t follows I shall explain brie fly and in an elementary way why I considerthe methods of quantum mechanics fundamentally unsatisfactory

herefore inclined to believe that the description of quantum mechanics inthe sense of Ia has to be regarded as an incomplete and indirect description of reality,to be replaced at some later date by a more complete and direct one.

It follows that every statement about S2 which we arriveat as a result of a complete measurement of S1 has to be valid for the system S2, evenif no measurement whatsoever is carried out on S1. This would mean that allstatements which can be deduced from the settlement of ψ2 or ψ2' mustsimultaneously be valid for S2

This is, of course, impossible, if ψ2, ψ2', etc. shouldrepresent different real states of affairs for S2, that is, one comes into conflict with theIb interpretation of the ψ-function

an operation, however, can have no direct in fluence on the physical realityin a remote part R2 of space

Einstein cannot accept the fundamental fact of "entangled" systems explained to himby Schrödinger, that they cannot be separated

principle II, i.e. the independent existence of the real stateof affairs existing in two separate parts of space R1 and R2

from the point of view of quantum mechanics alone, this does not presentany difficulty. For, according to the choice of measurement to be carried out on S1, adifferent real situation is created, and the necessity of having to attach two or moredifferent ψ-functions ψ2, ψ2', ... to one and the same system S1 cannot arise.

sulting ψ2 depends on this choice, so that di fferent kinds of (statistical)predictions regarding measurements to be carried out later on S2 are obtained,according to the choice of measurement carried out on S1

This means, from the pointof view of the interpretations of Ib, that according to the choice of completemeasurement of S1 a different real situation is being created in regard to S2, which canbe described variously by ψ2, ψ2', ψ2'', etc

Any "measurement" instantaneously collapses the two-particle wave function ψ12.There is no "later" collapse when measuring the "other" system S2

make the assertion that the interpretation of quantum mechanics(according to Ib) is not consistent with principle II

llowing idea characterizes the relative independence of objects far apart inspace (A and B): external influence on A has no direct influence on B; this is known asthe 'principle of contiguity', which is used consistently only in the field theory. If thisaxiom were to be completely abolished, the idea of the existence of (quasi-) enclosedsystems, and thereby the postulation of laws which can be checked empirically in theaccepted sense, would become impossible

Anessential aspect of this arrangement of things in physics is that they lay claim, at acertain time, to an existence independent of one another, provided these objects 'aresituated in different parts of space'. Unless one makes this kind of assumption aboutthe independence of the existence (the 'being-thus') of objects which are far apart fromone another in space which stems in the first place from everyday thinking - physicalthinking in the familiar sense would not be possible. It is also hard to see any way offormulating and testing the laws of physics unless one makes a clear distinction of thiskind

the concepts ofphysics relate to a real outside world, that is, ideas are established relating to thingssuch as bodies, fields, etc., which claim a 'real existence' that is independent of theperceiving subject

we assume (in the sense of interpretation Ib) that the ψ-function completely describes a real state of affairs, and that two (essentially) differentψ-functions describe two different real states of affairs, even if they could lead toidentical results when a complete measurement is made. If the results of themeasurement tally, it is put down to the influence, partly unknown, of the measurementarrangements

According to this point of view, two ψ-functions which differ in more thantrivialities always describe two different real situations

italone does justice in a natural way to the empirical state of affairs expressed inHeisenberg's principle within the framework of quantum mechanics

(b) In reality the particle has neither a definite momentum nor a definite position;the description by ψ-function is in principle a complete description. The sharply-defined position of the particle, obtained by measuring the position, cannot beinterpreted as the position of the particle prior to the measurement. The sharplocalisation which appears as a result of the measurement is brought about onlyas a result of the unavoidable (but not unimportant) operation of measurement.The result of the measurement depends not only on the real particle situationbut also on the nature of the measuring mechanism, which in principle isincompletely known. An analogous situation arises when the momentum or anyother observable relating to the particle is being measured. This is presumablythe interpretation preferred by physicists at present

According to this point of view, the ψ-function represents an incompletedescription of the real state of affairs. This point of view is not the one physicistsaccept

der a free particle described at a certain time by a spatially restricted ψ-function (completely described - in the sense of quantum mechanics). According tothis, the particle possesses neither a sharply defined momentum nor a sharply definedposition. In which sense shall I imagine that this representation describes a real,individual state of affairs?

I imagine that this theory maywell become a part of a subsequent one, in the same way as geometrical optics is nowincorporated in wave optics: the inter-relationships will remain, but the foundation willbe deepened or replaced by a more comprehensive one.

Einstein’s objectively real view that aparticle has a position, a continuous path, and various propertiesthat are conserved as long as the particle suffers no interaction thatcould change any of those properties

It is impossible to predict in which of the two beams thephoton will be found

s Einstein’s “objective reality”sees it, an individual photon is always in a single quantum state!

This is to remind us that Einstein had long accepted thecontroversial idea that quantum mechanics is a statistical theory,despite the claims of some of his colleagues, notably Born, thatEinstein’s criticisms of quantum mechanics were all intended torestore determinism and eliminate chance and probabilities.