Measuring Up: Coming Out from the Cold

The photo shows green commercial circuit boards – the largest is 11.4 cm (4.5 in) by 19 cm (7.5  in) – inside a dilution refrigerator. When enclosed and pumped down, the system reaches temperatures only a few thousandths of a degree above absolute zero.

Credit: NIST

Researchers at the National Institute of Standards and Technology (NIST) have constructed and tested a system that allows commercial electronic components – such as microprocessors on circuit boards – to operate in close proximity with ultra-cold devices employed in quantum information processing. That design allows four times as much data to be output for the same number of connected wires.

In the rising excitement about quantum computing, it can be easy to overlook the physical fact that the data produced by manipulation of quantum bits (qubits) at cryogenic temperatures a few thousandths of a degree above absolute zero still has to be initiated, read-out, and stored using conventional electronics, which presently work only at room temperature, several meters away from the qubits. This separation has obstructed development of quantum computing devices that outperform their classical counterparts.

That extra distance between the quantum computing elements and the external electronics requires extra time for signals to travel, which also causes signals to degrade. In addition, each (comparatively very hot) wire needed to connect the electronics to the cryogenic components adds heat, making it hard to maintain the ultracold temperature required for the quantum devices to work.

“If you consider our modern computers, what practically limits their speed is the time it takes information to move around between the CPU and graphics and memory – the physical distances, even though it is moving at the speed of light!” said the project scientist, Joshua Pomeroy. “Those finite distances kill the performance speed. Everything has to be as close as possi ..

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