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Interview: Gary Steele

Hi Gary! We're here at the ScaleQIT International Conference 2016 in Delft, Netherlands, a showcase for the latest research on quantum information technologies that was held in late January this 2016. What's the cool thing about exploiting quantum phenomena to tackle technological problems?

Well in our case you could say we're more taking advantage of quantum technology to do some interesting physics!

For your experiments you couple nanomechanical resonators with high-quality superconducting microwave resonators. What interesting effects result from this marriage?

We use superconducting devices to detect the motion of vibrating objects with very high precision and ultimately measure them in their quantum ground state. From there you can go on and program arbitrary quantum superposition states. Nobody has looked at these quantum states of motion; it's sort of an uncharted territory!

Another possibility is to use these vibrating objects as sensors. An example is the atomic force microscope which uses a mechanical cantilever to measure van der Waals forces between tip and surface. With functionalized tips you can go on and use that same AFM to measure electric or magnetic fields. If you have precise sensor for forces you can easily get precise sensors for many more physical phenomena.

So this seems to be the place where these devices are going to be applied. On what timescale do you think this will happen?

Difficult to say, in fact in our field we rather focus on something else: using nanomechanical systems to transduce microwave photons into optical photons. That's attractive because it's easier to transmit optical photons over long distances. There's been impressive progress lately and this transformation has been demonstrated. Based on that you can envision entangling qubits with microwave photons, convert them to optical photons, and send them down the fiber!

Through the quantum internet!

... and via satellite to Japan!

You use the HF2LI 50 MHz lock-in amplifier for your measurements. Which features help you?

We use the HF2LI to perform high-speed measurements of carbon resonators (Appl. Phys. Lett. 107, 053121 [2013]), recently observing decoherence in the motion of a vibrational nanotube (Nature Comm. 5, 5819 [2014]). You can do these measurements with analog mixers, and we tried. But the non-ideal mixers essentially make your signal "explode" into a mess of sidebands. With the HF2 you can do all the filtering and mixing in the digital domain where things are much closer to ideality. And that made the difference between spending half a year getting the analog setup to work, and just plugging in the HF2LI and start measuring. The other useful thing is the low time constant down to 800 ns, which allowed us to do very fast ring-down measurements.

Tell us something you love about Dutch weather.

It's miserable much of the time, but the misery makes you appreciate the good weather more. So, if there's a sunny day, you have a smile on your face and a happy warm feeling even if it's cold outside!

Gary Steele

Gary Steele (Researchgate) heads up the Steele Lab in the MED group Department of Quantum Nanoscience, Kavli Institute of Nanoscience at the Delft University of Technology.

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