Coherent Optical and Microwave Physics for Atomic-Scale Spintronics in Silicon (COMPASSS)

Lead Research Organisation: University of Surrey
Department Name: ATI Physics

Abstract

Silicon and the technology developed with it has revolutionised industry, entertainment and communication, and there is always interest in new ways to remember and process information. The challenge is to find methods of encoding information in the smallest possible volume and manipulating it in the most complex ways with the lowest energy cost and the highest speed. In this programme, we shall develop methods for encoding information in a single electron, orbiting a single impurity atom in a silicon crystal. We shall develop the technology for manipulating that information with terahertz speed by its magnetic connection with adjacent impurity electrons.At the same time our work will produce a new way of studying atomic physics, which, at its most exciting, requires that single atoms are trapped in a vacuum by complex combinations of laser beams and electro-magnetic fields. Recent interest in atomic physics has centred around the detailed control of quantum states in atoms. Quantum physics allows an electron to be in two places or two states at once, and also allows two electrons to be in a single entangled state where examination of one electron gives up full knowledge of the other. Experiments with pulsed visible lasers on atoms trapped in vacuum have demonstrated new phenomena based on this principle. Similar physics applies to the nucleus, and has resulted in the technology of NMR and MRI. Impurities in crystals, if they have substituted one of the host atoms, can sometimes be thought of just in terms of their extra charge. For example, phosphorus impurities in silicon crystals look like silicon atoms with an extra proton in the nucleus and an extra electron. The extra electron orbits around the extra proton charge in a very similar way to the orbit of the electron around a proton in a hydrogen atom. The energies of the allowed orbits follow the same pattern (the Rydberg series) except that the transitions are in the far-infrared, as opposed to the visible/X-rays for hydrogen. Our programme will extend the analogy between the atom trap and the impurity in a crystal. For example we will demonstrate that electrons can be put into two states at once - an electronic version of the trigger that caused Schrodinger's famous cat to be both alive and dead at the same time-and that they can live in this superposition for long times. Recently, atomic physicists have been trying to minaturise their traps using silicon technology to manipulate the atoms in free space just above an atom chip . In a sense, we are working on a similar problem with the atoms held just below the surface instead of just above it. This has the advantage that the impurities are permanently fixed, that complex and new molecule states can be made with adjacent impurities, and that we can take full advantage of the processing technologies in the world's best developed material. The experiments are all enabled by the Free-Electron Laser FELIX facility near Utrecht. This kind of laser (which does not yet exist in the UK) is analogous to the pulsed visible lasers used for the atomic physics experiments, but gives out far-infrared pulses suitable for impurity atoms in silicon. Our proposal takes advantage of the fact that FELIX provides very high power, very short pulsed light that is coherent and tunable. The magnetic interactions between adjacent impurity electrons will be produced by exciting them with FELIX, but to measure the resulting changes we need microwave pulses and a magnet to perform electron paramagnetic resonance (EPR). We will install an EPR spectrometer at FELIX for this purpose. The equipment will also have enormous potential for applications in biology, since EPR is used extensively for measuring the configuration of large bio-molecules, while far-infrared laser pulses can induce controlled changes in conformation. Although we will concentrate on the atomic physics, a spin-out programme in biology will result.

Planned Impact

The major initial beneficiaries will be the science and engineering communities, ranging from those interested in basic quantum physics through to molecular biologists. There is also a set of technique-oriented scientists who will profit because of the development of new uses for electron accelerator-based light sources. Others who will stand to gain over the intermediate to long term include private companies and investors in an equally large variety of sectors, including but not limited to providers of analytical equipment for biomedicine, THz generators, semiconductor devices and software for integrated circuit design. UK society and wider economy will benefit from the unique training opportunities provided by COMPASSS to PhD students and PDRA's. Finally, the general public both in the UK and worldwide will gain broad understanding of the adventure that is cutting edge science and engineering of the sort that we are proposing in COMPASSS. Both universities have excellent track records in third stream activities (Knowledge & technology transfer). A collaboration agreement will be prepared to deal with the management of new and background IP. The universities have strong business development activities promoting interaction with industry and commercial investors (eg Surrey's EPSRC 10M KTA platform, LCN full-time business development manager), while both are actively involved in the public awareness of science. We already have partnerships in place as described in the corporate letters of support. In particular, non-disclosure agreements have allowed us to discuss plans with Qualcomm, IBM and Agilent, all of whom will move towards more detailed commitment and exploitation agreements should the project be funded. Prof Jim Al-Khalili, holds the Chair in Public Engagement in Science at Surrey, and his remit will be to promote the science and its benfeifts to the general public. As a result of the new applications we anticipate much enhanced interest from the public in atomic physics. His role fits in well with aims of the recently established South East Physics Network in promoting the value of physics to the widest possible audience.

Publications

10 25 50
 
Description Next to iron and ice, silicon is the most important inorganic crystalline solid because of the tremendous ability to control electrical conduction via chemical and electrical means. The associated devices - most notably the field-effect transistor - can all be understood using only the semi-classical band theory of solids. There are currently no IT technologies that utilise the ability of electrons to be in two states at once. This ability is encountered regularly in medical physics because it is the effect that makes MRI possible. We envisage devices where "quantum information" - where electrons represent both a 1 and a 0 at the same time - can be transferred along chains of impurities in silicon, manipulated, and read out electrically. This requires control of quantum coherence in semiconductor nanostructures where many identical units can be coupled and electrically contacted. In this project we have developed the technology to position individual phosphorus impurity atoms in the crystal one-by-one with atomic precision. We have also learned how to coherently control the orbital and spin quantum numbers. Finally we have demonstrated that we can read out the orbital and spin electrically (albeit in ensembles, though with greatly reduced size in recent experiments on as few as 10,000 atoms).
Exploitation Route Quantum computing has the potential to calculate much more quickly some kinds of things that would be impossible with standard computers. Because the subject is so new there have not been a great number of specific programs written, but the main example is in information security. Quantum computing will enable cracking of standard codes, but will also be able to produce uncrackable codes.

It has been suggested that quantum computers will be much better for problems where quantum physics is key, such as in medicine where the problem of molecular bonding must be solved in designing new drugs. It will also be much better for solving problems where very large amounts of information need to be manipulated, such as climate science modeling.
Sectors Aerospace, Defence and Marine,Digital/Communication/Information Technologies (including Software),Education,Pharmaceuticals and Medical Biotechnology

URL http://www.compasss.net
 
Description Programme Grant "Atomically Deterministic Doping and Readout For Semiconductor Solotronics (ADDRFSS)"
Amount £8,076,161 (GBP)
Funding ID EP/M009564/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Academic/University
Country United Kingdom
Start 02/2015 
End 01/2020
 
Title Controlling electronic access to the spin excitations of a single molecule in a tunnel junction 
Description STM data related to the paper: Controlling electronic access to the spin excitations of a single molecule in a tunnel junction Ben Warner, Fadi El Hallak, Henning Prüser, Afolabi Ajibade, Tobias Gill, Andrew J Fisher, Mats Persson, and Cyrus F Hirjibehedin Nanoscale (2017) 
Type Of Material Database/Collection of data 
Year Produced 2017 
Provided To Others? Yes  
Impact None to date. 
URL http://doi.org/10.6084/m9.figshare.c.3699211
 
Title Metallic atomically-thin layered silicon epitaxially grown on silicene/ZrB2 
Description STM data used in the referenced paper: Metallic atomically-thin layered silicon epitaxially grown on silicene/ZrB2 Tobias G. Gill, Antoine Fleurence, Ben Warner, Henning Prüser, Rainer Friedlein, Jerzy T. Sadowski, Cyrus F. Hirjibehedin and Yukiko Yamada-Takamura 2D Materials 4, 021015 (2017) 
Type Of Material Database/Collection of data 
Year Produced 2017 
Provided To Others? Yes  
Impact None to date. 
URL http://doi.org/10.6084/m9.figshare.c.3688366
 
Description Invited Talk: MicroScience 2010, Scanning Probe Microscopy (UKSPM), London, UK 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Type Of Presentation keynote/invited speaker
Geographic Reach National
Primary Audience Professional Practitioners
Results and Impact A nice meeting of national (and some international) scientists in scanning probe techniques and applications.

A great chance to become more familiar with the national community in scanning probe measurements. Led to establishment of good national contacts.
Year(s) Of Engagement Activity 2010
 
Description Organising Committee Member, 39th International Conference on Micro and Nano Engineering (MNE2013) 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Type Of Presentation workshop facilitator
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact A very successful international conference series being run in the UK for the first time in over a decade.

This was a great opportunity for me to become more familiar with large conference organisation and I have chaired several workshops since this drawing on my experience.
Year(s) Of Engagement Activity 2013
URL http://www.mne2013.org/
 
Description Royal Soc summer 2011 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? Yes
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact It sparked a lot of interaction, particularly around the idea of being in two places at once. The exhibit resulted in several national and local radio interviews to discuss the ideas behind it.

The exhibit sparked interest from VIP visitors e.g. Prof Sir Paul Nurse (President of the Royal Society), Prof Cyril Hilsum FRS (Defence Scientific Advisory Council), Prof Sir Peter Knight FRS (President of IoP) etc. It was seen at the RS and later science festivals by 30,000 school children
Year(s) Of Engagement Activity 2011,2012
URL https://royalsociety.org/summer-science/2011/quantum-computing/
 
Description economist 2010 
Form Of Engagement Activity A magazine, newsletter or online publication
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Media (as a channel to the public)
Results and Impact A press release about our activity sparked media interest

An article appeared in the Economist resulting from an interview about a publication of ours.
Year(s) Of Engagement Activity 2010,2013
URL http://www.economist.com/node/16422424
 
Description economist 2013 
Form Of Engagement Activity A magazine, newsletter or online publication
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Media (as a channel to the public)
Results and Impact press release sparked media interest

an article was written in the economist about our research activity following an interview
Year(s) Of Engagement Activity 2013
URL http://www.economist.com/news/science-and-technology/21573529-small-models-cosmic-phenomena-are-shed...
 
Description feature article in Nature Physics: News and Views 
Form Of Engagement Activity A magazine, newsletter or online publication
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Media (as a channel to the public)
Results and Impact News and Views article in Nature Physics highlighting "Control of single-spin magnetic anisotropy by exchange coupling" article published in the same issue.

More people became interested in the interaction of magnetic adsorbates with surfaces.
Year(s) Of Engagement Activity 2013
 
Description public outreach at the Wellcome Collections Miniatures Event 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact Participation in a public event organised by the Wellcome Collection. We explained molecular spintronics, and more broadly nanotechnology research, to many members of the general public who attended the event.

Stimulated interest in nanotechnology in many members of the public.
Year(s) Of Engagement Activity 2012