(Microsoft) Quantum computing offers the promise of solutions to previously unsolvable problems, but in order to deliver on this promise, it will be necessary to preserve and manipulate information that is contained in the most delicate of resources: highly entangled quantum states. One thing that makes this so challenging is that quantum devices must be ensconced in an extreme environment in order to preserve quantum information, but signals must be sent to each qubit in order to manipulate this information—requiring, in essence, an information superhighway into this extreme environment. Microsoft’s David Reilly, leading a team of Microsoft and University of Sydney researchers, has developed a novel approach to the latter problem. Rather than employing a rack of room-temperature electronics to generate voltage pulses to control qubits in a special-purpose refrigerator whose base temperature is 20 times colder than interstellar space, they invented a control chip, dubbed Gooseberry, that sits next to the quantum device and operates in the extreme conditions prevalent at the base of the fridge. They’ve also developed a general-purpose cryo-compute core that operates at the slightly warmer temperatures comparable to that of interstellar space, which can be achieved by immersion in liquid Helium. This core performs the classical computations needed to determine the instructions that are sent to Gooseberry which, in turn, feeds voltage pulses to the qubits. These novel classical computing technologies solve the I/O nightmares associated with controlling thousands of qubits.
Microsoft Quantum researchers are playing the long game, using a wholistic approach to aim for quantum computers at the larger scale needed for applications with real impact. Aiming for this bigger goal takes time, forethought, and a commitment to looking toward the future. In that context, the challenge of controlling large numbers of qubits looms large, even though quantum computing devices with thousands of qubits are still years in the future.
They’ve also extended this research to create the first-of-its-kind general-purpose cryo-compute core, one step up the quantum stack. This operates at around 2 Kelvin (K), a temperature that can be reached by immersing it in liquid Helium. Although this is still very cold, it is 20 times warmer than the temperatures at which Gooseberry operates and, therefore, 400 times as much cooling power is available.