Symposium on the Foundations of Modern Physics, 50 years of the Einstein‐Podolsky‐Rosen Gedankenexperiment (Joensuu, Finland, 1985).
10.
D. Aerts, “A possible explanation for the probabilities of quantum mechanics and example of a macroscopical system that violates Bell inequalities,” in Recent Developments in Quantum Logic, edited by P. Mittelstaedt and E. W. Stachow, in Grundlagen der Exakten Naturwissenschaften, band 6 (Wissenschaftverlag, Bibliografisches Institut, Mannheim, 1985).
11.
S. P.
Gudder
,
J. Math. Phys.
11
,
431
(
1970
).
This content is only available via PDF.
You do not currently have access to this content.