Controlling up to thousands of qubits at cryogenic temperatures

Quantum stack diagram. Topological qubits sit at the bottom of the stack in the quantum plane along with other electronics needed to help with the processing of information from raw qubits. The Gooseberry chip sits very near the qubits, while Alta is positioned at the bottom of the “Classical Compute” portion of the stack, where it is in communication with both Gooseberry and components higher up the stack. Credit: Microsoft

A team of Microsoft and University of Sydney researchers has developed a novel approach for controlling qubits. Rather than employing a rack of room-temperature electronics to generate voltage pulses to control qubits in a special-purpose refrigerator, 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.

The team has used specialized CMOS circuits to take digital inputs and generate many parallel qubit control signals—allowing scaled-up support for thousands of qubits—a leap ahead from previous technology. The chip powering this platform, the so-called Gooseberry, resolves several issues with I/O in quantum computers by operating at 100 mK while dissipating sufficiently low power so that it does not exceed the cooling power of a standard commercially-available research refrigerator at these temperatures. This sidesteps the otherwise insurmountable challenge of running thousands of wires into a fridge.

These novel classical computing technologies solve the I/O nightmares associated with controlling thousands of qubits. (TechXplore)

The paper has been published in Nature Electronics.

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