The relationship of quantum physics and language

The great CERN physicist Ian Bell once wrote a short reflective paper called “Speakable and unspeakable in quantum physics”. He introduced this paper by quoting the opening of Koestler’s Sleepwalkers: “the manner in which some of the most important individual discoveries were arrived at reminds one of a sleepwalker’s performance”. He added “I speak in a very low voice”. It was an extraordinary thing for a highly respected scientist to say. He goes on to talk about his own Bell’s Theorem as “a gross violation of relative causality”. 

At first glance, Bell’s evidently ambivalent feelings about the interpretation of his own work, at least, seem unjustified. The Theorem is a cornerstone proof of a phenomenon known as the ‘entanglement’ of particles. Entanglement describes the interrelationship of two particles. Once associated, it is said that the spin of one particle can be instantly determined from the spin of the other. They are therefore said to be entangled. That seems simple, and Bell’s theorem is a well tested proof, so what is unspeakable about it? 

Bell partly answers the question himself: Entanglement “has a very surprising feature: the consequences of events at one place propagate to other places faster than the speed of light.”

It may be surprising, but why is it unspeakable?

To answer this, it is necessary to understand that there is no such ‘thing’ as a ‘particle’. This may seem even more surprising, but if you think about it, it is difficult to imagine otherwise. There is no generally accepted definition of a particle, other than as ‘the smallest thing’ or sometimes just ‘fundamental’. A particle has never been observed, measured, or directly detected. It has no smaller constituents so we cannot describe it in terms of its behaviour, mass or matter. Nobody can say for certain what a particle ‘is’.  For this reason, in quantum physics, a particle is only ever a probability, and any quality associated with a particle is therefore expressed as an amount of probability. This fact is so central to quantum science that it takes its name after the calculation of these ‘quanta’, or amounts, of probability.

The non existence of particles as certain objects calls many things into question. 

One of these things is the language we are using. What does the word ‘particle’ refer to in quantum physics? We understand what a conventional particle is, so we might say that we are using the word as a metaphor. A ‘Quantum particle’ is not actually a particle, but since a we understand that a particle is a very small thing,  we understand the word metaphorically. It is a special kind of metaphor though. It uses one state of existence in observable reality as a metaphor for another which is a state of probability. This is extremely confusing, because it is a state of quite a different order of ‘being’. It is as if we called ghosts ‘humans’. using ‘human‘ as a metaphor for ’ghost’. That would be strange, and would create a confusion of the same order.

While it is tempting to dismiss this metaphorical displacement as esoteric, it presents a serious linguistic problem. It is blurring basic ontological distinctions. And it affects all the explanatory language we have used to describe quantum events. What does it mean, for instance, to talk about ‘spin’? If a particles is too small to see or describe, how can it be said to spin? And then, if we can’t observe a particle at all, how can we know if it is entangled with another one, or where either of them are afterwards? If a quantum particle is a metaphor, then so are spin and entanglement.

Physicists can answer these questions using complicated maths, and the answers mostly work. “It works” is something you hear quantum scientists say a lot to justify what they do. However, what is key is that there is no necessary connection between the language and the object supposedly described. That is what Bell meant by ‘unspeakable’. It is also a further signal of a “gross breakdown” of causality.

The dislocation of language from probabilistic science might have ‘worked’ up to a point, but unsurprisingly it can also be deeply unhelpful and highly misleading

Richard Feynman was another brilliant and famous quantum physicist. One of his proposals, made in the 60s, was that the instant communication of information brought about by ‘entanglement’ might be used to create a ‘quantum computer’, which would have a performance and speed vastly surpassing that of conventional computers. Unsurprisingly, this idea was enthusiastically adopted. But it has not yet ‘worked’, except possibly as a mathematical concept. Much of the problem with the building of a quantum computer has been the deceptively promising language. Normally, even if metaphorical, quantum language is led by the maths, but Feyman’s intervention reversed this cart and horse. To posit an entire functionality is to move a first cause which does not exist. The words ‘quantum computer’ relate to a classical concept which leads to expected forms and actions. But these must then be displaced, just as ‘particle’ is displaced, in an acknowledgement that a quantum computer might be and do something quite different. This is evidenced as soon as we attempt to describe what a quantum computer might do. 

A quantum computer, of course,  would use a quantum bit, or a ‘qubit’.  Wikipedia says “a qubit is a basic unit of quantum information– the quantum version of the classic physically realised with a two-state device.”

Simple, until you think about what a two state device might actually be, and why we might be discussing one. A two state device proposes the use of ‘superposition’. That is, simultaneous existence in two possible states. But herein lies the great difficulty. Simultaneous probabilities of course exist as quanta, and in this sense simultaneous states exist. But while we can superpose probabilities, probabilities are not objects. So ‘a two state device’ is part of the same metaphorical language as the quantum terms of ‘particle’, ‘spin’ and ‘entanglement’. And a qubit is a metaphorical bit, closely related, if not identical, to probability quanta.

The blind alley this leads us into is summed up by Wiki as follows:

“Quantum mechanics allows the qubit to be in a coherent superposition of multiple states simultaneously, a property that is fundamental to quantum mechanics and quantum computing.”

In order for this to make sense it would need to be written something like this: 

“Quantum mechanics allows metaphorical bits to be in a coherent superposition of multiple states of probability simultaneously, a property that is fundamental to quantum mechanics and the metaphorical functions of a quantum computer”.

This might seem disappointing. However, these metaphorical functions may be of great interest. Imagination is often a metaphorical function, and closely associated with  it are emotions and empathetic states. Far from closing the project down, the use of more precise language is quite simple, may offer much better direction, and allows a glimpse of the possible.