What are key developments in your field?
The ability to solve large, complex problems always has an impact on the future of mankind at whichever stage man is at. In a sense, that's the ability to solve a large problem that involves something that's happening in the world around us. It's a little like peeking a little bit into the future because an understanding of the world around us, we can learn how to control it and for better or for worse. So I would say that the development of quantum computers, in particular, opens up new vistas in terms of control as a physical world because we know that we will be able to use it for computing and simulating very large, complex physical systems that we cannot now simulate with these. And so we can't study them and we can't understand them. It may eventually lead to understanding complex biological systems. It may lead to a greater understanding of systems as complex as the brain, and which would really, I think, truly revolutionize our understanding of us as human beings.
Will we have nanomachines soon?
There's a lot of work done in nanofabrication towards building nanoscale molecular machines, unrelated to trying to control quantum behavior of systems at the nanoscale. Certainly, there's a lot of work, for instance, in building molecular computers, which are the direct analog of the computers we use today, just scaled down to atoms and molecules. And those computers are likely be built before quantum computers. They would become general purpose computers. I think there's a desire to make everything smaller and smaller in general in the world around us. and that's partly because it's cute, in addition to saving space. So I think there will be a gradual rise of devices that operate in the nanoscale, whether they're quantum or classical.
What is Schroedinger's cat?
The concept of Schroedinger 's cat, as introduced by Schroedinger in the 1930s, was an attempt to explain why quantum mechanics actually gives a different view of history. We play little "what if" games. We say, "Well, what if Napoleon had dropped dead in 1802?" And then we imagine in our fantasies the things that might have happened as a result of that what if. Quantum mechanics says that these branchings in histories are actually almost objective, they are actually real, and Schröedinger introduced a little-thought experiment in which an atom, which quantum mechanically can be in a superposition of two different states, gets entangled. Actually, his example was of a radioactive atom, which can be in a superposition of either having decayed or having not decayed. He invented a game in which the decay or not decay of the atom resulted in a cat being killed or not killed. By that progression of events, that cat itself was in the superposition, in this special state of having been alive and not alive, and so real historical events can be placed into this funny superposition state and quantum mechanics says that in some sense, all versions of history get played out all at once.
Talk about factoring.
We in the community are still working on the question of what kinds of problems are solvable, very efficiently, on quantum computers. The famous one is that of extracting prime factors. That is, given an integer like 15, doing a computation to find that its prime factors are 3 and 5. That's a simple computation for 15, and it's a very hard computation for a 100-digit number, but there are procedures on quantum computers that are very efficient, vastly more efficient than on any conventional computer for solving that problem. We are finding that there are a whole host of other number theory problems, many of which are fairly abstract, but all in some way related to the factoring problem for which this kind of efficiency is also available, this kind of quantum computing efficiency, and new discoveries continue to be made.
What are differences between industry and academia in science?
I think they're very different from one another, and it's valuable for our society that they both go on. I'm in a unique position here because I've been visiting Caltech for the last half year, and I'm on sabbatical leave from industry since I work for IBM Research. The constraints of the corporate world are very, very different. In the corporate world, typically you're very much more aware of potential applications or potential implications of the work that you do and the corporation is constantly asking you, politely, but consistently and insistently sometimes: What is this good for? Why is it good for us, in fact? And fortunately, with a corporation like IBM, they're willing for that answer to be couched in a setting of 20 years or so. So if they want to know why is my work in quantum computing good for them in 20 years, I have plenty of answers for them. In many other corporate settings the question is why is this good for us in three months, and then I would have a hard time answering, and that's what skews a lot of the research that goes on in industry. But still, there is in a sense a greater freedom, maybe illusory, but the feeling of greater freedom with being at a university.
How do we know that quantum mechanics is real?
People like Einstein and other famous physicists have objected to it. At a gut level, they feel that it's aesthetically wrong; it doesn't fit with their intuition. They don't want it to be the case. And yet quantum mechanics is without a doubt the most heavily, frequently, and completely confirmed physical theory that has ever been created in terms of being verified by experiment and time and time and time again. Now that, to me, suggests that that's strong evidence in its favor because if there were some way that it could be shown wrong, people would've loved to have shown it wrong. There's a fact that quantum mechanics is so counterintuitive and yet so successful is, to me, one of the strongest recommendations for a theory.
What do you think will be the greatest advancement quantum mechanics will allow us to make?
I think the greatest advance that we're going to make is to construct a new way of thinking about how the world operates, a quantum digital way of thinking about how the world works because at bottom the world is quantum mechanical and the world operates by representing and processing information. So I think that what we could really do is by the sense of how we'll make a big influence is by bringing to the quantum world the revolution and thought and perception that the information world has brought to us already.