Quantum computing is going to change the world. Here’s what …

The science and tech world has been abuzz about quantum computers for years, but the devices are not yet affecting our daily lives. Quantum systems could seamlessly encrypt data, help us make sense of the huge amount of data weve already collected, and solve complex problems that even the most powerful supercomputers cannot such as medical diagnostics and weather prediction.

That nebulous quantum future became one step closer this November, when top-tier journal Nature published two papers that showed some of the most advanced quantum systems yet.

If you still dont understand what a quantum computer is, what it does, or what it could do for you, never fear. Futurism recently spoke with Mikhail Lukin, a physics professor at Harvard University and the senior author ofone of those papers, about the current state of quantum computing, when we might have quantum technology on our phones or our desks, and what it will take for that to happen.

This interview has been slightly edited for clarity and brevity.


Mikhail Lukin: Lets start with how classical computers work. In classical computers, you formulate any problem you want to solve in the form of some input, which is basically a stream of 0s and 1s. When you want to do some calculation, you basically create a certain set of rules depending on how this stream should actually move. Thats the process of calculation addition, multiplication, whatever.



This means that if I then take this superposition state and process it using the laws of quantum mechanics, I can process many, many inputs at once. It could be potentially an exponential speedup, compared to the classical programs.

F: What does a quantum computer look like?


F: So how do you program the thing?


Positioning these atoms is one way that we can program it. To actually control the qubit, we gently, carefully, push the atoms from their lowest energy state into a higher energy state. We do this with carefully chosen laser beams that shoot to one specific transition. Their frequency is very tightly controlled. In this excited state the atom actually becomes very big and, because of this atom size, the atoms start interacting or in other words talking to each other. By choosing the state to which we excite the atoms and choosing their arrangements and positions, we can then program the interaction in a highly controllable way.


ML: To be honest, we really dont know the answer. Its generally believed that quantum computers will not necessarily help for all computational tasks. But there are problems that are mathematically hard for even the best classical computers. They usually involve some complex problems, such as problems involving complex optimizations in which you try to satisfy a number of contradictory constraints.


Another very well-known example is factoring. If you have a small number, like 15, its clear that the factors are 3 and 5, but this is the kind of problem that very quickly becomes complicated as the number grows. If you have a large number that is a product of two large factors, classically there is pretty much no better way to find what these factors are than just trying numbers from one, two, three, and so on. But it turns out that a quantum algorithm exists, called Shors algorithm, that can find the factors exponentially faster than the best known classical algorithms. If you can do something exponentially faster than using the alternative approach, then its a big gain.



In fact, one significance of our papers [published in Nature] is that we have already built machines, which are large enough, and complex enough, and quantum enough to do scientific experiments that are very difficult to impossible to do on even the best possible classical computers essentially supercomputers. In our work, we already used our machine to make a scientific discovery, which had not been made up until now in part because its very difficult for classical computers to model these systems. In some ways, we are now crossing the threshold where quantum machines are becoming useful, at least for scientific purposes.

When classical computers were being developed, people had some ideas of which algorithms to run on them. But actually it turned out that when the first computers were built, people were able to start experimenting with them and discovered many more practically efficient, useful algorithms. In other words, thats really when they discovered what these computers can actually be good for.

Thats why Im saying that we really dont know now the tasks for which quantum computers will be particularly useful. The only way to find these tasks is to build large, functional, quantum machines to try these things out. Thats an important goal, and I should say that we are entering this phase now. Were very, very close to a stage when we can start experimenting with quantum algorithms on large scale machines


ML: So first lets talk about how one could quantify quantum machines. It can be done along three different axes. On one axis is the scale how many qubits [a quantum bit, the unit that makes up the basis of quantum computer the way bits do in classical computing] it is. More is better. Another axis is the degree of quantum-ness, that is, how coherent these systems are. So eventually, the way to quantify it is that if you have a certain number of qubits, and you perform some calculations with that, whats the probability that this calculation is error-free?








ML: I think we need to have big enough computers to start really figuring out what they can be used for. We dont know yet what quantum computers are capable of doing, so we dont know their full potential. I think the next challenge is to do that.


Then maybe, some more general applications could be commercialized. In practice quantum computers and classical computers will likely work hand-in-hand. In fact, most likely what would happen is that the majority of the work is done by classical computers, but some elements, the most difficult problems, can be solved by quantum machines.

There is also another field called quantum communication where you can basically transfer quantum states between distant stations. If you use quantum states to send information, you can build communication lines that are completely secure. Moreover, through these so-called quantum networks, sometimes called quantum internet, we should be able to access quantum servers remotely. That way, I can certainly imagine many directions in which quantum computers can enter everyday life, even though you dont carry it in your own pocket.

F: Whats something that you wish more people knew about quantum computers?

ML: Quantum computing and quantum technology have been in the news for some time. We scientists know that its an exciting area. Its really the frontier of the scientific research across many subfields. Over the last five to 10 years, most people assumed that the developments have been very futuristic. They assumed that it will take a long time before we create any useful quantum machines.

I think that this is just not the case. I think we are already entering the new era with tremendous potential for scientific discoveries, which might have wideranging applications for material science, chemistry really anything that involves complex physical systems. But I also feel that very soon we will start discovering what quantum computers can be useful for in a much broader scope, ranging from optimization to artificial intelligence and machine learning. I think these things are around the corner.

We dont yet know what and how quantum computers will do it, but we will find out very soon.

Continued here:
Quantum computing is going to change the world. Here’s what …

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