Saturday, April 16, 2016

Quantum Computing

A reporter tried to trap Justin Trudeau (the dreamy PM of Canada according to Ms. Rabett) by asking if he could explain quantum computing and Trudeau provided a serviceable answer

Eli would like to riff off this in a slightly different way.

Generally speaking there are two types of problem solvers, the sequentialists who grind things out one step and a time.  A normal computer is like that.  

The other style is to build a complex mental model of the problem that allows for a one step solution.  That is quantum computing.

In the world of quantum electrodynamics, Julian Schwinger was the grinder and Richard Feynman the visionary.


david lewis said...

I've never heard anyone explain how a quantum computer would do an actual computation.

Trudeau says

"What quantum states allow for is much more complex information to be encoded into a single bit. Regular computer bit is either a one or a zero, on or off. A quantum state could be much more complex than that, because, as we know, things could be both particle and wave at the same time, and the uncertainty around quantum states allows us to encode more information into a much smaller information. So that's what's exciting about quantum computing,"

All I would ever want to do is store a 1 into one of these quantum bits until I wanted it back. The last thing I want to hear about when programming is uncertainty.

Didn't Feynman say "I think I can safely say that nobody understands quantum mechanics"?

The only thing I understand about quantum mechanics is they cooked it up to explain experimental observations that made no sense, and the theory proved to be good enough to predict even more bizarre things that turned out to be observable.

If someone is going to make a computer exploiting these properties that make no sense, I think they should be able to explain how it could perform an operation.

Aaron said...

If you use gravity to aid you in your daily routine, then you should be able to tell us how gravity works.

Anonymous said...

I've always been a grinder. (Maybe that's why I had such a hard time with Quantum Mechanics and Path Integrals?)

Kevin O'Neill said...

I think quantum computing will be a revolution in programming - but no more so than the move to object-oriented programming. The real revolution will be in the speed of obtaining results.

D-Wave provides some insights into their quantum programming efforts.>

CapitalistImperialistPig said...

I don't buy your characterization of Feynman vs Schwinger. Both were visionaries who were formidable calculators. Feynman was far more charismatic, though.

EliRabett said...

Eli took QM from a student of Schwinger and stands by his characterization. Both were brilliant to be sure, but in very different ways. People underestimate style in science. Learned thermo from Fermi's simple book and adopted that style rather than grinding.

An amusing simile is the difference between programming in LabView or assembler.

Anonymous said...

My nephew is working on a PhD in quantum computing.

Anonymous said...

Implementing object oriented concepts is not particularly difficult in Forth, the reason that it hasn't caught on for really big programs is that one requires millions of programmers that can operate as a team that can actually read and understand the code. The beauty of Forth is that is allows the nearly instantaneously (microseconds) recompilation of the entire operating system and programming language from source code in a fashion the is nearly identical to how life does it from DNA, and can be understood and implemented by a single individual. I guess higher order life nowadays usually requires two individuals. The biggest problem with Forth is the multitude of ways it can be implemented at the assembler and nucleus level.

So when it came time for me to learn how to program, it was vital that I did it in an environment amenable to scientific study and with scientific relevance. Quantum computing will be required simply to beat the 5 nm macroscopic barrier in semiconductor donor acceptor physics. Consider a quantum computer more as a quantum simulator, where it is easier to just simulate the quantum physics using quantum physics than it is to simulate it with a deterministic van Neumann machine. Physically implementing a very large and complex quantum computer is going to require a combination of natural and directed atomic self assembly and active machining of the resulting structures to tailor them to a specific task. These are neural networks implemented in solid state and condensed matter systems. Programming them may be very will equivalent to constructing them.

Nick Barnes said...

David Lewis,
there are well understood principles of quantum computation, and numerous well-known quantum algorithms following those principles (for example, Shor's algorithm for factorisation: If and when quantum computing with useful numbers of qubits becomes a practical reality, many more algorithms will be developed. Just because *you've* never heard anyone explain it, doesn't mean that it's all woo.

Russell Seitz said...

OpenID 8c7793aa-15b2-11e5-898a-67ca934bd1df was doing much better than usual on QC, until he went all Drexel and tried to turn it into a nanoclock.

Anonymous said...

Drexal was the nano-mechanical guy. It never worked out, obviously. I'm the pico-quantum guy. It works fine as long as you allow for the BCS-BEC crossover, geometry, toppology and duality. It's gonna be fun, especially watching all the old fuddy duddies like yourself freak out.

Russell Seitz said...

" Physically implementing a very large and complex quantum computer is going to require a combination of natural and directed atomic self assembly and active machining of the resulting structures to tailor them to a specific task. These are neural networks implemented in solid state and condensed matter systems. "

Sounds like Drexel pur sang, which very yawn making.because above zero K quantum effects are very bad for molecular machines that get stuck in bad states one atom at a time

Anonymous said...

No, Russell, Drexler was about about mechanical nanoassemblers, self assenbly of bismuth pico-islands has already been demonstrated. and it's the topological edge states that form and process the qubits. It's distincly non-abelian statistics that are going to freak you out. Try following these guys : and

Remember, I'm also the Group V guy, the electrohydride guy, and the atomene and elemene guy. Besides the bismuth iodide guy. You're the old guy.

Thomas Miconi said...

The Fermi Thermodynamics book is awesome!

If there's a similarly simple, straightforward and self-contained book for stat mechs (or anything physics-wise really) I'd be glad to hear about it!