Friday, November 13, 2009

The Age of Entanglement

Louisa Gilder speaking at Telecosm Conference

My physicist friend the late Heinz Pagels believed that the 20th Century would not be remembered for its wars or its Moon walks but as the century in which humans first encountered the "Cosmic Code"--Heinz's pet name for the mysteries of quantum mechanics. The Cosmic Code, according to Pagels, is the unhuman language Nature speaks that brings into existence the material world.

I am currently reading a new popular book (thanks, Earl Crockett) which retells the exciting story of humanity's initial discovery of the Cosmic Code--Louisa Gilder's remarkable The Age of Entanglement now available in paperback. Gilder's book is remarkable in two ways: first for her solid grasp of the quantum concepts and her ease of explanation and second, for her decision to frame these concepts as conversations between the great men who struggled to formulate and understand this almost incomprehensible breakthrough into Nature's storehouse of mysteries. Louisa does not entirely invent these conversations but assembles them from letters and unpublished papers. Her method gives an impressive immediacy to these ideas which mere exposition would lack. Louisa's technique gives one the feeling of eavesdropping on the private lives of the discoverers of the greatest of Nature's secrets.

One delightful example of Louisa's conversations involves two physicists climbing a mountain as they are expressing their frustration at Niels Bohr's new quantum model of the atom which seemed to violate every rule of classical physics they had so painstakingly learned in school. And yet Bohr's model not only worked but it worked splendidly, explaining detailed features of the spectrum of hydrogen that were previously utterly mysterious. On the mountain top the two physicists take a solemn vow--that if this quantum craziness continued, they would both drop out of physics. The craziness did indeed continue; it baffles us to this day. And the two physicists did not drop out but pushed past their confusion to aid in the birth of the new quantum science.

Unusual for a book about physics, Louisa's book is crowded with people. Most of my favorite physics heroes come alive here in sketches, descriptions and witty conversations--Niels Bohr, Werner Heisenberg, Albert Einstein, Erwin Schrödinger, Wolfgang Pauli, John Clauser and John Stewart Bell and many, many others.

Louisa is a true mistress of metaphor. Many times I found myself thinking, "O, I wish I could have said that so well." Here is how she handles why physicists continued then (and indeed continue today) to work on the quantum theory despite its deep and troublesome foundational questions.

It became more and more obvious that despite some odd details, ignored like the eccentricities of a general who is winning a war, quantum mechanics was the most accurate theory in the history of science.

Erwin Schrödinger was the first to discover quantum entanglement--a voodoo-like connection that persists unchanged between two particles after interaction no matter how distant they are separated. Schrödinger, using the equation that bears his name, had no trouble describing one quantum particle moving in three dimensions of space, but when he extended his equation to describe two particles he got not TWO WAVES moving in three dimensions but ONE WAVE moving in six dimensions -- a description which choreographs their otherwise separate motions (seemingly faster than light) by what Einstein dismissively called "spooky action at a distance". Quantum entanglement, said Schrödinger, is not A NEW FEATURE of quantum theory, it is THE NEW FEATURE that distinguishes it most from the classical physics we all learned in school.

Louisa Gilder argues that just as the nineteenth Century was the era when the new theory of Thermodynamics and the practical development of steam engines teamed up to produce the Industrial Revolution, so we are now witnessing the birth of a similar mutually reinforcing interaction between the theory of quantum entanglement and the practice of quantum computing. We are at the very beginning, she says, of an era whose technology we cannot yet foresee. Assembling today the rudiments of primitive quantum machines that tap directly into Nature's Cosmic Code, we are on the brink, Louisa Gilder eloquently proclaims, of a bottom-up revolutionary Age of Quantum Entanglement.

Sketch of Erwin Schrödinger by Louisa Gilder