Research generalities (I)

I thought I'd explain a bit about what I do in my research. This will be a general overview really, I'll probably go into specifics at another time...

I'm currently working on experimental investigations into Macroscopic Quantum Tunneling in superconductors at mK temperatures, for qubit (quantum computing) and microwave applications. Specifically I look at Josephson Junctions, although there are other systems in which the phenomenon can be observed.

Why is this interesting?

Well, superconductors are one of the few examples of a system exhibiting a macroscopic quantum wavefunction. That is, a macroscopic number of electrons (for example 10^6 rather than the few in an atom or likewise) form a coherent quantum state, and you can make measurements of quantum variables by measuring more familiar quantities such as voltage and magnetic flux. Which is what I do. More about this on a later date I feel.

Here is a picture of a typical experimental setup:

This shows the dilution refrigerator (one of the group's fridges) up and running. The temperature is 105mK, not sure if it's possible to read that or not :) It actually looks a bit swankier now, I have a nicer rackmount and some microwave kit and things, this photo is quite old!

Here's a picture of the inside of the inner vacuum can showing some of the wiring and the filtering of the DC lines:

The device to be measured is in the centre of the copper box at the bottom, well shielded from the environment which would cause decoherence in qubits and add unwanted noise in the MQT experiments.

At the moment we are measuring some novel junction systems in addition to improving the measurement system for conventional Niobium junctions.

I'll put some more pictures up soon, of the devices and different fridges. I have lots :) You'll have to excuse my slight biasing towards the dilution refrigerator though (colloquially known as Frosty) because I spent the majority of my PhD working on this piece of apparatus so I have a slight emotional attachment!