Quantum computing is one of those terms that many of us have heard, but not many actually understand. There's been plenty of buzz around quantum technologies recently and investments in the space are at an all-time high—around $177 million, according to analyst estimates. That number is forecast to skyrocket to $15 billion US by 2028.

So why all the excitement? And what is quantum computing exactly? Are we just talking about faster processing and better storage? Dr. Irfan Siddiqi, a professor of physics at the Quantum Nanoscience Laboratory and the Department of Physics at the University of California Berkeley, says that quantum technologies represent a whole new way of thinking about computing.

Dr. Irfan Siddiqi |

Ahead of his keynote at DesignCon 2019, Siddiqi spoke with *Design News* to separate the facts from hype of quantum computing, where the technology is today, and the impact it could have in the future.*

**Design News: Let's start at the beginning. What's your definition of quantum computing?**

**Irfan Siddiqi: **For me, any quantum technology, including quantum computing, is something that takes advantage of entanglement. And entanglement is the idea that if you have different pieces of matter and you put them together, they behave as a single unit.

So, for example, each of the bits in a classical computer are independent of each other. If you flip one, it doesn't affect the one next to it. In a quantum computer, all of these bits have correlations with each other, so they're all tied together like one big mass. In fact, the number of states that they can occupy is exponentially larger because of these linkages between neighboring elements.

Quantum computing is the science of manipulating this entangled set of bits for some particular problem of interest in either fundamental science and computation or to do a simulation of the natural world.

**DN: So are speed and processing power the only advantages here? Or are we looking at other things as well?**

**IS**: I would say it will actually be a bit deeper than that, although those terms are correct. The power behind quantum is that it changes the types of problems you can solve. So it's not as if it goes a little bit faster than your classical machine. It will take those problems that are impossible on a classical machine and make them possible in real time. And the reason for that is the structure that quantum machines have, where information is stored in such an exponentially larger capacity. It allows you to process things in very different ways. And not only are they faster; They're just really different problems. Problems that are intractable in the classical domain become pliable using quantum devices.

**DN: What sorts of problems are those?**

**IS**: The one that is usually given for general computing is factoring a number into its prime factors. This is the hallmark example of quantum computing. Shor's Algorithm is the one that's used to factor a number into its primes. This is the modality of security that is most often used. The ability of classical computers to multiply numbers, but their complete inability to factorize them, is what is the basis of many security algorithms.

But quantum computers can do that very readily. So that's a very good cryptographic, cryptology, communication kind of example.

More on the scientific domain: If we look at even the structure of chemical molecules, even though the theory of quantum mechanics told us about 100 years ago how to solve for their energy structures, we are unable to do this for something beyond an order of about 10 atoms.

So that's kind of shocking—that even with the best computers, you can't solve something more than 10 atoms. There are many, many, many atoms that make up even the simplest of molecules. By using quantum devices, we would be able to, in principle, understand the chemical structure dynamics of things much larger than that number and that could have very profound consequences for artificial solar cells, new types of fertilizers, new types of catalysts—all sorts of things in materials science that, at the moment, are really unreachable to us using classical computations.

**DN: So with that, how feasible is it to actually build a quantum computer?**

**IS**: What is involved in building a quantum machine is that we will have to extend the size of our computer bit by bit.

So this sounds a bit strange because we're used to having trillions of transistors in even the simplest of computers. Even your watch probably has many more transistors than that. Nonetheless, one has to sort of go back a bit to the day of vacuum tube computers and even before that, where literally we were putting together computing architectures bit by bit, transistor by transistor. This is the state that we're in with quantum devices.

So it starts off by taking a physical system that exhibits quantum mechanics. At the moment, we have a very preferred physical system for classical computers. This is silicon technology, and we use it to make transistors and so forth. We have not arrived at the one magical technology platform that can be readily used to build a quantum computer. We're still surveying the field and all the sorts of different technologies that could build these devices.

One example would be to use individual atoms or ions, so you literally put a computer together one atom at a time. This would be called an ion-based quantum computer.

We are taking a different approach [at Berkeley]. We use electrical circuits. They are made of metals and each circuit is a resident circuit like an oscillator or a pendulum. Each one of these electrical oscillators is a qubit [quantum bit]. We build these out of superconducting metals, so if we put them to very low temperatures, there's no resistance. It's the resistance that causes the pendulum to slow down. The idea here is that you would build an oscillating circuit that doesn't stop for very many oscillations and allows information to be stored without being lost.

That's one quantum bit built out of electrical circuits using superconducting metals. The goal is to put many of these circuits together and entangle them and build a quantum machine. So the state of the art right now is somewhere between 10 and 100 of these qubits for any modality, whether it's ions or superconductors or what have you.

**DN: Is just 10 or 100 qubits enough for any realistic application?**

**IS:** I would say, in the industrial or commercial domain, we have no quantum machine that can outperform a classic one at the moment. This is called quantum supremacy or quantum ascendancy. There's a race to build a machine that can outperform a classical counter.

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