Every once in a while, a technology comes along with so much potential that people can't seem to stop talking about it. That's fun and exciting, but it can also be confusing. Not all of the people who opine really know what they're talking about and, as the cacophony of voices increases to a loud roar, it's hard to know what to believe.
We're beginning to hit that point with quantum computing. Listen to some and you imagine that you'll be strolling down to your local Apple store to pick one up any day now. Others will tell you that these diabolical machines will kill encryption and bring global commerce to a screeching halt. None of this is true.
What is true though is that quantum computing is not only almost unimaginably powerful, it is also completely different than anything we've ever seen before. You won't use a quantum computer to write emails or to play videos, but the technology will significantly impact our lives over the next decade or two. So here's a basic guide to what you really need to know about it.
Computing in 3 Dimensions
Quantum computing, as any expert will tell you, uses quantum effects such as superposition and entanglement to compute, unlike digital computers that use strings of ones and zeros. Yet quantum effects are so confusing that the great physicist Richard Feynman once remarked that nobody, even world class experts like him, really understands them.
So instead of quantum effects, think of quantum computing as a machine that works in three dimensions rather than two-dimensions like digital computers. The benefits of this should be obvious, because you can fit a lot more stuff into three dimensions than you can into two, so a quantum computer can handle vastly more complexity than the ones we're used to.
Another added benefit is that we live in three dimensions, so quantum computers can simulate the systems we deal with every day, like those in materials and biological organisms. Digital computers can do this to some extent, but some information always gets lost translating the data from a three dimensional world to a two dimensional one, which leads to problems.
I want to stress that this isn't exactly an accurate description of how quantum computers really work, but it's close enough for you to get the gist of why they are so different and, potentially, so useful.
Coherence and Error Correction
Everybody makes mistakes and the same goes for machines. When you think of all the billions of calculations a computer makes, you can see how even an infinitesimally small error rate can cause a lot of problems. That's why computers have error correction mechanisms built into their code to catch mistakes and correct them.
With quantum computers the problem is much tougher because they work with subatomic particles and these systems are incredibly difficult to keep stable. That's why quantum chips need to be kept within a fraction of a degree of absolute zero. At even a sliver above that, the system "decoheres" and we won't be able to make sense out of anything.
It also leads to another problem. Because quantum computers are so prone to error, we need a whole lot of quantum bits (or qubits) for each qubit that performs a logical function. In fact, with today's technology, we need more than a thousand physical qubits (the kind that are in a machine) for each qubit that can reliably perform a logical function.
This is why most of the fears of quantum computing killing encryption and destroying the financial system are mostly unfounded. The most advanced quantum computers today only have about 50 qubits, not nearly enough to crack anything. We will probably have machines that strong in a decade or so, but by that time quantum safe encryption should be fairly common.
Building Practical Applications
Because quantum computers are so different, it's hard to make them efficient for the tasks that we use traditional computers for because they effectively have to translate two-dimensional digital problems into their three-dimensional quantum world. The error correction issues only compound the problem.
There are some problems, however, that they're ideally suited to. One is to simulate quantum systems, like molecules and biological systems, which can be tremendously valuable for people like chemists, materials scientists and medical researchers. Another promising area is large optimization problems for use in the financial industry and helping manage complex logistics.
Yet the people who understand those problems know little about quantum computing. In most cases, they've never seen a quantum computer before and have trouble making sense out of the data they generate. So they will have to spend some years working with quantum scientists to figure it out and then some more years explaining what they've learned to engineers who can build products and services.
We tend to think of innovation as if it is a single event. The reality is that it's a long process of discovery, engineering and transformation. We are already well into the engineering phase of quantum computing--we have reasonably powerful machines that work--but the transformation phase has just begun.
The End of the Digital Revolution and a New Era of Innovation
One of the reasons that quantum computing has been generating so much excitement is that Moore's Law is ending. The digital revolution was driven by our ability to cram more transistors onto a silicon wafer, so once we are not able to do that anymore, a key avenue of advancement will no longer be viable.
So many assume that quantum computing will simply take over where digital computing left off. It will not. As noted above, quantum computers are fundamentally different than the ones we are used to. They use different logic, require different computing languages and algorithmic approaches and are suited to different tasks.
That means the major impacts from quantum computers won't hit for a decade or more. That's not at all unusual. For example, although Apple came out with the Macintosh in 1984, it wasn't until the late 90s that there was a measurable bump in productivity. It takes time for an ecosystem to evolve around a technology and drive a significant impact.
What's most important to understand, however, is that the quantum era will open up new worlds of possibility, enabling us to manage almost unthinkable complexity and reshape the physical world. We are, in many ways, just getting started.