INTERVIEW WITH DR. STEPHANIE SIMMONS

Department of Physics (Silicon Quantum Computing)

Joined SFU in October 2015

With a goal of developing quantum technologies, Dr. Simmons’ work falls squarely between engineering and physics. She believes that silicon is the way to go for quantum computing because “thanks to the hugely successful semiconductor industry, we really understand how to make accurate, reliable nanoscale structures in silicon.” Control and accuracy are essential to realizing the potential of quantum technology and bringing it into the mainstream.

What early life experiences influenced you to pursue a career in science?
I was part of that first generation of kids who grew up with 286 and 386 computers and was fortunate to have one at home. I remember the awe of programming a computer to do stuff, and early video games were so interesting – that's what captured my interest in subjects like math and science.

What was it about a computer that got you so hooked?
I remember playing with that giant box and the joy I experienced, especially when I could fix something that my parents couldn't. My generation was probably the first to have computer skills be such a major part of their early identity.

What part of your quantum technology research gives you the most satisfaction?
My research is very goal oriented, which is different from researchers who are explorers. I want to develop next-generation technologies, and to make that happen, you end up doing a lot of basic science.

The main challenge is figuring out how to control quantum systems – we want them to bend to our will, but it’s not obvious how to do that. It's fantastic to finally click and put the pieces together, to take a small step forward to a breakthrough. Now as a Prof, I can put my trainees into a situation where they too can have these eureka moments.

What do you think about the Canadian government’s focus on applied rather than fundamental research?
Although this focus makes it a great time to get funding for my program, it is short-sighted. We need basic science. The research that I'm doing could not proceed had it not been for scientists who dedicated their careers to studying the basic science behind it. If we don't promote fundamental research now, then future generations will have a limited basis for innovation.

Do you worry about spending years pursuing one approach to quantum computing, only to realize that it was the wrong way to go?
My field is certainly prone to this. But you wouldn't do it unless you were absolutely convinced that you have the solution. This work is high risk with a big reward.

My research program has a safety net in the sense that any developments in silicon are going to have all kinds of spin-off effects, even if they don't contribute toward the central goal.

In computing, how does the traditional data unit, the binary digit or ‘bit’, compare to a quantum bit?
In a classical computer, the operation would involve flipping a zero to a one; in a quantum processor, it would be flipping between individual quantum states [of which there are more than just 0 or 1] and those operations are more complex.

The quantum states of quantum bits or ‘qubits’ have certain lifetimes. What lifetime is needed before a quantum computing technology becomes practical?
What matters is how long a qubit’s quantum state can live compared to how long it takes to perform operations. Different qubits require different amounts of time for those operations.

Realistically, you need a lifetime long enough to perform at least a million operations. The problem with quantum technologies is that you require really high accuracies, and short lifetimes have higher error rates. You want the native error rate of the qubit to be as low as possible. Fortunately, our silicon qubits are excellent, with long lifetimes and low native error rates. We even set records for quantum lifetimes here at SFU.

For us, control errors are a bigger problem, but we’re still within limits set by quantum error correction strategies. Eventually, we will have to improve control errors, because the lower the control error, the less redundancy is needed, which is a good thing. The crucial to-do item for us is linking qubits together reliably.

The linking of multiple qubits is a critical requirement for quantum computer function – in practical terms, how do you foresee linking qubits so that they can relay information?
Our long-lived atomic qubits are naturally isolated and therefore don't respond much to changes in the environment. That isolation is at odds with having them communicate with each other.

My approach to enabling qubit communication is different from that of others. Instead of using direct interactions between qubits, I'm going to link qubits through an intermediate quantum object – a photon.

You can engineer a silicon chip so that photons will be really sensitive to the environment only in specific locations. This is called ‘quantum electrodynamics’ – it involves making little pockets where the photons are sensitive to the environment and the rest of the time they are relatively insensitive. They can be routed around on a chip, moving quantum information around and the places where they interact strongly with the environment is where you put one of the atomic qubits. The strong interaction is similar to having two mirrors where the light bounces back and forth a lot in that region.

Essentially, this will set up a hybrid network. It will have huge implications for how we work with on-chip fiber optics – for example, information can be moved around much faster.

You plan to move information between a qubit and a photon and the photon will relay that to other qubits. Does this system have drawbacks?
You need to worry about losing the photon; they always interact with their environment a little bit and a light beam may get dimmer over time because photons get absorbed.

One solution is to use ‘quantum teleportation’, which involves using theory that was developed for other platforms like superconducting qubits and ion traps, but has not been applied successfully to silicon before.

Of all the applications for quantum computing, which one motivates you the most?
The understated application is in health. All of the chemistry, the ways drugs interact with targets and other processes are ultimately dictated by quantum mechanics. Because quantum mechanics cannot be calculated efficiently on classical computers, approximations are made and they fail at a certain point.

Quantum computing will change the world in ways we are unable to predict. In terms of what we know already, the health implications will be huge because it will enable researchers to progress in a direction that has eluded them.

Are there any issues that might arise with the widespread implementation of quantum computing?
A huge issue is information security, because quantum technology has the ability to hack RSA, the cryptographic tool used to secure most online communications. But quantum technology offers the ability to have unhackable cryptography.

Classical cryptography uses computational encryption, which relies upon there being a certain thing that is hard to compute. In the case of RSA, the difficult-to-compute aspect is finding the prime factors of a very large number. It's really hard to do that computationally, but not impossible; if you were given one of the prime factors then it's a lot easier to figure out the others.

In contrast, quantum encryption relies on physical properties of quantum mechanics—for example, it is impossible to copy quantum information. That means it has some really cool information security aspects, it offers the ability to have perfectly secure communications.

When will we see mainstream quantum computer applications?
Most quantum applications will arise when we get to the point where we have a generation who grew up with quantum computing. Those 5-year-old kids who will have a 200-qubit quantum processor in their home will come up with the bigger changes because they will have a more intuitive sense of how these things work.

What educational background and personal strengths do you look for in prospective group members?
One of the beauties of experimental physics is its collaborative nature with a strong team focus. My work requires a range of skills, so I’m hiring physicists, electrical engineers and computer scientists to start, and eventually perhaps chemists. I am also looking for people who are keen to undertake big risks with big payoffs in this highly competitive field.

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Read more: Dr. Simmons’ Department of Physics website, her Silicon Quantum Technology Lab’s website, a talk by Dr. Simmons on the “Race for a Quantum Computer” and back to the New Science Faculty page

Interview by Jacqueline Watson with Theresa Kitos