Versatile Quantum Multiplexing

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Although we have known about one-dimensional electron transport at semiconductor interfaces for 25 years, little work has been done to investigate complex integrated circuits of such devices, or to evaluation the statistics of yield and reproducibility of the quantum effects seen in different devices, and so discern if manufacturable circuits might be possible.We have developed a way of making a fully addressable 16x16 array of split-gate transistors (also known as quantum point contacts), and we have used this to study the fabrication and functional yield of these devices, and to make the first full statistical analysis of the so-called '0.7 spin phenomenon' in the ballistic 1D conductance of electrons. We are in the process of making parallel gates used for pumping charge, one electron at a time to produce measureable currents. We are also developing a means of biasing each split gate so that all 256 are at threshold before an experiment starts. This capability opens up a whole new area of physics and real-world technological applications which we now want to exploit to the full. In particular we will be able to study integrated circuits made of many quantum gates where the electrons retain quantum phase coherence from the input to the output of the circuit.In this proposal we want to take our ideas forward to realise quantum metrology applications, examples of real integrated circuits exhibiting quantum coherence throughout, and a whole range of qualitatively new physics of quantum coherent electrons. We want to accelerate the decisions about exploitability by examining yield and reproducibility of devices as an integral part of the initial investigations.Because of the breath of potential, we are developing the capability as a mini-facility and we will invite other research groups to come and use the multiplexer concept to pursue their own experiments with devices we can make and the dedicated evaluation equipment we are bidding for.