Tuesday, February 3, 2015

Solar and Smart Grids

I recently realized something about solar power and smart electrical grids and I feel sort of stupid for not realizing it earlier.  But rather than stew in shame I should probably share it with all of you since I expect most of my readers, not having had the benefit of working at Ember, have no idea what a smart grid is.

But first, solar power.  For a while now the prices of solar cells has been plummeting.  Not with the outstanding reliability of Moore's law but at a fearsome rate nonetheless.  Which is really awesome in terms of reducing carbon use!  But there's a problem.  Solar energy only works when the sun is shining.  At night, there's no solar energy at all so you need to run some other sort of electrical generation to keep things running.  You still have to build enough non-solar infrastructure that you can keep things going even at night.

But there's an even worse problem.  It can take up to an hour to spin up a conventional power plant to the point where it can start generating useful grid power.  That's fine for the nice, predictable fall of night but what about when a cloud passes in front of the sun?  Falling solar prices mean we want to start building more and more solar generation capacity but if it all goes away suddenly that becomes a bigger and bigger problem.

That's where smart grids come in.  We can't change how much energy we produce from minute to minute, but it's a lot easier to change how much energy we use from minute to minute.  The lights have to stay on but you can hold off running a compression cycle on your refrigerator for another 5 minutes.  Or if there's a lot of excess power just go ahead and run it early.  And you can do the same with air conditioning, recharging batteries, many industrial process, etc.  I'd thought that smart grids were a sort of nifty efficiency but I'm coming to view them more as a critical tool in making the widespread use of solar possible feasible.

Monday, February 2, 2015

Quantum teleportation

I recentlyish finished Scott Aaronson's Quantum Computing Since Democritus.  I enjoyed it quite a bit and it managed to explain some things very well.  One of those things was Quantum teleportation - something I've seen mentioned in the popular science press time and again but which always seems to be conveyed very badly.

Before I get to that explanation, though, I'm going to have to explain two things first: qubits and the no-cloning theorem.  Qubits or Quantum bits are the quantum version of classical bits.  Imagine that if a regular bit is an arrow that can point to the left or to the right to represent 1 or 0 a qubit is an arrow that can point in any direction.  That's totally misleading in all sorts of ways but it will work well enough for the rest of this post.  I'm here to explain quantum teleportation after all.

If you have a regular bit you can do a lot of things with it.  For instance you can copy it.  This very blog post, composed of classical bits, has been copied to your web browser dear reader and from there into your very head.  That's a very nice thing about classical bits but sadly you can't do that with quantum bits.  And qubits are fragile things when exposed to the world, prone to collapse or decoherence (depending on your religion).  You can spread one between multiple locations (via entanglement) but you've got to keep it isolated in each place or the whole thing is lost.

But what if I want to share my qubut with my friend across town?  However you try to send it you have to worry about stray atoms or photons ruining the process.  With classical bits you have sends zillions of electrons for one bit and try again if that doesn't work but the non-copyability of qubits prevents that here.  Unless you have a nice isolated fiber-optic cable or something you're out of luck.

That's where quantum teleportation comes in!  If I have a qubit that's in my house and I want to get it to my buddies house I need a couple of things.  I need to send my buddy a couple of bits of classical information but I can do that over the internet or something.  Also you need a second cubit which is already shared between the two places.  Why are you trying to send this first qubit if you're already sharing a second qubit?  Maybe the first one is really awesome and you need it over there now but the second qubit is just some Joe Schmoe qubit that you put in place a month ago.  But in any event you can spend that shared qubit and that nice easy classical information transfer to send your qubit over to your buddy.  So your qubit can teleport from your house to your buddies without ever having to brave the dangerous outside world.

Rockets VII: Staging

See also parts  I ,   II ,  III ,  IV ,  V , and  VI . Space is sort of hard to get to.  You've got one of the Space Shuttle Main Engi...