A quantum computer is like an orchestra that can only perform in complete silence. The slightest noise, and the delicate melody falls apart. For quantum devices, heat is that noise: even faint infrared radiation from nearby components heats up the qubits and erases their quantum states. What’s needed is a filter that lets control signals through but muffles thermal rays.
Researchers have proposed a material made of epoxy resin mixed with tiny sapphire beads. They tuned the bead size so that infrared waves entering the resin scatter off the beads, like car headlights in thick fog. Meanwhile, the radio waves that control the qubits pass through the filter with almost no loss, like sound through a thin wall.
They tested the filter at temperatures just a few thousandths of a degree above absolute zero. It let signals up to 10 gigahertz through with a loss of less than 0.4 decibels, as if only one photon out of a hundred were lost. And it attenuated infrared radiation just as effectively as conventional metal filters. This material is easier to manufacture and cheaper, bringing quantum devices a step closer to everyday use.
A temperature of a few millikelvin is a hundred times colder than the darkest reaches of space.