Thursday, June 03, 2021

Quantum computing on Youtube

I recently watched two videos of interest regarding quantum computing.

As you might expect, Google is going into it in a big way, and while the comedy in this does not really work, it's still interesting:

And Bee Hossenfelder had an informative video on the various approaches to creating quantum computing. I didn't realise there were so many: 

Update:   I have been meaning to say, since I first posted a photo of these early quantum computer set ups, that I like the lacy, intricate design of the Google quantum computer, which is all about the need for extreme cooling. Which has made me wonder - how do you cool something down to below the temperature of space? This article gives some indication, although I still don't understand exactly how it works: 

 “Quantum chips have to operate at very low temperatures in order to maintain the quantum information,” Clarke said. To do this, Intel uses cryogen-free dilution refrigerator systems from specialist Blufors.

The refrigerator features several stages, getting colder as you go down - all the way "down to temperatures just a fraction of a degree above absolute zero - that is really cold. In fact, it's 250 times colder than deep space,” Clarke said. “We use a mixture of helium isotopes as our refrigerant to get down to these very cold temperatures, in the tens of millikelvin.”

While the refrigeration system can bring temperatures down to extremes, it can't remove heat very quickly - so if you have a chip in there that's creating a lot of heat, you're going to have a problem.

"You're probably familiar with the power dissipation of an FPGA," Clarke said. "This would overwhelm the refrigeration cooling capacity. At the lowest level of a fridge, you typically have about a milliwatt of cooling power. At the four Kelvin stage [higher up in the fridge], you have a few watts."

Future fridge designs are expected to improve things, but it's unlikely to massively increase the temperature envelope. "That imposes limitations on the power dissipation of your control chips."

 

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