Instead of focusing on all the hurdles scientist face in their efforts to develop a quantum computer, let’s assume that there will come a day when we have accessible and efficient quantum computing services in the cloud. Services similar to the supercomputing cloud services we have today.
In other words, the power of quantum computing at everyone's reach all around the world. It's obvious that this would open many doors. It could also be dangerous. Interestingly enough, it’s not entirely irrational to assume that this could be reality within the foreseeable future.
We should not belittle the challenges involved in developing quantum computing. As the name implies, it makes use of quantum-mechanical phenomena and that kind of physics is seriously weird. Physicist Richard Feynman famously said "If you think you understand quantum mechanics, you don't understand quantum mechanics.”.
The good part is that the theory of quantum computing seems to hold water – at least according to most physicists and computer scientists. The bad part is that it's very difficult to actually construct a device that performs large-scale quantum computing. Why? Because in order to exploit the weird quantum properties of small particles we have to isolate them from their environment. Otherwise the desired properties sort of "washes away" in a process called quantum decoherence.
They Already Exist
Despite the challenges, experimental quantum computers already exist and experiments have been carried out in which quantum computational operations were executed on a small number of quantum bits, so called qubits.
There’s even a commercial company called D-Wave Systems, which manufactures and sells computers that seem to have quantum properties. Many have doubted the company, but at least Lockheed Martin, Google, and Nasa take them seriously, because they’ve all invested millions of dollars in D-Wave computers. Nasa is using the D-Wave computer in their Quantum Artificial Intelligence Laboratory (yes, such a place really exists).
Another challenge is how to develop useful quantum algorithms for quantum processors. This is a difficult task because the architecture of quantum processors differ from classical processors. In brief, whereas digital computers use binary digits (bits), each of which is always in one of two definite states (0 or 1), quantum processors use qubits, which can be in superpositions of states (that is 0 and 1 simultaneously). This fundamental architectural difference is what makes the quantum computer so efficient. A large-scale quantum computer will solve certain problems much faster than any classical computer. Here too we are seeing progress and many quantum algorithms have already been developed. Famous examples are Shor's algorithm for integer factorization and Grover's algorithm for unstructured database searches.
We'll also need practical tools for using and programming a quantum computer. In practice this means programming tools, interfaces, and compilers that enable us to run quantum algorithms on quantum processors in a meaningful way. We've done the same in classical computing where we today seldom write programs in machine code like Assembler. Instead we use languages of higher abstraction, such as Java and C++, and development tools around those languages. The people who work with Quantum Architectures and Computation at Microsoft Research summarize this well: we need Visual Studio for quantum computing.
We can Expect Breakthroughs Soon
Given the timeline of quantum computing development and the fact that more and more resources are poured into this, it seems likely that we'll make significant breakthroughs in the foreseeable future. In December 2015 Google announced that it had proved that the D-Wave computer really works. At the same time Google is also developing their own quantum computer and IBM and Microsoft have substantial quantum computing projects.
It will however take a long time before we have quantum computers in our homes, not to mention in our pockets. A practical reason for this is that in order to prevent quantum decoherence the core components must be cooled down close to absolute zero (0.015 Kelvin in D-Wave’s case). But one could argue that precisely like no-one has a supercomputer or massive storage capacity in their homes today but instead available in the cloud, the same could apply for quantum computing. In a sense, using the quantum (cloud) processor would be like using a math co-processor. In D-Wave System's vision the cloud quantum computer would be called upon when needed for certain types of operations and thus complement classical computing.
Implications for the Future
If all of this becomes reality, what are the practical implications? Or rather, how dramatic will the impact be on our future development? What exactly are the dangers involved? This is of course where things get more speculative, and even philosophical to some degree. Needless to say that there are are a lot of different opinions and conflicting views.
It seems however certain that we will achieve a dramatic speedup in many optimization problems. Tasks that would require millions of years of processing by classical computers could be solved in minutes by quantum computers. This would be of great value to science and technology. We could run simulations that are impossible to conduct today. For example, modern chemistry and nanotechnology rely on understanding quantum systems, but such systems are in practice impossible to simulate classically. Quantum simulation could be the key for making important breakthroughs in these fields.
There are many other areas that would also benefit from quantum computing. Machine learning, which is central to artificial intelligence research, is a good example. The reason is that machine learning relies on learning from and making predictions on data. Quantum database searches (e.g. using Grover's algorithm) offer a significant speedup compared to classical computing. Cryptography would also be raised to a new level, since the methods we use today (e.g. RSA on the Internet) would be useless because factorization is trivial for a quantum computer.
The dangers arise from the fact that all new powerful technologies can be misused, either intentionally or unintentionally. It could be utilized for developing new forms of attacks in the ongoing cyber arms race. Or we could accidentally stumble into something in scientific research that unleashes hell on earth. I don't want to put too much emphasis on the dangers, because I'm optimistic and convinced that the benefits far outweigh the potential problems.
Quantum computing is also very interesting from an economical viewpoint. It may in fact be exactly what we need in order to raise knowledge and information (and ultimately productivity and resource utilization) to a totally new level. The benefits to our environment and our standard of living could be immense. It goes without saying that all investors should keep their eyes on developments within this field. I'll probably come back to this interesting viewpoint in another blog post.
Niels Bohr said that prediction is very difficult, especially if it's about the future. Nevertheless I predict that what I've described in the previous paragraphs will most likely become reality during my lifetime. The thought of this gives me hope and joy amidst all the depressing news we see daily.