The research of Professor Joseph Bardin of the Electrical and Computer Engineering Department is one of three projects featured in an IEEE Spectrum article, titled “Three Frosty Innovations for Better Quantum Computers,” which examines the potential benefits of cryogenically freezing quantum computers. IEEE Spectrum is the flagship magazine and website of the Institute of Electrical and Electronics Engineers. Bardin collaborated with a team of researchers at Google that developed a cryogenic integrated circuit for controlling the heat in qubits, the driving force in quantum computers, and connecting them with other electronics.
Bardin’s Google collaboration is aimed ultimately at building much smaller, more efficient, more economical quantum computers with greater capacities.
As author Rahul Rao explains in his IEEE Spectrum article, “Heat creates error in the qubits that make a quantum computer tick, scuttling the operations the computer is carrying out. So quantum computers need to be kept very cold, just a tad above absolute zero.”
Rao goes on to explains that to operate a computer you need to interface with the non-quantum world. “Today, that means a lot of bulky backend electronics that sit at room temperature,” writes Rao. “To make better quantum computers, scientists and engineers are looking to bring more of those electronics into the dilution refrigerator that houses the qubits themselves.”
Bardin’s Google research was one of three examples used by Rao to demonstrate this kind of pioneering work.
In describing his Google device, Bardin says that “This cryo-CMOS circuit isn’t much different from its room-temperature counterparts. But designing it isn’t so straightforward. Existing simulations and models of components aren’t tailored for cryogenic operation. Much of the researchers’ challenge comes in adapting those models for cold temperatures.”
Google’s device operates at four kelvins inside the refrigerator, just slightly warmer than the qubits that are about 50 centimeters away. That frigid setup could drastically shrink what are now room-sized racks of electronics.
As Bardin observes in the IEEE Spectrum article, this cryo-IC approach “could also eventually bring the cost of the control electronics way down.” Efficiently controlling quantum computers, he says, is crucial as they reach 100 qubits or more.
Bardin heads the UMass Quantum RF Research Group. As he says about his lab, “We perform basic research on CMOS and BiCMOS integrated electronics to control and measure quantum devices such as qubits, single photon detectors, and THz mixers. A common theme is that our devices are optimized to work at very low temperatures, often in the range of four to 20 degrees above absolute zero.” (March 2021)