Steven Girvin - Quantum Computing

So the field of quantum information is quite new. Quantum mechanics is not new I mean everything that people are excited about now they could have understood in 1927 or 28 when quantum mechanics, the present theory quantum mechanics was more or less fully formulated and, but quantum mechanics is sufficiently bizarre and counter-intuitive and has such unexpected implications that people still don't fully understand it and starting about 20 years ago people began to realize that the weird laws of quantum mechanics could allow you to do computations that are impossible or impossible to do quickly on a classical computer.

So that's interesting just from a theoretical point of view but it turns out that these ideas now are from quantum information are have, are spreading out into other areas of physics and having an impact on things that have nothing to do with trying to build a quantum computer.

So for example people who study condensed matter systems magnets and superconductors systems where there are many, many particles. Let's say many, many electrons it's very difficult to solve a quantum mechanics, to solve the extraordinary equation and predict ahead of time what phenomenon will arise.

Especially, when the particles are strongly interacting like the electrons are repelling each other because of the coolum forces but with the greater understanding of the information content in quantum-mechanical states, people are understanding now much more efficient ways to program classical computers to describe or compute and make predictions about the complicated quantum states of real physical systems containing many strongly interacting electrons.

These ideas are now actually making connections to cosmology and general relativity in a completely surprising and unexpected way. There's a great deal of work here in waterloo at the perimeter institute on these developments.

Also, even before building a quantum computer just some of the ideas about quantum information processing are now helping us build better atomic clocks, more precise clocks and you know read the time from those clocks much more accurately than we could in the past based on new ideas about how to transfer the information in a quantum state from the atoms in the clock to other atoms which are your readout device.

So the, it's still quite unclear whether we can actually build a large-scale quantum computer and it's not even completely clear what such a machine would be good for.

We know certain tasks that it could carry out very rapidly but it's already clear that the intellectual effort around this goal of building a quantum computer has led to side benefits to several areas of physics so its a very exciting time for both theorists and experimentalists.

You know we're in a situation now where things kind of work we've made lots of progress we can manipulate the quantum states of two and three and four superconducting quantum bits but we need to develop tool boxes and build little modules of few qubits that can very reliably carry out certain tasks.

Then we have to develop the protocol for communicating the quantum information between such modules in some fault tolerant way and you could think about scaling up some of the current designs but we know if you built a million of them it's not going to work.

You could think about perfecting the little module with two or three quantum bits until it's really working but if you forget about, if you forget that when you're done it has to be able to communicate with other parts of the system you may find you went up a blind alley. so it's very, very tricky to when the, when the details of the technology have not yet been settled to think about how you're going to scale this thing up.

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