Dr Edward Laird
Department of Materials
Tel: +44 1865 273769 (Room 195.20.09)
Tel: +44 1865 273700 (switchboard)
Fax: +44 1865 273789 (general fax)
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Quantum mechanics is not only fascinating in its own right, but also offers the possibility of revolutionary applications. I create electronic devices that exploit quantum behaviours of superposition and entanglement. I aim both to develop new technology and to explore fundamental science in quantum engineered devices. I use techniques of nanofabrication, quantum transport, and spin resonance.
Quantum computing devices based on carbon nanomaterials
Dr. E.A. Laird
Although present-day computers rely heavily on the laws of quantum physics that determine the behaviour of semiconductors, they make no use at all of the key quantum resources of superposition and entanglement. Electronic devices that exploit these resources would open the way to performing important but currently intractable calculations. I will develop quantum electronic devices using two carbon-based materials uniquely suited for this purpose, carbon nanotubes and endohedral fullerene molecules (endofullerenes). My quantum bit will be the magnetism (spin) of a single conduction electron in a nanotube, which I will control and read out electrically. I will read and write the state of this bit onto the state of an endofullerene molecule embedded in the nanotube, where it is protected from damaging environmental interactions. For even stronger protection, I will transfer the quantum state to a single nucleus of the endofullerene, an outstanding quantum memory capable of preserving a superposition for many milliseconds. This project extends Oxford’s current expertise in ensemble quantum computing by controlling individual quantum systems for the first time. As well as long-term applications in quantum computing and quantum simulations, this technology is also well suited for building sensitive microscopic magnetometers. This project is funded by the Royal Academy of Engineering
1 public active projects
For an up-to-date list of publications, see http://users.ox.ac.uk/~oums0769/index.htm
Chip-based atomic clocks
Dr E. A. Laird / Professor G. A. D. Briggs
Atomic clocks are among the most precise scientific instruments ever made, and are key to advanced navigation, secure communication, and radar technology. We are pursuing a new approach to create a clock that will fit on a chip. Instead of atomic vapours, we will use electron and nuclear spins in endohedral fullerene molecules, whose energy levels offer an exquisitely stable frequency reference. To make this novel approach work, we must overcome a range of physics and engineering challenges, including detecting spin resonance from a small number of spins, identifying the energy levels involved, and miniaturizing the control electronics and magnet. The reward will be a completely new technology with a wide range of civilian and military uses. We are looking for a candidate who has a strong interest in applying quantum physics in new technology, and is motivated to develop the new and demanding electronic measurement techniques that will be necessary.
Putting the mechanics into quantum mechanics: creating superpositions of motion using vibrating carbon nanotubes
Dr E. A. Laird / Dr N. Ares / Professor G. A . D. Briggs
The quantum mechanics of microscopic objects such as atoms and spins is well established. But what about larger objects? Can we verify true quantum behaviour for these?
As a first step to answering this question, we plan to create and measure quantum superpositions of nanoscale mechanical devices. Although tiny by everyday standards, even the smallest fabricated device contains thousands of atoms. We will make use of suspended vibrating carbon nanotubes. These possess many attractive features for creating mechanical quantum superpositions, including low mass, large quantum level spacing, and comparatively large zero-point motion. Our goal is to carry out a foundational test of quantum mechanics – the Leggett-Garg test – that falsifies the hypothesis of classical behaviour in this device. This project will focus on creating and probing so-called “macroscopically distinct” superpositions, such as a superposition of zero and ten phonons in the same device. These challenging experiments on tiny devices are the first step on a long road to discovering whether quantum mechanics applies to macroscopic objects.
Bench-top experimental tests of gravitation in quantum systems
Dr N. Ares / Dr E. A. Laird / Professor G. A. D. Briggs
The territory where quantum mechanics has to be reconciled with gravitation is still experimentally unexplored. Gravitational effects in quantum systems are typically small, making laboratory-scale experiments extremely challenging. Advances in mechanical resonators at the micro-scale and cryogenic temperatures are beginning to bring such experiments within reach. We plan to evaluate the feasibility of bench-top experiments based on two micromechanical oscillators to explore the effect of gravity in quantum systems.
Heating of mechanical resonators is expected from gravitational decoherence. To determine whether this heating effect can be measured, we will build the world’s most sensitive calorimeter based on an optomechanical system at cryogenic temperatures. The optomechanical system will consist of two mechanical oscillators inside a 3D microwave cavity, whose interaction will allow for measurement of the mechanical oscillators’ temperature. The microwave cavity will be fabricated in an aluminium block and the mechanical resonators will be commercially available silicon nitride membranes with excellent mechanical properties.
This is an ambitious project with the goal of elucidating whether quantum gravitational effects can arise in table-top experiments, opening up the possibility for a whole new direction for the quest of quantum gravitational effects.
Carbon-based quantum devices characterised electrically and by imaging
Dr E. A. Laird, Dr J. H. Warner and Professor G. A. D. Briggs
Carbon nanomaterials are attractive materials for electronic devices, especially for quantum computers using the spin of single electrons. One challenge in realising these applications is that the detailed device structure cannot be fully controlled during fabrication. The aim of this project is to characterize the same devices both through electrical measurements and by high-resolution electron microscopy, with the aim of understanding the electronic properties in terms of the atomic structure.
The goal of project will be to determine how the bandstructure and spin-orbit coupling of carbon nanotubes depend on the atomic structure – in particular on the chirality, which describes how the carbon atoms are aligned. Through aberration-corrected high-resolution transmission electron microscopy (AC-HRTEM), it is possible to measure the chiral indices of individual nanotubes, but so far this has not been performed on nanotubes integrated into electronic devices. You will combine these two kinds of measurement by incorporating a TEM window into existing fabrication technology for ultra-low-disorder nanotubes. You will then make electrical measurements of selected devices in a dilution refrigerator, with the aim of correlating the measured spin-orbit coupling to the previously determined chirality and comparing with existing theoretical predictions.
Nanomaterials for quantum technologies
Professor G. A. D. Briggs, Professor K. Porfyrakis, Professor J. H. Warner and Dr E. A. Laird
Quantum information processing offers one of the most exciting challenges in the study and development of nanomaterials. It is at the cutting edge of quantum nanoelectronics, and Oxford is part of the world-wide endeavour to develop scalable quantum computers. Instead of classical bits of information, these will work with qubits (quantum bits). We need materials with quantum states that can be individually controlled and measured, and yet which are sufficiently robust against decoherence that they can sustain a sequence of quantum manipulations and interactions. We lead the world in using the new family of fullerene materials (popularly known as Bucky balls), which can be used to contain atomic species inside a cage that separates them from the environment. We can store the quantum information in an electron or nuclear spin, and exchange it between the two. We can manipulate and characterize the spin states by electron paramagnetic resonance and also optically. By creating entanglement between several spins, it is possible to develop sensors that exceed the standard quantum limit. A core thrust of our research is to incorporate molecular materials in working devices for practical quantum technologies. There will be several projects with these nanomaterials, ranging from synthesis and microscopy to experimental implementation of candidate schemes for quantum computing. The research is highly interdisciplinary, and there is scope for a range of skills and interests from materials science and chemistry to experimental quantum physics. There may be possibilities for industrial support and for international travel and collaboration.
Also see a full listing of New projects available within the Department of Materials.