The Universe Within (25 page)

The transition from analog to digital sound — from records and tapes to CDs and MP3s — caused a controversy, which continues to this day, about whether a digital reproduction is less rich and interesting to listen to than an analog version. By using more and more digital bits, one can mimic an analog sound to any desired accuracy. The fact remains that analog sound is inherently more subtle and less jarring than digital. Certainly, even in this digital age, analog instruments show no signs of going out of fashion.

Life's
DNA
code is digital. Its messages are written in three-letter “words” formed from a four-letter alphabet. Every word codes for an amino acid, and each sentence codes for a protein, made up of a long string of amino acids. The proteins form the basic machinery of life, part of which is dedicated to reading and transcribing
DNA
into yet more proteins. Although it is indeed amazing that all of the extravagant diversity and beauty of life is encoded in this way, it is also important to realize that the
DNA
code itself is not in any way alive.

Although the genetic basis for life is digital, living beings are analog creatures. We are made of plasmas, tissues, membranes, controlled by chemical reactions that depend continuously on concentrations of enzymes and reactants. Our
DNA
only comes to life when placed in an environment with the right molecules, fluids, and sources of energy and nutrients. None of these factors can be described as digital. New
DNA
sequences only arise as the result of mutations and reshufflings, which are partly environmental and partly quantum mechanical in origin. Two of the key processes that drive evolution — variation and selection — are therefore
not
digital. The main feature of the digital component of life —
DNA
— is its persistent, unambiguous character; it can be reproduced and translated into
RNA
and protein accurately and efficiently. The human body contains tens of trillions of cells, each with an identical copy of the
DNA
. Every time a cell divides, its
DNA
is copied.

It is tempting to see the digital
DNA
code as the fundamental basis of life, and our living bodies as merely its “servants,” with our only function being to preserve our
DNA
and to enable its reproduction. But it seems to me that one can equally well argue that life, being fundamentally analog, uses digital memory simply to preserve the accuracy of its reproduction. That is, life is a happy combination of mainly digital memory and mainly analog operations.

At first sight, our nerves and brains might appear to be digital, since they either fire or do not in response to stimuli, just as the basic digital storage element is either 0 or 1. However, the nerve-firing rate can be varied continuously, and nerves can fire either in synchrony or in various patterns of disarray. The concentrations and flows of biomolecules involved in key steps, such as the passage of signals across synapses, are analog quantities. In general, our brains appear to be much more nuanced and complex systems than digital processors. This disjuncture between our own analog nature and that of our computers is quite plausibly what makes them so dissatisfying as companions.

Although analog information can always be accurately mimicked by using a sufficient number of digital bits, it is nevertheless a truism that analog information is infinitely richer than digital. Quantum information is infinitely richer again. Just one qubit of quantum information is described by a continuum of values. As we increase the number of qubits, the number of continuous values required to describe them grows exponentially. The state of a 300-qubit quantum computer (which might consist of a chain of just 300 atoms in a row) would be described by more numbers than we could represent in an analog manner, even if we used the three-dimensional position of every single one of the 10
90
or so particles in the entire visible universe.

The ability of physical particles to carry quantum information has other startling consequences, stemming from entanglement, in which the quantum state of two particles is intrinsically interlinked. In Chapter Two, I described how, in an Einstein–Podolsky–Rosen experiment, two particles fly apart with their spins “entangled,” so that if you observe both particles' spin along some particular axis in space, then you will always find one particle's spin pointing up while the other points down. This correlation, which Einstein referred to as “spooky action at a distance,” is maintained no matter how far apart the particles fly. It is the basis for Bell's Theorem, also described in Chapter Two, which showed that the predictions of quantum theory can never be reproduced by classical ideas.

Starting in the 1980s, materials have been found in which electrons exhibit this strange entanglement property
en masse
. The German physicist Klaus von Klitzing discovered that if you suspend a piece of semiconductor in a strong magnetic field at a very low temperature, then the electrical conductance (a measure of how easily electric current flows through the material) is quantized. That is, it comes in whole number multiples of a fundamental unit. This is a very strange result, like turning on a tap and finding that water will flow out of it only at some fixed rate, or twice that rate, or three times the rate, however you adjust the tap. Conductance is a property of large things: wires and big chunks of matter. No one expected that it too could be quantized. The importance of von Klitzing's discovery was to show that in the right conditions, quantum effects can still be important, even for very large objects.

Two years later, the story took another twist. The German physicist Horst Störmer and the Chinese physicist Dan Tsui, working at Bell Labs, discovered that the conductance could also come in rational fractions of the basic unit of conductance, fractions like
1
⁄
3
,
2
⁄
5
,
and
3
⁄
7
. The U.S. theorist Robert Laughlin, working at Stanford, interpreted the result as being due to the collective behaviour of all the electrons in the material. When they become entangled, they can form strange new entities whose electric charge is given in fractions of the charge of an electron.

Ever since these discoveries, solid state physicists have been discovering more and more examples of systems in which quantum particles behave in ways that would be classically impossible. These developments are challenging the traditional picture of
individual
particles, like electrons, carrying charge through the material. This picture guided the development of the transistor, but it is now seen as far too limited a conception of the possible states of matter. Quantum matter can take an infinitely greater variety of forms. The potential uses of these entirely new states of matter, which, as far as we know, never before formed in the universe, are only starting to be explored. They are likely to open a new era of quantum electronics and quantum devices, capable of doing things we have never seen before.

IN THE EARLY TWENTIETH
century, the smallest piece of matter we knew of was the atomic nucleus. The largest was our galaxy. Over the subsequent century, our most powerful microscopes and telescopes have extended our view down to a ten-thousandth the size of an atomic nucleus and up to a hundred thousand times the size of our galaxy.

In the past decade, we have mapped the whole visible universe out to a distance of nearly fourteen billion light years. As we look farther out into space, we see the universe as it was longer and longer ago. The most distant images reveal the infant universe emerging from the big bang, a hundred-thousandth of its current age. It was extremely uniform and smooth, but the density of matter varied by around one part in a hundred thousand from place to place. The primordial density variations appear to take the same form as quantum fluctuations of fields like the electromagnetic field in the vacuum, amplified and stretched to astronomical scales. The density variations were the seeds of galaxies, stars, planets, and, ultimately, life itself, so the observations seem to be telling us that quantum effects were vital to the origin of everything we can now see. The Planck satellite, currently flying and due to announce its results soon, has the capacity to tell us whether the very early universe underwent a burst of exponential expansion. Over the coming decades, yet more powerful satellite observations may be able to tell whether there was a universe before the big bang.

Very recently, the Large Hadron Collider has allowed us to probe the structure of matter on the tiniest scales ever explored. In doing so, it has confirmed the famous Higgs mechanism, responsible for determining the properties of the different types of elementary particles. Beyond the Large Hadron Collider, the proposed International Linear Collider will probe the structure of matter much more accurately on these tiniest accessible scales, perhaps revealing yet another layer of organization, such as new symmetries connecting matter particles and forces.

With experiments like the Large Hadron Collider and the Planck satellite, we are reaching for the inner and outer limits of the universe. Equally significant, with studies of quantum matter on more everyday scales, we are revealing the organization of entangled levels of reality more subtle than anything so far seen. If history is any guide, these discoveries will, over time, spawn new technologies that will come to dominate our society.

Since the 1960s, the evolution of digital computers has been inexorable. Moore's law has allowed them to shrink and move progressively closer to our heads, from freezer-sized cabinets to desktops to laptops to smartphones held in our hands. Google has just announced Project Glass, a pair of spectacles incorporating a fully capable computer screen. With the screen right next to your eye, the power requirements are tiny and the system can be super-efficient. No doubt the trend will continue and computers will become a more and more integral part of our lives, our bodies, and our selves.

Having access to vast stores of digital information and processing power is changing our society and our nature. Our future evolution will depend less and less on our biological genes, and more and more on our abilities to interact with our computers. The future battle for survival will be to program or be programmed.

However, we are analog creatures based upon a digital code. Supplementing ourselves with more and more digital information is in this sense evolutionarily regressive. Digital information's strongest feature is that it can be copied cheaply and accurately and translated unambiguously. It represents a reduction of analog information, the “dead” blueprint or memory of life, rather than the alive analog element.

On the other hand, quantum information is infinitely deeper, more subtle and delicate than the analog information familiar to us. Interacting with it will represent a giant leap forward. As I have already explained, a single qubit represents more information than any number of digital bits; three hundred qubits represents more information than could be encoded classically using every particle in the universe. But the flip side is that quantum information is extremely fragile. The laws of quantum physics imply that it cannot be copied, a result known as the “no cloning” theorem. Unlike classical computers, quantum computers will not be able to replicate themselves. Without us, or at least some classical partner, they will not be able to evolve.

So it seems that a relationship between ourselves, as analog beings, and quantum computers may be of great mutual benefit, and it may represent the next leap forward for evolution and for life. We shall provide the definiteness and persistence, while quantum computers embody the more flighty, exploratory, and wide-ranging component. We will ask the questions, and the quantum computer will provide the answers. Just as our digital genes encode our analog operations, we, or our evolutionary successors, shall be the “operating system” of quantum life.

In the same way our
DNA
is surrounded by analog machinery bringing it to classical life, we will presumably become surrounded by quantum computers, making us even more alive. The best combinations of people and quantum computers will be the most successful, and will survive and propagate. With their vast information-processing capacities, quantum computers may be able to monitor, repair, or even renew our bodies. They will allow us to run smart systems to ensure that energy and natural resources are utilized with optimal efficiency. They will help us to design and oversee the production of new materials, like carbon fibres for space elevators and antimatter technologies for space propulsion. Quantum life would seem to have all the qualities needed to explore and understand the universe.

· · ·

WHILE THE POSSIBILITY OF
a coming “Quantum Age” is exciting, nothing is guaranteed about the future: it will be what we make of it. For a sharp dose of pessimism, let us turn to a remarkable woman visionary whose main targets were the Romantic notions of her age, the Victorian “Age of Wonder” and exploration, and the Industrial Revolution.

Mary Shelley was the daughter of one of the first feminists, Mary Wollstonecraft, a philosopher, educator, and the author, in 1792, of
A Vindication of the Rights of Women;
her father was William Godwin, a radical political philosopher. During childbirth, Wollstonecraft contracted a bacterial infection, and she died soon after. Throughout her life, Shelley continued to revere her mother. She was raised by her father, and when sixteen years old she became involved with Percy Bysshe Shelley, one of England's most famous Romantic poets. Percy was already married, and their relationship caused a great scandal. After his first wife committed suicide, Percy married Mary. They had four children (two before they were married), although only the last survived. The first was premature and died quickly. The second died of dysentery and the third of malaria, both during their parents' travels in Italy.