Quantum Multiplexer

The split gate transistor was invented 22 years ago and has ben in wide-spread use ever since in the investigations of the fundamental physics of electron transport in low-dimensional structures. At most a few such transistors have ben used in very small circuits. We have devised a way of making over 1000 split gate devices on the same chip and the way to bias each gate, while needing only 40 contacts to read out the transport properties of the entire array. This advance will greatly accelerate both the physics investigations and the exploration of new device concepts, taking fully into account a statistical analysis of the results as a function of the intrinsic fluctuations from gate-to-gate.

The following is abstracted from the attached Impact Statement. We note: (i) The quantum multiplexer is likely to give a major boost to areas as diverse as metrology, quantum computing, quantum information processing, cryptography and the basic physics as well. It will be a flexible research tool capable of being engineered into a useful general purpose device. It represents the first major advance since the original slit-gate transistors and the following experiments involving a few such gates. There is an enormous range of possible experiments on devices, circuits and statistical physics that will be enabled. It is the quantum version of a gate array, the classical version of which is in very widespread use in conventional electronics. The modern ITEC industry has a multi-$T annual budget. (ii) Getting a fully working multiplexer with associated modelling and simulation capability will require us to prove a number of points that are just beyond today's state-of-the-art, in particular the handling of many interacting potential wells as we set the gates to some agreed 'zero'. The organisation of this process may well have spin-offs into combinatorial optimisation more generally. (iii) Although many of the quantum applications in IT may be some way off, there is an immediate application in quantum metrology which has been identified and we will be working jointly with NPL on this aspect. The quest to achieve adequate accuracy for counting electrons as a measure of the current needs to be improved by 2-3 orders of magnitude, and the multiplexer is certain to give a contribution to that improvement: just how much remains to be seen. (iv) The training opportunities for both the post-doc and the research student are broad and highly advantageous. They will be exposed to growth, fabrication, design, test, and the use of low temperatures and high magnetic fields. The link with NPL will show how research can be focussed to an identified end-goal. The physics aspect is at the forefront of quantum transport of electrons in semiconductors, and may open up new areas in statistical physics. This will interest many international laboratories and give the two new researchers world-wide exposure. (v) This project highlights the links between physics and engineering in this subject and will make a good case study for widespread dissemination. We intend to use the work on outreach programmes within Cambridge, as we attract more STEM students to the university. (vi) There are important possibilities for producing, capturing and exploiting new intellectual property. The investigators all have experience of this in academia and in industry, both start-ups and large companies. If the multiplexer catches on in the way the original split-gates did there will be a business in producing and selling these as R&D samples.