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Photons do not exist, according to Geoff Jones of the University of
Sussex. Jones believes that it is ‘wrong, and unnecessary’ to describe light
in terms of small, localised particles. If he is right, the quantum world
is less mysterious than physicists would have us believe.

Jones has used his controversial idea to eliminate some of the confusion
surrounding quantum descriptions of the famous double-slit experiment, which
demonstrates that light can behave both as a wave and a particle (European
Journal of Physics, vol 15, p 170).

In the double-slit experiment, a beam of light passes through the two
slits and produces an interference pattern on a detector screen – a pattern
of light and dark bands. A similar kind of pattern is produced when water
waves pass through slits. The puzzle of quantum physics is that even when
the beam of light is so weak that it can be considered to be made of ‘particles
of light’ or photons, the spots of light made by individual photons arriving
at the screen eventually build up an interference pattern. How does each
photon (which common sense says can only go through one slit or the other)
‘know’ about the slit it does not go through, and direct itself to the appropriate
place on the detector screen?

Jones quotes many standard texts which highlight this phenomenon, described
by Richard Feynman as the ‘central mystery’ of the quantum world. He then
explains that they are all wrong. In his picture, an electromagnetic field
fills the entire experiment (in principle, the entire Universe), and ‘knows’
that there are two slits there. What actually travels through the experiment
is not a little particle, but a disturbance in the electromagnetic field.
What is ‘detected’ as a photon is the removal of one quantum or packet of
energy from the field. ‘The idea of a single ‘photon’ propagating is meaningless,’
says Jones.

Using a similar argument, Jones previously pointed out that the work
for which Einstein received his Nobel prize, the ‘proof’ that photons exist
based on the photoelectric effect, is similarly flawed. All that is proved
is that energy can only be added to or subtracted from the field in definite
units.

But, recently, some researchers have carried out the double slit experiment
using electrons, fired one at at a time, to build up an interference pattern.
How does Jones explain that? Although he does not discuss this version of
the experiment in his paper, he told New Å®ÉúСÊÓƵ that this is a ‘very
interesting problem, which can be tackled in several different ways’. He
favours the idea that electrons are real particles, and that their statistical
distribution after being fired through the two slits depends on a wave associated
with the electrons.

This echoes an interpretation of quantum mechanics based on the work
of David Bohm, long considered a maverick, but whose work is now seen as
a serious alternative to the standard ‘Copenhagen Interpretation’ of quantum
mechanics.

Intriguingly, Jones points out that in this picture although the interference
pattern produced by electrons will look like the interference pattern produced
by light to a first approximation, other properties of electrons should
produce ‘second order’ effects, which are, in principle, measureable. So
his claims could be tested. If he is right, all those textbooks that talk
about photons as particles will have to be rewritten, and many lecture courses
revised.