First stop was the lab belonging to Chris Monroe, where he and his team are developing quantum qubits, the fundamentals of future quantum computer processors. Modern computer processors are vast farms of microscopic switches known as transistors made out of a semiconductor material like silicon. A computer uses binary code, long strings of ones and zeroes, to flip these tiny transistors into on or off positions. With properly programmed algorithms, the processor can solve problems and the more transistors in the processor, the faster it is.
Introducing quantum qubits into computing would change everything. Instead of transistors only able to be either on or off, qubits can be in a quantum superposition, both on and off simultaneously, which would exponentially increase the computer’s processing power.
However building a quantum dot processor is difficult because the tools to manipulate and position the dots still aren’t really precise enough to build a robust system. Waks is working on improving the precision of optical tweezers which he uses to move quantum dots around the clover-shaped fluid passages on a postage stamp sized slide.
Using green lasers, he can nudge the tiny quantum dots suspended in the fluid and precisely move them around at a rate of about two micrometers per second. The system he developed is a lot more precise than most other methods, and a version could be used in the future to position quantum dots on silicon chips in some future quantum processor.
The last lab was Gretchen Campbell whose work is exploring the more fundamental aspects of quantum particles. She specializes in creating and exploring Bose-Einstein condensates, a truly weird quantum state of matter. For dilute gases at temperatures just a fraction of a degree above absolute zero, the particles’ superpositions start to spread out and overlap and with each other, making and the whole macroscopic gas act like a quantum system.
Most of this apparatus is essentially a refrigerator to cool strontium atoms into the near-zero temperatures needed to create a BEC. The process starts with a strontium sample placed inside of an induction oven on the far right of the device. Beneath thick layers of insulation, white-hot induction coils burn off strontium atoms from the sample, which bolt along the length of the device.
The heated strontium atoms start shooting down this gray cylinder, called a Zeeman slower at hundreds of meters a second. Lasers and magnetic fields strip most of the energy out of the speeding atoms until they leave the far end of the slower with a fraction of their original energy.
The last step of the process is in the vacuum chamber at the far end of the slower. Here a series of optical traps sap the atoms of nearly all of the rest of their energy, and bring them down to their ground quantum states where they coalesce into Bose Einstein Condensates. The whole process takes less than two seconds.
Once the atoms are in their ground states, Campbell and her researchers can study the properties of the BEC they created. However, unlike Monroe and Wak’s labs, there’s no clear plan for what Campbell’s team is looking to build. It’s research just to understand how this unusual state of matter behaves. There’s a chance that some of this work it might apply to building new sensors or creating new superconductors, but really there’s no way to know what this kind of knowledge might be used for.
Research like this is a big reason that the government created the Joint Quantum Institute in 2006; It’s hard to get companies to sponsor research with no obvious commercial applications. Quantum information has the potential to revolutionize computing, but likely only after many years and billions of dollars of investment. The JQI sponsored by NIST and the University of Maryland, is filling in this research gap and helping to lay the groundwork for future discoveries that could make today’s microprocessors obsolete.