Remote Quantum Computing Is the Future

A personal take on science and society World view By Christopher Monroe Remote quantum computing is the future

Conditions created by the COVID-19 shutdown EURIQA (Error-corrected Universal Reconfigurable Ion are delivering one experiment’s ‘best data ever’. trap Quantum Archetype) began operating autonomously It would be in April 2019. The whole system now sits in a 1-metre-cubed box. It’s rarely opened. One researcher visits the lab for he COVID-19 pandemic and shutdown have been great if some 10–20 minutes once a week to reboot the odd computer disastrous for many people. But one research quantum that has frozen or power supply that has tripped. project in my lab has been humming along, tak- components Since my university went into COVID-19 shutdown in ing the best data my team has ever seen. It is an March, EURIQA has kept running — all day, every day. And advanced ‘ion trap’ quantum computer, which were ‘plug- the data have been excellent because the campus has been Tuses laser beams to control an array of floating atoms. and-play’, a ghost town. The lab’s temperature hasn’t wavered and We spent three years setting it up to run remotely and like the flash there’s little vibrational noise in the unoccupied build- autonomously. Now, we think more labs should run quan- ing. It’s one of very few university quantum experiments tum-computing experiments like this, to speed up research. memory on a making real progress right now. Quantum computers exploit the weird behaviour of mat- smartphone But there’s a bigger picture. This remote mode of ter at the atomic level. One particle can store many pieces of camera.” operation is exactly what’s needed in quantum-comput- information, allowing the computers, in effect, to perform ing research. Companies including IBM, Google, Honey- many calculations simultaneously. They promise to solve well and a start-up I co-founded, IonQ (whose systems are problems that are out of reach of conventional machines, based on EURIQA), are opening up commercial access to and to speed up modelling of chemical reactions in bat- their early quantum-computing devices. By the end of teries or drug design, or even simulations of information 2020, several types of quantum computer will be available flow in black holes. through cloud services hosted by Amazon and Microsoft. But good quantum hardware is extremely fragile, and But researchers won’t have access to the inner workings to the larger the system, the more easily it is perturbed. Some advance bespoke designs for particular scientific applica- quantum components must be chilled to near absolute tions. They won’t be able to ‘co-design’, or fully exploit the zero. Others must be stored in a vacuum more rarefied interplay between computer fabrication and computer use. than that of outer space. It’s really hard to prepare and Right now, most quantum-computing research involves control precise quantum states, let alone keep them sta- the study of qubit properties, quantum gate operations ble for hours. Stray currents, changes in temperature and and their control. In some cases, the components are wired vibrations can easily destabilize the system. together for a specific scientific application. Qubits, quan- The quantum computer at the University of Maryland, tum logic operations and modes for executing programs led by myself and physicist Marko Cetina, uses up to 32 iden- are selected and optimized for one purpose. It would be tical atoms as the quantum bits, or qubits. Each is levitated great if instead, some of those components were simple by electromagnetic fields and cooled by lasers to sit almost ‘plug-and-play’ commodities, like the flash memory on a at rest. Typically, such an apparatus has thousands of elec- smartphone camera. Then, researchers wouldn’t have to tronic and optical components, all aligned precisely on a build everything from scratch: they could insert a module, 3-metre wide, 500-kilogram steel table damped against tweak a parameter or remotely reprogram a circuit. vibrations. It requires an army of people to tweak mirrors Such a system could be built by adapting a particular and adjust signals, and the components must continually qubit technology and piling stacks of control hardware be replaced, tested, calibrated and updated. and software on top, as we have done with EURIQA. Qubits But in 2016,we decided to redesign our system to run Christopher Monroe could be swapped and systems redesigned as technology remotely — not just for convenience, but because that’s is a physicist evolves — just as in conventional computing, the vacu- what our research goals require. We needed to add more and engineer at um-tube switches of the 1940s gave way to germanium qubits without increasing noise and errors, to test complex the University of semiconductors and then silicon wafers in the 1960s. quantum gate operations, circuits and algorithms. Maryland in College Large quantum-computing initiatives in the United This required a different approach. For qubits, we use Park and at Duke States, Europe, China, Canada, Australia, Singapore and particular states of ytterbium-171 that are so stable that University in Durham, Russia are investing in qubit research while also giving they are widely used for atomic clocks. We miniaturized the North Carolina. He researchers access to commercial cloud services. But most reliable control components, added transducers and is also co-founder extensive research is needed between these extremes. feedback circuits, and ran everything from an open-access and chief scientist at Industry will ultimately mass-produce quantum comput- software platform. We worked closely with many industry IonQ. ers, but the early ‘killer apps’ might well come from scien- partners to make it all work, in a collaboration with engi- e-mail: monroe@ tific discovery. Unleashing ‘full stack’ quantum computers

CHRISTOPHER MONROE CHRISTOPHER neers Jungsang Kim and Kenneth Brown at Duke University. umd.edu into the research community will hasten that search.