LIVING IN THE QUANTUM WORLD
• Quantum mechanics is commonly said to be a theory of microscopic things: molecules, atoms, subatomic particles.
• Nearly all physicists, though, think it applies to everything, no matter what the size. The reason its distinctive features tend to be hidden is not a simple matter of scale.
• Over the past several years experimentalists have seen quantum effects in a growing number of macroscopic systems.
• The quintessential quantum effect, entanglement, can occur in large systems as well as warm ones—including living organisms—even though molecular jiggling might be expected to disrupt entanglement.
According to standard physics textbooks,quantum mechanics is the theory of the microscopic world. It describes particles,
atoms and molecules but gives way to ordinary classical physics on the macroscopic scales of pears, people and
planets. Somewhere between molecules and pears lies a boundary where the strangeness of quantum behavior ends and the
familiarity of classical physics begins. The impression that quantum mechanics is limited to the microworld permeates the
public understanding of science. For instance, Columbia University physicist Brian Greene writes on the first page of his
hugely successful (and otherwise excellent) book The Elegant Universe that quantum mechanics “provides a theoretical
framework for understanding the universe on the smallest of scales.” Classical physics,
which comprises any theory that is not quantum, including Albert Einstein’s theories of relativity, handles the largest of
Yet this convenient partitioning of the world is a myth. Few modern physicists think that classical physics has equal status with quantum mechanics; it is but a useful approximation of a world that is quantum at all scales. Although quantum effects may
be harder to see in the macroworld, the reason has nothing to do with size per se but with the way that quantum systems
interact with one another. Until the past decade, experimentalists had not confirmed that quantum behavior persists on a
macroscopic scale. Today, however, they routinely do. These effects are more pervasive than anyone ever suspected. They
may operate in the cells of our body.
Quantum mechanics is not just about teeny particles. It applies to things of all sizes: birds, plants, maybe even people
By Vlatko Vedral, Scientific American Ned ed. nr. 4 2011
Quantum Entanglement, Photosynthesis and Better Solar Cells
As nature’s own solar cells, plants convert sunlight into energy via photosynthesis. New details are emerging about how the process is able to exploit the strange behavior of quantum systems, which could lead to entirely novel approaches to capturing usable light from the sun.
All photosynthetic organisms use protein-based “antennas” in their cells to capture incoming light, convert it to energy and direct that energy to reaction centers—critical trigger molecules that release electrons and get the chemical conversion rolling. These antennas must strike a difficult balance: they must be broad enough to absorb as much sunlight as possible yet not grow so large that they impair their own ability to shuttle the energy on to the reaction centers.
This is where quantum mechanics becomes useful. Quantum systems can exist in a superposition, or mixture, of many different states at once. What’s more, these states can interfere with one another—adding constructively at some points, subtracting at others. If the energy going into the antennas could be broken into an elaborate superposition and made to interfere constructively with itself, it could be transported to the reaction center with nearly 100 percent efficiency.
A new study by Mohan Sarovar, a chemist at the University of California, Berkeley, shows that some antennas—namely, those found on a certain type of green photosynthetic bacteria—do just that. Moreover, nearby antennas split incoming energy between them, which leads not just to mixed states but to states that are entangled over a broad (in quantum terms) distance. Gregory ¬Scholes, a chemist at the University of Toronto, shows in a soon to be published study that a species of marine algae utilizes a similar trick. Interestingly, the fuzzy quantum states in these systems are relatively long-lived, even though they exist at room temperature and in complicated biological systems. In quantum experiments in the physics lab, the slightest intrusion will destroy a quantum superposition (or state).
These studies mark the first evidence of biological organisms that exploit strange quantum behaviors. A better understanding of this intersection of microbiology and quantum information, researchers say, could lead to “bioquantum” solar cells that are more efficient than today’s photovoltaics.
By Michael Moyer /2009
Letters to Nature – Wave–particle duality of C60 molecules
Quantum superposition lies at the heart of quantum mechanics and gives rise to many of its paradoxes. Superposition of de Broglie matter waves1 has been observed for massive particles such as electrons2, atoms and dimers3, small van der Waals clusters4, and neutrons5. But matter wave interferometry with larger objects has remained experimentally challenging, despite the development of powerful atom interferometric techniques for experiments in fundamental quantum mechanics, metrology and lithography6. Here we report the observation of de Broglie wave interference of C60 molecules by diffraction at a material absorption grating. This molecule is the most massive and complex object in which wave behaviour has been observed. Of particular interest is the fact that C60 is almost a classical body, because of its many excited internal degrees of freedom and their possible couplings to the environment. Such couplings are essential for the appearance of decoherence7, 8, suggesting that interference experiments with large molecules should facilitate detailed studies of this process.
Markus Arndt, Olaf Nairz, Julian Vos-Andreae, Claudia Keller, Gerbrand van der Zouw & Anton Zeilinger Institut für Experimentalphysik, Universität Wien, Boltzmanngasse 5, A-1090 Wien, Austria / 1999
Sustained Quantum Coherence and Entanglement in the Avian Compass
Abstract: In artificial systems, quantum superposition and entanglement typically decay rapidly unless cryogenic temperatures are used. Could life have evolved to exploit such delicate phenomena? Certain migratory birds have the ability to sense very subtle variations in Earth’s magnetic field. Here we apply quantum information theory and the widely accepted “radical pair” model to analyze recent experimental observations of the avian compass. We find that superposition and entanglement are sustained in this living system for at least tens of microseconds, exceeding the durations achieved in the best comparable man-made molecular systems. This conclusion is starkly at variance with the view that life is too “warm and wet” for such quantum phenomena to endure.
Journal reference: Phys. Rev. Lett. 106, 040503 (2011)
Erik Gauger, Elisabeth Rieper, John J. L. Morton, Simon C. Benjamin, Vlatko Vedral
Decoding Reality: The Universe as Quantum Information is a popular science book by Vlatko Vedral published by Oxford University Press in 2010. Vedral examines information theory and proposes information as the most fundamental building block of reality. He argues what a useful framework this is for viewing all natural and physical phenomena. In building out this framework the books touches upon the origin of information, the idea of entropy, the roots of this thinking in thermodynamics, the replication of DNA, development of social networks, quantum behaviour at the micro and macro level, and the very role of indeterminism in the universe. The book finishes by considering the answer to the ultimate question: where did all of the information in the Universe come from? The ideas address concepts related to the nature of particles, time, determinism, and of reality itself.
Something from Nothing”
Vedral believes in the principal that information is physical. Creation ex nihilo comes from Catholic dogma, the idea being that god created the universe out of nothing. Vedral says that invoking a supernatural being as an explanation for creation does not explain reality because the supernatural being would have to come into existence itself too some how presumably from nothing (or else from an infinite regression of supernatural beings), thus of course the reality can come from nothing without a supernatural being. Occam’s razor principle favours the simplest explanation. Vedral believes information is the fundamental building block of reality as it occurs at the macro level (economics, human behaviour etc) as well as the subatomic level. Vedral argues that information is the only candidate for such a building block that can explain its own existence as information generates additional information that needs to be compressed thus generating more information. ‘Annihilation of everything’ is a more fitting term than creation ex nihilo Vedral states, as compression of possibilities is the process of how new information is created.
“Back to Basics: Bits and Pieces”
Shannon entropy or information content measured as the surprise value of a particular event, essentially inversely proportional to the logarithm of the event’s probability, i = log(1/p). Claude Shannon’s information theory arising from research at Bell labs, building upon George Boole’s digital logic. As information theory predicts common and easily predicted words tend to become shorter for optimal communication channel efficiency while less common words tend to be longer for redundancy and error correction. Vedral compares the process of life to John von Neumann’s self replicating automata. These are enduring information carriers that will survive wear and tear of the individual by producing copies that can in turn go on to produce more copies.
“Quantum Schmuntum: Lights, Camera, Action!”Vedral examines the basis of quantum information, the qubit, and examines one-time pad quantum cryptography as the most secure form of encryption because of its uncomputability. Quantum entanglement demonstrates the importance of mutual information in defining outcomes in a reality.
“Surfing the Waves: Hyper-Fast Computers”
Quantum computers offer a search advantage over classical computers by searching many database elements at once as a result of quantum superpositions. A sufficiently advanced quantum computer would break current encryption methods by factorizing large numbers several orders of magnitude faster than any existing classical computer. Any computable problem may be expressed as a general quantum search algorithm although classical computers may have an advantage over quantum search when using more efficient classical algorithms. The issue with quantum computers is that a measurement must be made to determine if the problem is solved which collapses the superposition. Vedral points out that unintentional interaction with the environment can be mitigated with redundancy, and this would be necessary if we were to scale up current quantum computers to achieve greater utility, i.e. to utilize 10 qubits have a 100 atom quantum system so that if one atom decoheres a consensus will still be held by the other 9 for the state of the same qubit.
Whose Information is It, Anyway?”
The information content of the universe as measured in bits or qubits. Vedral uses the initial effort of Archimedes of Syracuse in calculating the amount of sand that could theoretically fit inside the universe and compares it to a modern day attempt to calculate the bit content of the universe. Vedral however sees this content as ultimately limitless as possibly maximum entropy is never reached as compression of complexity is an open ended process and random events will continue to occur. As Vedral sees information as the ultimate building block of physical reality, he speculates that information originating at any scale can force outcomes in all other scales to abide where mutual information is shared. For example a human performed macro-level scientific test in search of a behaviour in a quantum particle could set parameters for that type of particle in the future when subjected to a similar test.
“Destruction ab Toto: Nothing from Something”
The information basis for creation ex nihilo. According to John von Neumann, starting trivially from an empty set of numbers an infinite sequence of numbers can bootstrap their way out. An empty set creates the number 1 by observing an empty set within itself which is enough of a basis for distinguishability. It creates the number 2 by observing an empty set within the second empty set and the number 1, and so on. Vedral sees this as not creation as but data compression as every event of a reality breaks the symmetry of the pre-existing formlessness. Science is the process of describing a large amount of observed phenomena in a compressed programmatic way to predict future outcomes, and in this process of data compression science creates new information by eliminating all contrary possibilities to explain that phenomena.
It is all Information, including the origin of God’
“Quantum mechanics brings all kinds of shades of grey between the binary digits” Professor Vlatko Vedral grapples with the behavior of energy and matter at subatomic scales, and this has led him to ask some bigger questions including why are we here? And what does it all mean? The 39-year-old, originally from Belgrade, passionately believes units of information – not particles – are the building blocks of humanity and everything that surrounds us. Information, he maintains, is what came before everything else. It is akin to God.
What information is important at the quantum level, and how does it help us understand the origins of the universe?
At first sight, all types of information look very different from one another. For example, contrast thermodynamics – how chaotic a system is – with the information in your genome. You’d say: what on earth is the relationship between these two types of information? One looks much more orderly, the living system, while the other is disorder. But it’s actually one and the same information… you actually need very little to define the concept of information in the first place. When you strip out all the unnecessary baggage, at the core is the concept of probability. You need randomness, some uncertainty that something will happen, to let you describe what you want to describe. Once you have a probability that something might happen, then you can define information. And it’s the same information in physics, in thermodynamics, in economics.
Quantum physicists think of the universe as being made up of particles and strings. Are you suggesting that information is superior to these physical properties?
It depends on what you ultimately aim to explain. In science, we start with a certain basic set of laws, like the ones described by particle physics. These laws rely on quantum mechanics and relativity and so on. We start from them and try to describe everything else – subatomic, atomic, larger objects and, ultimately, the universe. But the simple question raised at the end is: where do these laws come from?
In science, we’re criticised for being unable to go beyond these laws to explain their origins. It’s what philosophers call an infinite regression: you give me an explanation, but I can ask where that comes from. We never seem to be able to end the list of questions. I think information is the only concept capable of almost explaining itself, of closing this circle.
How are you not conflating information with a God or another deity?
The common answer is that there was some kind of original creator of this information. The trouble is that this answer doesn’t really solve anything because as a physicist I’d also like to understand this being itself. I’d like to explain the origin of God. And then you encounter the same infinite regression. For a scientist, “Why is there a universe? Well, because something even more complicated created it the way it is” isn’t an explanation. We want a better answer than that. You can argue that science will never get there, that it’s an open-ended enterprise. Maybe this is faith.
But we also have a set of beliefs in science. We believe in one method of understanding the ultimate, secure truth: the scientific method. We make a conjecture. We try to refute it as far as we can. Those conjectures that survive longest are those that currently define the laws of nature. We’re not dogmatic about it at all; if you have compelling evidence that something is wrong, we are very happy to upgrade ourselves to the new theory. Of course you can always challenge me and ask why I believe this is the only way to understand the world. The only answer is that it makes sense to me. I find it better than anything else.
How can you explain the emergence of free will, of faith, of any subjective construct if information defined in your theory is binary, a yes or a no?
The things you describe are far too complicated to easily derive within physics, but I do believe one day that we will be able to explain complicated phenomena such as love, for example. I just don’t think anyone yet knows how to approach it. But quantum mechanics does bring all kinds of shades of grey between the binary digits.
The perspective of classical physics governed by Newtonian laws describes the world as deterministic, and that there is no randomness. But the key concept behind information is probability: if you could compute and predict everything, as we could if the world really was classical, there would be no concept of surprise and there’d be no information. Everything would be clear, from the beginning to the end of the universe. Somehow we need a genuine randomness that can’t be explained by anything more fundamental. That’s the key concept for explaining everything out of nothing.
To reduce humanity to this idea of mathematical quantification implies that we can be recreated by having the right recipe and ingredients.
We can take a particle of light, a photon, and we can recreate this photon in a different lab that’s hundreds of kilometres away. We can do the same thing with an atom, and smaller objects.
Human beings are ultimately nothing but a collection of atoms. If we apply this same teleport scheme, resulting in another copy of yourself somewhere else, what does that mean? Would you really be yourself? Or would the teleported self be another person with the same physical features who might not feel the same? As far as we know, this would have to be your self there. But we can only wait until an experiment is done to test this.
Are we at an important point in our human history in terms of how we generate, synthesise and understand information?
A good analogy is if you put yourself in the perspective of the people who, in the early 1920s, had just discovered the laws of quantum physics. They said it’s extremely difficult to apply this to even the simplest of atoms. Then along comes someone else who says: “I have a piece of solid – 10 to the power of 24 atoms – and you’re telling me you’re finding it hard to understand a single atom? How on earth will we understand a whole solid?” In fact, this happened very shortly afterwards. It’s called solid-state physics and it’s the basis of all modern technology.
Being negative by saying that it looks too complicated has always been refuted by scientists. That’s why I believe there is hope for us to understand more and more.
A physicist argues that information is at the root of everything
ONE of the most elusive goals in modern physics has turned out to be the creation of a grand unified theory combining general relativity and quantum mechanics, the two pillars of 20th-century physics. General relativity deals with gravity and time and space; quantum mechanics with the microscopic workings of matter. Both are incredibly successful in their own domains, but they are inconsistent with one another.
For decades physicists have tried to put the two together. At the heart of the quest lies the question, of what is the universe made? Is it atoms of matter, as most people learned in school? Or some sort of energy? String theory, currently a popular idea, holds that the universe is made up of tiny vibrating strings. Other equally esoteric candidates abound. Indeed, cynics claim that there are as many grand unified theories as there are theoretical physicists attempting unification.
Now Vlatko Vedral, examines the claim that bits of information are the universe’s basic units, and the universe as a whole is a giant quantum computer. He argues that all of reality can be explained if readers accept that information is at the root of everything.
So what is information?
Mr Vedral’s notion of information is not the somewhat fuzzy concept most people have of it, but a precise mathematical definition that owes itself to Claude Shannon, an American mathematician considered to be the father of “information theory”. Shannon worked at Bell Labs, at the time the research arm of AT&T, a telephone giant, and in the 1940s became interested in how much information could be sent over a noisy telephone connection. This led him to calculate that the information content of any event was proportional to the logarithm of its inverse probability of occurrence. (Unlike many popular-science books that eschew equations, Mr Vedral includes a couple and tries his best to explain them to the reader.) What does the equation mean? As Mr Vedral points out, it says that an unexpected, infrequent event contains much more information than a more regular happening.
Once he has defined information, Mr Vedral proceeds to show how information theory can be applied to biology, physics, economics, sociology and philosophy. These are the most interesting parts of the book. Of particular note is the chapter on placing bets. Mr Vedral gives a good description of how Shannon’s information theory can be applied to winning at blackjack or in buying shares (Shannon and his friends made fortunes in Las Vegas as well as on the stockmarket). And his exposition of climate change and how to outwit the CIA make entertaining reading. One quibble: Mr Vedral often digresses from the point at hand, so the overall effect tends to be a bit meandering.
Mr Vedral’s professional interests lie in quantum computing and quantum information science, which use the laws of quantum mechanics respectively to build powerful computers and render codes unbreakable. There is a lot of discussion of both, which is very welcome because there are not many popular science books that cover these relatively young fields. Quantum computers, as Mr Vedral points out, “are not a distant dream”. Though still rudimentary, “they can solve some important problems for us that conventional computers cannot.”
Unusually for a physicist, Mr Vedral spends a fair bit of time talking about religious views, such as how God created the universe. He asks whether something can come out of nothing. Throughout the ages philosophers and theologians have debated this question with respect to Judeo-Christian faiths, in which dogma holds that the world was created from the void, creation ex nihilo. Others side with King Lear who tells Cordelia that “Nothing can come of nothing.” Mr Vedral makes a persuasive argument for a third option.
The Universe as Quantum Information
Since the start of the 20th century, theoretical physics has provided a rich seam for authors keen to explain in popular terms the nature of “reality”. We already know, courtesy of Albert Einstein, Niels Bohr and others, that reality is, to quote JBS Haldane, “queerer than we imagine and queerer than we can imagine”.
The reality we can imagine involves elementary particles – protons, neutrons and electrons and even more elementary particles such as quarks and neutrinos. These are reassuringly physical, even if they exhibit the disturbing quantum properties of being in two places at once and able to communicate over astronomical distances.
Now Vlatko Vedral, seeks to persuade us that at its most fundamental, reality is encoded in information. This alone, he argues, is enough to explain quantum mechanics as well as biological inheritance, sociology and the stock market. (Interestingly, Claude Shannon, the “father” of information theory, made a fortune out of shares but died with his investment secrets intact.)
“The reader may not agree with my ultimate view of encoding reality,” Vedral writes, “but hopefully he or she will find the discussion of the separate pillars (biology, economics, gambling and so on) valuable in themselves.” Certainly he provides conclusive evidence that gambling on the lottery is a waste of money.
An immediate question, however, is how to define “information”. Most of us have a rough idea. Vedral has a very precise, scientific definition: it is the logarithm of the inverse of the probability of an event. Or, more simply, the more unexpected an event, the more information it contains.
On this somewhat counterintuitive foundation, he builds castles of mathematical logic: “In biology, for example, an event could be a genetic modification stimulated by the environment. In economics, an event could be a fall in a share price. In quantum physics, it could be the emission of light by a laser when it is switched on. No matter what the event is, you can apply information theory to it. That is why I will be able to argue that information underlies every process we see in nature,” he says.
Vedral writes in an amiable, unaffected style but this is a difficult book for the non-specialist. He has the slightly irritating habit of starting to explain a key point, then wandering off into an anecdote, in the manner of a lecturer diverted by a passing thought. The sense that one is reading an introductory text to a university course is reinforced by a series of “take-home” lessons at the end of each chapter.
Unusually, perhaps, for a work of this kind, the author devotes space to religious views of the existence of God. I particularly like the Cappadocian idea that we cannot say that God exists because existence is a human notion and as such may not apply to God. Vedral thinks this view reminiscent of the laws of physics. Queerer, indeed, than anything we can imagine.
Synopsis of the book of Vedral
The book explains the world as being made up of information. The Universe and its workings are the ebb and flow of information. We are all transient patterns of information, passing on the recipe for our basic forms to future generations using a four-letter digital code called DNA. In this engaging and mind-stretching account, Vlatko Vedral considers some of the deepest questions about the Universe and considers the implications of interpreting it in terms of information. He explains the nature of information, the idea of entropy, and the roots of this thinking in thermodynamics. He describes the bizarre effects of quantum behaviour – effects such as ‘entanglement’, which Einstein called ‘spooky action at a distance’ and explores cutting edge work on the harnessing quantum effects in hyperfast quantum computers, and how recent evidence suggests that the weirdness of the quantum world, once thought limited to the tiniest scales, may reach into the macro world. Vedral finishes by considering the answer to the ultimate question: where did all of the information in the Universe come from? The answers he considers are exhilarating, drawing upon the work of distinguished physicist John Wheeler and his concept of “it from bit”. The ideas challenge our concept of the nature of particles, of time, of determinism, and of reality itself.