Quantum of solace: even physicists are still scratching their heads
Your editorial on quantum physics (30 August) starts with a quote from Richard Feynman – “nobody understands quantum mechanics” – and then says “that is no longer true”. One of us (Norman Dombey) was taught quantum theory by Feynman at Caltech; the other (John Charap) was taught by Paul Dirac at Cambridge. Quantum theory was devised by several physicists including Dirac, Erwin Schrödinger and Werner Heisenberg in the 1920s and 1930s, and Dirac made their work relativistic.
It is absurd to say that quantum mechanics is now understood whereas it was not 50 years ago. There have of course been advances in our understanding of quantum phenomena, but the conceptual framework of quantum physics remains as it was. The examples you give of nuclear plants, medical scans and lasers involve straightforward applications of quantum mechanics that were understood 50 years ago.
The major advance in the understanding of quantum physics in this period is a theorem of John Bell from Cern, which states that quantum physics cannot be local – that is to say that it permits phenomena to be correlated at arbitrarily large distances from each other. This has now been demonstrated experimentally and leads to what is known as quantum entanglement, which is important in the development of quantum computers. But even these ideas were discussed by Albert Einstein and coworkers in 1935.
