Engineering Quantum Technology Systems on a Silicon Platform

The vision of this project is to develop practical quantum technology for the accurate measurement of electrical currents and to develop high sensitivity detectors for gases such as carbon dioxide, methane (the gas used to heat homes) and carbon dioxide. Single electron transistors allow only one electron to travel through the device when switched on to form the electrical current. If the control gate is switched at a high frequency then the current through the device is simply the frequency times the charge on an electron and by counting the number of electrons, the current can be accurately measured. All such devices to date only work at low temperatures due to the small energy difference between the quantum states required for the transistor. I am proposing to make a single electron transistor which is far smaller than any previous reported device that will have large energies between the quantum states and operate at room temperature. Gas molecules absorb light at very specific wavelengths which in the mid-infrared part of the electromagnetic spectrum correspond to vibrational energy of the bonds which hold the atoms together to form the gas molecule. This provides a molecular fingerprint as each molecule only absorbs specific wavelengths which can therefore be used to identify the gas. Gas detectors already exist for carbon dioxide, carbon monoxide and methane gas by measuring the absorption of light at the molecular fingerprint wavelength but the sensitivity for small battery powered detectors in the home is at the level of parts per million. For many scientific, healthcare, industrial and security applications sensitivities require to be at least a thousand times better. To date systems for measuring at this accuracy are large, bulky and require large lasers. This proposal will use quantum technology to build a far smaller and cheaper chip scale gas detector with parts per billion sensitivity that could be integrated into mobile phones or used for battery power sensors. I am proposing to use the quantum nature of light to produce 2 individual packets of light called photons which will be at the same wavelength and at the same phase where the peaks and troughs of the waves are at the same points in space as the light travels through a waveguide. Heisenburg's uncertainty principle only allows us to measure the amplitude or the phase of the photons with a specific accuracy and the product is a constant. If we squeeze the phase of the light so that the accuracy in measuring the phase is reduced then we can measure the amplitude more accurately since it is only the product of the two that we cannot measure at a higher accuracy. This quantum approach of squeezing light allows far more sensitive measurements that are forbidden in classical measurement systems. The project brings together a range of UK companies, government agencies, standards laboratories and universities to deliver the portable current standard and the high sensitivity gas detector. I will be supplying demonstrators to a range of collaborators who will evaluate the performance with successful devices being transferred to UK companies to help develop next generation products. The project will also train 2 research associates and 2 PhD students in quantum technology.