Helium!!!

There’s a new club night in Birmingham called ‘Helium’:

The DJs sport names such as ‘Diesel’, ‘Vermin’ and ‘Yumbolt’. Now if I were spinnin’ choonz at this club I would have called myself DJ Supersolid, but then again maybe they haven’t been keeping up to date with the latest developments in condensed matter physics.

The club has an ‘elements’ theme in general, with an Oxygen room, a Nitrogen room and a Carbon room. Cute. No Niobium room though, booo…

These things are scaling pretty quickly…

Via Michael Nielsen:

Quantum Computers

From the website:

“Maybe you’ve never heard of Quantum Computers before and are partial to purchasing from another company that might have advertising everywhere you look.”

Ah, shucks… so that’s where I was going wrong.

Fridge surgery

Take a look at this picture:

mwahaha

Yes I am hacksawing a dilution refrigerator….

One of the entry ports to the IVC has been hardsoldered with a stainless steel placeholder bush. We need to replace this with our custom made copper bush with feedthroughs for coaxes and DC lines. It is virtually impossible to remove this part given the small space around it, and we decided that we don’t want to put power tools nearby, lest we accidentally buzz through the dilution unit. Which would be a bit like putting a scalpel through the jugular.

So hacksaw it is.

I wonder how many low temperature physicists have wanted to saw their dilution fridges in half before. Today I got to indulge in that pleasure. The results weren’t pretty at times:

that's gotta hurt

Although half way through I started thinking ‘I hope that this is the right part I’m sawing…’

It’s not cake but it’s close!

Here are some pictures of our Liquid Nitrogen Ice cream endeavours… mmm. Disclaimer: Don’t try this at home unless you have had training in handling cryogenic liquids πŸ™‚

physics and cake

Ingredients: Cream, milk or that strange stuff we don’t have over here, sugar, crushed fruit, and liquid nitrogen. Recipe: Stir the sugar into the cream until it dissolves, then beat it with a whisk until it is light and fluffy. Then add the fruit, mix it in, and then add the LN2, stirring continously until it has hardened. It takes about 5 minutes, as opposed to waiting for it to cool in the freezer for hours. You can use chocolate chips too but for some reason the fruit one seemed to come out better.

physics and cake

Because you have to keep stirring it, it tends to come out in fluffy bits rather than scoopable ice cream, but you can still pack it into a bowl or cone the same way πŸ™‚

physics and cake

Rather tasty too. You have to be careful when you eat it, sometimes you get a REALLY cold bit in the middle and a rather bad Ice Cream Headache
To keep it from melting on a hot summer’s day, just add more LN2 topping:

physics and cake

Quantum computing fail…again.

Courtesy of Quantum Bayesian Networks, an article entitled “The Quantum Leap of Quantum Computing” on Penny Sleuth. It’s great to see a wider business and market audience becoming interested in QC.

However, this is slightly irritating:

“This means computers would become exponentially more powerful because each β€œquantum bit” (qubit) could store a much greater range of numbers than the two that binary math restricts us to. Imagine a laptop with the computing power of the world’s 10 most powerful supercomputers. Then you begin to grasp the potential of quantum computing.”

In the spirit of a very popular television program:

talent_fail

Let me explain for any readers who are slightly confused at this point: Quantum computers will be very good at solving certain types of hard problems somewhat faster than classical computers. This should become some sort of mantra. (If anyone can think of a catchy version that would be cool).

They won’t be general purpose machines. The best way to think of a QC is more like a co-processor (say like a hardware graphics accelerator).

The types of problems that they will be good at solving are exciting and interesting in themselves. Quantum computers are cool enough without the overhype πŸ™‚

Lab tasks which make me wish I was a theorist

It’s not all fun and games in the lab. Here is a list of the top 10 (in my opinion) most boring tasks that need doing in a Low Temperature device laboratory:

10.) Chiselling ice off the cold traps
You have to do this otherwise you can’t get them out. Some cold traps are better than others, the ones I have on my fridge aren’t very good, they get iced up quite often.

9.) Adding exchange gas to the IVC.
I use Hydrogen exchange gas, which allows the innards of the vacuum can to cool by conduction and convection, before the temperature gets low enough to freeze out the Hydrogen (at which point it becomes a pretty good vacuum). However, adding it to the IVC is slightly irritating as you need to connect up a vacuum pump, balloon of Hydrogen, etc.

8.) Calibrating thermometers
Thermometry is a pain. Alas, it is also one of the most important parts of the apparatus, as temperature is a rather important variable in most experiments. Writing software calibrations, entering long tables of values, using generic calibrations if you’ve lost the long tables of values….

7.) Making leak-tight He-4 to vacuum feedthroughs.
Stycast is your friend πŸ™‚ They have to be tested by being dipped into a dewar of helium, via a hollow feedthrough rod to which they are soldered in place at one end, whilst the other end is simultaneously connected to a leak detector.

6.) Winding magnets / making superconducting persistent mode magnets
Spot welding superconducting joints for heat switches and winding/potting/quench training magnets – argh!

5.) Making custom filters
Commercial kit just doesn’t work at low temperatures. I’ve had commercial filters fail a few times, and it’s not an easy bug to fix, especially when they only stop working at liquid helium temperatures…

4.) Soldering coaxial cables/adapters
Luckily I now almost exclusively use CuNi cables, which will accept standard solder. Prior to that, stainless steel was the only real option. Soldering to stainless steel is difficult.

3.) Leak testing apparatus
It isn’t fun but it really does need doing each time you remake an Indium seal (for example). The hassle a leak would give you once the apparatus is cold isn’t really worth the few hours it takes to do a leak test.

2.) Fixing leaks in the apparatus
Whilst leak testing is irritating, fixing a leak is even more so. Especially superleaks (leaks that only occur at Liquid He tempertaure). A world of pain.

1.) Filling the fridges
Yep, it’s the most boring job in the world. It takes hours and needs doing every couple of days depending on how hungry your fridge is feeling. Luckily, closed cycle systems are becoming ever more popular. Here’s to a bright, cryogen free future! πŸ™‚

If people can think of any more I’d be happy to add them to the list…