Personal Homepages

George Briggs

Professor Andrew Briggs
Professor of Nanomaterials

Department of Materials
University of Oxford
16 Parks Road
Oxford OX1 3PH

Tel: +44 1865 283336 (Joyner D'souza PA)
Tel: +44 1865 273725 (Room 195.30.05)
Tel: +44 1865 273777 (reception)
Fax: +44 1865 273730

QuEEN Programme
Personal Page

Summary of Interests

Summary of Interests

Whenever a fundamental new principle of science is discovered, the chances are that sooner or later a way will be found to use it for a new technology. The quantum mechanical principles of superposition and entanglement, identified nearly a century ago, are now understood to offer spectacular potential for technological applications. Superposition describes how an object can be in two states at once, as it were "here" and "there" at the same time. Two or more objects in superposition states can be entangled, so that measurements on each of them are correlated in a way that goes beyond anything we would expect from everyday intuition. Exploiting these effects in practical devices would provide new capabilities for fields such as molecular light harvesting and for molecular quantum technologies such as sensors, simulators, and quantum computers.

Successful laboratory experiments have shown that molecules of various kinds can exhibit these crucial quantum properties. Molecules are composed of electrons and atomic cores or "nuclei". Both electrons and nuclei can have a property called spin associated with them that makes them behave like tiny bar magnets. We have confirmed that electron and nuclear spins can be put into superpositions or entangled, and they can last for a long time in that condition. Most of the experiments so far have been in small test tubes. The crucial step now is to implement the same effects in nanometre scale electrical devices, such as single electron transistors consisting of single sheets of carbon rolled up as nanotubes or flat as sheets of graphene. By making hybrid technologies that combine molecules with nanoelectronics, we will lay the foundation for scaling up to more complex systems.

At this very small size, different atoms or molecules in different places affect the behaviour of the device. A breakthrough in the past few years enables us to see the positions of individual atoms in the materials which we want to use in our devices. The technique is aberration-corrected electron microscopy, and provided the electrons are not too energetic it is possible to look at the structures which we have made without damaging them. In this way we shall be able to relate the device performance to the atomic resolution microscopy of the component materials. Individual components of this vision include the following.

  1. design the devices to build, based on a deep understanding of how to control their quantum states;
  2. produce the materials, such as molecules with suitable spin states with carbon nanotubes and graphene for electrical substrates;
  3. make nanoscale devices and examine them in a microscope to see where the individual atoms and molecules are;
  4. perform the experiments to develop the quantum control and measurement for the effects which we aim to exploit;
  5. undertake theoretical modelling to understand the electron behaviour and to design new materials systems for improved performance.

Prizes and Awards

  • Holliday Prize, Institute of Materials, 1984
  • Metrology award for World Class Manufacturing, 1999
  • Honorary Fellow of Royal Microscopical Society, 2000

Recent Lectures

Current Research Projects

Quantum Effects in Electronic Nanodevices
Professor G.A.D Briggs, Dr L. Bogani, Dr J. Mol, Professor H. Anderson, Professor C. Lambert
Electronic devices, when shrunk to the molecular scale, display prominent quantum effects. Within the QuEEN programme we shall develop the scientific understanding and technological know-how needed to exploit these quantum effects for reduced-energy computing, molecular recognition, universal memory and thermoelectric recovery of energy. Our research will concentrate on the underpinning science of stable and reproducible devices, consisting of single molecules connected to graphene electrodes, with the potential for scalable production. We aim to harness quantum interference in these devices by pursuing five complementary research challenges: 1. How can quantum interference in a molecule be controlled by an electrostatic gate? 2. Can spintronic effects provide superior molecular devices? 3. Can quantum interference be used to achieve high thermoelectric effects? 4. What are the performance limits for a single-molecule transistor? 5. Can we make single molecule devices that work in ambient conditions? The QuEEN programme combines chemical synthesis, nanofabrication, measurement, and theory, and integrates these different areas of expertise. QuEEN has a distinguished international Board and a range of industrial partners from local enterprises to established global firms.

1 public active projects

Research Publications


Realization of a Carbon-Nanotube-Based Superconducting Qubit. M. Mergenthaler, A. Nerisyan, A. Patterson, M. Esposito, A. Baumgartner, C. Schoenberger, G.A.D Briggs, E.A. Laird, P.J. Leek. [PDF]

Radio-frequency optomechanical characterization of a silicon nitride drum. A. Pearson, K.E. Khosla, M. Mergenthaler, G.A.D. Briggs, E. A. Laird, N. Ares. [PDF]

Understanding electron transfer on the single-molecule level, J.O. Thomas, B. Limburg, J.K. Sowa, K. Willick, J. Baugh, G.A.D. Briggs, E.M. Gauger, H.L. Anderson and J.A. Mol. [PDF]

High pressure electron spin resonance of the endohedral fullerene 15N@C60. T. Harding, 1.A. Folli, J. Zhou, G.A.D. Briggs, K. Porfyrakis and E.A. Laird. [PDF]

Radio-frequency reflectometry of a quantum dot using an ultra-low-noise SQUID amplifier. F.J. Schupp, N. Ares, A. Mavalankar, J. Griffiths, G.A.C. Jones, I. Farrer, D.A. Ritchie, C.G. Smith, G.A.D. Briggs and E.A. Laird. [PDF]

Efficiently measuring a quantum device using machine learning. D.T. Lennon, H. Moon, L.C. Camenzind, L. Yu, D.M. Zumbühl, G.A.D. Briggs, M.A. Osborne, E.A. Laird and N. Ares. [PDF]

A wide-band tunable phase shifter for radio-frequency reflectometry. G. Yin, G.A.D. Briggs and E.A. Laird[PDF]






Atomic scale imaging of reversible ring cyclization in graphene nanoconstrictions. ACS Nano 13, 2379-2388 (2019); DOI: 10.1021/acsnano.8b09211. J.K. Lee, G.-D. Lee, S. Lee, E. Yoon, H.L. Anderson, G.A.D. Briggs and J.H. Warner. [PDF]

Quantum Interference in Silicon 1D Junctionless Nanowire Field-Effect Transistors F. J. Schupp, M.M. Mirza, D.A. MacLaren, G.A.D. Briggs, D.J. Paul, and J.A. Mol. Phys.Rev.B., 23, 235428 (2018) [PDF]

Ethical considerations in the era of gene synthesisMedNous8-10 January 2019. G.A.D Briggs, T Brears § [PDF]

Geometrically Enhanced Thermoelectric Effects in Graphene Nanoconstrictions. A. Harzheim, J. Spiece, C. Evangeli, E. McCann, V. Fal'ko, Y. Sheng, J. Warner, G. Briggs, J. Mol, P. Gehring, O. Kolosov. Nano Letters, 2018. [PDF]

Beyond Marcus theory and the Landauer–Bütiker approach in molecular junctions: A unified framework.  J.K. Sowa, J.A. Mol, G.A.D. Briggs and E.M. Gauger. Chem. Phys. Editor's Pick, October 2018 [PDF]

Measuring carbon nanotube vibrations using a single-electron transistor as a fast linear amplifier. Y. Wen, N.  Ares, T. Pei, G.A.D. Briggs and E. A. LairdAppl. Phys. Lett.113, 153101 (2018) [PDF]

Anchor groups for graphene-porphyrin single-molecule transistors. B. Limburg, J.O. Thomas, G. Holloway, H. Sadeghi, S. Sangtarash, I.C.-Y. Hou, J. Cremers, A. Narita, K. Müllen, C.J. Lambert, G.A.D. Briggs, J.A. Mol and H.L. Anderson.  Adv. Funct. Mater. 2018, 1803629 [PDF]

Low-Frequency Noise in Graphene Tunnel Junctions. P. Puczkarski, Q. Wu, H. Sadeghi, S. Hou, A. Karimi, Y. Sheng, J.H. Warner, C.J. Lambert, G.A.D. Briggs and J.A. Mol.  ACS Nano September 2018 [PDF]

Distance Measurement of a Noncovalently Bound Y@C82 Pair with Double Electron Electron Resonance Spectroscopy. G. Gil-Ramírez, A. Shah, H. El Mkami, K. Porfyrakis, G.A.D. Briggs, J.J.L. Morton,  H.L. Anderson and J.E.  Lovett. J.Am.Chem.Soc. June 2018 [PDF]

Seeing opportunity in every difficulty: Protecting information with weak value techniques.  G.C. Knee and G.A.D. Briggs.  Quantum Stud.: Math.Found. (2018) [PDF]

Spiro-Conjugated Molecular Junctions: Between Jahn-Teller Distortion and Destructive Quantum Interference. J.K. Sowa, J.A. Mol, G.A.D. Briggs and E.M. Gauger. J.Phys.Chem.Lett.9, 1859−1865 (2018) [PDF]

The spin resonance clock transition of the endohedral fullerene 15N@C60.R.T. Harding, S. Zhou, J. Zhou, T. Lindvall, W.K. Myers, A. Ardavan, G.A.D. Briggs, K. Porfyrakis, E.A. Laird. Phys.Rev. Lett. 119, 140801 (2017) [PDF]

Field-effect control of graphene−fullerene thermoelectric nanodevices. P. Gehring, A. Harzheim, J. Spièce, Y. Sheng, G. Rogers, C. Evangeli, A. Mishra, B.J. Robinson, K. Porfyrakis, J.H. Warner, O.V. Kolosov, G.A.D. Briggs and J.A. Mol. Nano Lett. (2017) [PDF]

Conditioned spin and charge dynamics of a single electron quantum dot. E. Greplova, E.A. Laird, G.A.D. Briggs and K. Mølmer.  Phys. Rev. A. 96, 052104 (2017) [PDF]

Environment-Assisted Quantum Transport through Single-Molecule JunctionsJ.K. Sowa, J.A. Mol, G.A.D. Briggs and E.M. Gauger. Phys. Chem.Chem.Phys. 19, 29534 (2017) [PDF]

CF2-bridged C60 dimers and their optical transitions.  P. Dallas, S. Zhou, S. Cornes, H. Niwa, Y. Nakanishi, Y. Kino, T. Puchtler, R.A. Taylor, G.A.D. Briggs, H. Shinohara  and K. Porfyrakis. Chem.Phys.Chem. 18, 3540-3543 (2017) [PDF]

Strong coupling of microwave photons to antiferromagnetic fluctuations in an organic magnet. M.Mergenthaler, J. Liu, J.J. Le Roy, N. Ares, A.L. Thompson, L. Bogani, F. Luis, S.J. Blundell, T. Lancaster, A. Ardavan, G.A.D. Briggs, P.J. Leek and E.A. Laird. Phys. Rev. Lett. 119, 147701 (2017) [PDF]

Double dot quantum memristor. Li, G.W. Holloway, S.C. Benjamin, G.A.D. Briggs, J. Baugh and J.A. Mol. Phys. Rev. B 96, 075446 (2017) [PDF]

One dimensional transport in silicon nanowire junction-less field effect transistors. M.M. Mirza, F.J. Schupp, J.A. Mol, D.A. MacLaren, G.A.D. Briggs, D.J. Paul. Sci. Rep. 7, 3004 (2017) [PDF]

Scaling limits of graphene nanoelectrodes. S.G. Sarwat, P. Gehring, G.R. Hernandez, J.H. Warner, G.A.D. Briggs, J.A. Mol, H. Bhaskaran. Nano Lett. 17, 3688−3693 (2017) [PDF]

Quantum memristor based on coupled quantum dots. G.W. Holloway, Y. Ling, S.C. Benjamin, G.A.D. Briggs, J. Baugh,  J.A. Mol. Bull. Am. Phys. Soc. 62 (4), E52.00011 (2017) [PDF]

Distinguishing lead and molecule states in graphene-based single-electron transistors. P. Gehring, J.K. Sowa, J. Cremers, Q. Wu, H. Sadeghi, Y. Sheng, J.H. Warner, C.J. Lambert, G.A.D. Briggs, J.A. Mol. ACS Nano 11, 4739−4745 (2017) [PDF]

Hyperfine and spin-orbit coupling effects on decay of spin-valley states in a carbon nanotube. Pei, A. Pályi, M. Mergenthaler, N. Ares, A. Mavalankar, J.H. Warner, G.A.D. Briggs, E.A. Laird. Phys. Rev. Lett. 118, 177701 (2017) [PDF]

Detecting continuous spontaneous localisation with charged bodies in a Paul trap. Y. Li, A.M. Steane, D. Bedingham , G.A.D. Briggs. Phys. Rev. A, 95, 032112 (2017)[PDF]

Machine learning and the questions it raises. G.A.D. Briggs, D. Potgieter. In From Matter to Life (eds S.I. Walker, P.C.W. Davies, G.F.R. Ellis) pp 468-486, Cambridge University Press (2017); ISBN 978-1-107-15053-9.  [PDF]

Vibrational effects in charge transport through a molecular double quantum dot. J. K. Sowa, J. A. Mol, G.A.D. Briggs. Phys. Rev. B 95, 085423 (2017) [PDF]

Interference-based molecular transistors  Y. Li, J.A Mol, S.C. Benjamin and G.A.D. Briggs. Sci. Rep. 6, 33686 (2016) [PDF]

Resonant optomechanics with a vibrating carbon nanotube and a radio-frequency cavity. N. Ares, T. Pei, A. Mavalankar, M. Mergenthaler, J. H. Warner, G. A. D. Briggs, E. A. Laird. Phys. Rev. Lett. 117, 170801(2016) [PDF]

Charge separated states and singlet oxygen generation of mono and bis adducts of C60 and C70. P. Dallas, G. Rogers, B. Reid, RA Taylor, H. Shinohara, G.A.D. Briggs and K. Porfyrakis. Chem.Phys. 465, 28-39(2016) [PDF]

Photon-assisted tunneling and charge dephasing in a carbon nanotube double quantum dot.  A. Mavalankar,  T.Pei,  J. H. Warner,  G.A.D. Briggs,  and E.A. Laird. Phys. Rev. B [published online] (2016) [PDF]

Quantum Interference in Graphene Nanoconstrictions. P. Gehring, H. Sadegh, S. Sangtarash, C.S. Lau, J. Liu, A. Ardavan, J.H. Warner, C.J. Lambert, G.A.D. Briggs and J. A. Mol. Nano Lett. 16, 4210-4216 (2016) [PDF]

Sensitive Radio-Frequency Measurements of a Quantum Dot by Tuning to Perfect Impedance Matching.  N. Ares, F.J. Schupp, A. Mavalankar, G. Rogers, J. Griffiths, G.A.C. Jones, I. Farrer, D. A. Ritchie, C.G. Smith, A. Cotten, G. A. D. Briggs, and E. A. Laird. Phys. Rev. A. 5, 034011 (2016). [PDF]

Probing the Dipolar Coupling in a Hetero-spin Endohedral Fullerene-Phthalocyanine Dyad. S. Zhou, M. Yamamoto, G. Briggs, H. Imahori, K. Porfyrakis.  JACS 138, 1313-1319 (2016). [PDF]

Redox-dependent Franck-Condon blockade and avalanche transport in a graphene-fullerene nanoelectromechanical oscillator.  C.S. Lau, H. Sadeghi, G. Rogers, S. Sangtarash, P. Dallas, K. Porfyrakis, J.H. Warner, C.J. Lambert, G.A.D. Briggs and J.A. Mol. Nano Letters 16, 170-176 (2015). [PDF]

Three-terminal graphene single-electron transistor fabricated using feedback-controlled electroburning.
P. Puczkarski, P. Gehring, C.S. Lau, J. Liu, A. Ardavan, J.H. Warner, G.A.D. Briggs and J.A. Mol.  Phys. Lett. 107, 133105 (2015). [PDF]

Graphene-porphyrin single-molecule transistors. J.A. Mol, C.S. Lau, W.J.M. Lewis, H. Sadeghi, C. Roche, A. Cnossen, J.H. Warner, C.J. Lambert, H.L. Anderson and G.A.D. Briggs.  Nanoscale 7, 13181-13185 (2015). [PDF]

Violation of a Leggett-Garg inequality with ideal non-invasive measurements.  G.C. Knee, S. Simmons, E.M. Gauger, J.J.L. Morton, H. Riemann, N.V. Abrosimov, P. Becker, H-J. Pohl, K.M. Itoh, M.L. Thewalt, G.A.D. Briggs and S.C. Benjamin. Nat. Commun. 3, 606 (2012). [PDF]

Storage of multiple coherent microwave excitations in an electron spin ensemble.  H. Wu, R.E. George, A. Ardavan, J.H. Wesenberg, K. Mølmer, D.I. Schuster, R.J. Schoelkopf, K.M. Itoh, J.J.L. Morton and G.A.D. Briggs.  Phys. Rev. Lett. 105, 140503 (2011). [PDF]

Quantum computing with an electron spin ensemble.  J.H. Wesenberg, A. Ardavan, G.A.D. Briggs, J.J.L. Morton, R.J. Schoelkopf, D.I. Schuster and K. Mølmer. Phys. Rev. Lett. 103, 070502 (2009). [PDF]

Structural transformation of graphene studied with high spatial and fast temporal resolution.  J.H Warner, M.H. Rümmeli, T. Gemming, B. Montanari, N.M. Harrison, B. Büchner, H. Shinohara and G.A.D. Briggs. Nature Nanotech. 4, 500-504 (2009). [PDF]

Magnetic field sensing beyond the standard quantum limit using 10-spin NOON states.  J.A. Jones, S.D. Karlen, J. Fitzsimons, A. Ardavan, S.C. Benjamin, G.A.D. Briggs and J.J.L. Morton. Science 324, 1166-1168 (2009). [PDF]. Reported in Electronics Weekly 29 April - 5 May 2009, p. 7; This Week in Science 29 May 2009, p. 1115.

Direct imaging of rotational stacking faults in few layer graphene. J.H. Warner, M.H. Rümmeli, T. Gemming, B. Büchner and G.A.D. Briggs. Nano Lett. 9, 102-106 (2009). [PDF]

Towards a fullerene-based quantum computer. S.C. Benjamin, A. Ardavan, G.A.D. Briggs, D.A. Britz, D. Gunlycke, J.H. Jefferson, M.A.G. Jones, D.F. Leigh, B.W. Lovett, A.N. Khlobystov, S. Lyon, J.J.L. Morton, K. Porfyrakis, M.R. Sambrook and A.M. Tyryshkin. J. Phys.: Condens. Matter 18, S867-S883 (2006). [PDF]

Bang-bang control of fullerene qubits using ultra-fast phase gates. J.J.L. Morton, A.M. Tyryshkin, A. Ardavan, S.C. Benjamin, K. Porfyrakis, S.A. Lyon and G.A.D. Briggs. Nature Physics 2, 40-43 (2006). [PDF]

Molecules in carbon nanotubes. A.N. Khlobystov, D.A. Britz and G.A.D. Briggs.  Accounts of Chemical Research 38, 901-909 (2005). [PDF]  Selected as a cover article for the December 2005 issue.

High fidelity single qubit operations using pulsed electron paramagnetic resonance.  J.J.L. Morton, A.M. Tyryshkin, A. Ardavan, K. Porfyrakis, S.A. Lyon and G.A.D. Briggs. Phys. Rev. Lett. 95, 200501 (2005). [PDF]
Selected for the 21 November 2005 issue of Virtual Journal of Quantum Information,; selected for the 21 November 2005 issue of Virtual Journal of Nanoscale Science & Technology,

Chemical reactions inside single-walled carbon nano test-tubes.  D.A. Britz, A.N. Khlobystov, K. Porfyrakis, A. Ardavan and G.A.D. Briggs.  Chem. Commun. 2005, 37-39 (2005). [PDF]
Chosen by editors as Hot Paper (19 November 2004),; chosen by editors for cover story of Issue 1 of 40th Anniversary Year; reported in Blueprint 5, 3 (18 November 2004); New Scientist (23 November 2004); BBC News,;;; (24 November 2004); Iran Daily Newspaper (25 November 2004) p. 4; Financial Times 35621, 13 (26 November 2004);,,, Chemical & Engineering News 82 (48) 7 (29 November 2004);,, (1 December 2004); (13 December 2004); (14 December 2004); Chemistry World 12 (December 2004),; Editor’s Choice, Science 306, 1863 (10 December 2004); Smallest reactor ever, Materials Today 8 (1) 9 (January 2005); “The smallest test tube” in The Guinness Book of World Records (2006). ‘The above article was amongst the top twenty most accessed from the online version of ChemComm during 2005.’

Observation of ordered phases of fullerene in carbon nanotubes.  A.N. Khlobystov, D.A. Britz, A. Ardavan and G.A.D. Briggs. Phys. Rev. Lett. 92, 245507 (2004). [PDF]
Selected for Virtual Journal of Nanoscale Science & Technology.

Optical schemes for quantum computation in quantum dot molecules.  B.W. Lovett, J.H. Reina, A. Nazir and G.A.D. Briggs.  Phys. Rev. B 68, 205319, 1-18 (2003). [PDF]
Selected for Virtual Journal of Nanoscale Science & Technology

InGaN quantum dots grown by metalorganic vapor phase epitaxy employing a post-growth nitrogen anneal.  R.A. Oliver, G.A.D. Briggs, M.J. Kappers, C.J. Humphreys, S. Yasin, J.H. Rice, J.D. Smith and R.A. Taylor.
Appl. Phys. Lett. 83, 755-757 (2003). [PDF]  Selected for Virtual Journal of Nanoscale Science & Technology.

Gas permeation in silicon-oxide/polymer (SiOx/PET) barrier films: role of the oxide lattice, nano-defects and macro-defects.  A.P. Roberts, B.M. Henry, A.P. Sutton, C.R.M. Grovenor, G.A.D. Briggs, T. Miyamoto, M. Kano, Y. Tsukahara and M. Yanaka.  J. Membrane Sci. 208, 75-88 (2002). [PDF]

Surface glass transition temperature of amorphous polymers. A new insight with SFM. V.N. Bliznyuk, H.E. Assender and G.A.D. Briggs.  Macromolecules 35, 6613-6622 (2002). [PDF]

STM experiment and atomistic modelling hand in hand: individual molecules on surfaces of semiconductors.  G.A.D. Briggs and A.J. Fisher.  Surface Science Reports 33, 1-81 (1999). [PDF]

Elastic and shear moduli of single-walled carbon nanotube ropes.  J.‑P. Salvetat, G.A.D. Briggs, J.‑M. Bonard, R.R. Bacsa, A.J. Kulik, T. Stöckli, N.A. Burnham and L. Forró.  Phys. Rev. Lett. 82, 944-947 (1999). [PDF]

Imaging the elastic nanostructure of Ge islands by ultrasonic force microscopy.  O.V. Kolosov, M.R. Castell, C.D. Marsh, G.A.D. Briggs, T.I. Kamins and R. Stanley Williams.  Phys. Rev. Lett. 81, 1046-1049 (1998). [PDF]

Defect structure of nonstoichiometric CeO2(111) surfaces studied by scanning tunneling microscopy.  H. Norenberg and G.A.D. Briggs.  Phys. Rev. Lett. 79, 4222-4225 (1997). [PDF]

Nucleation of “hut” pits and clusters during gas-source molecular-beam epitaxy of Ge/Si(001) in in situ scanning tunneling microscopy.  I. Goldfarb, P.T. Hayden, J.H.G. Owen and G.A.D. Briggs. Phys. Rev. Lett. 78, 3959-3962 (1997). [PDF]

Atomic-resolution STM of a system with strongly correlated electrons: NiO(001) surface structure and defect sites.  M.R. Castell, P.L. Wincott, N.G. Condon, C. Muggelberg, G. Thornton, S.L. Dudarev, A.P. Sutton and G.A.D. Briggs. Phys. Rev. B 55, 7859-7863 (1997). [PDF]

How does a Tip Tap?  N.A. Burnham, O.P. Behrend, F. Oulevey, G. Gremaud, P.J. Gallo, D. Gourdon, E. Dupas A.J. Kulik, H.M. Pollock and G.A.D. Briggs.  Nanotechnology 8, 67-75 (1997). [PDF]
Included in Volume 25 of Nanotechnology (2013) as one of the top ten best papers published to date.

Hydrocarbon adsorption on Si(001): When does the Si dimer bond break?  A.J. Fisher, P.E. Blöchl and G.A.D. Briggs.  Surf. Sci. 374, 298-305 (1997). [PDF]

Adsorption, abstraction, and pairing of atomic hydrogen on Si(100)-(2 × 1). W. Widdra, S.I. Yi, R. Maboudian, G.A.D. Briggs and W.H. Weinberg.  Phys. Rev. Lett. 74, 2074-2077 (1995). [PDF]

Elastic quantum transport through small structures.  T.N. Todorov, G.A.D. Briggs and A.P. Sutton.  J. Phys: Condens. Matter 5, 2389-2406 (1993). [PDF]

An STM study of the chemisorption of C2H4 on Si(001)-(2 × 1).  A.J. Mayne, A.R. Avery, J. Knall, T.S. Jones, G.A.D. Briggs and W.H. Weinberg.  Surf. Sci. 284, 247-256 (1993). [PDF]

A two-dimensional imaging theory of surface discontinuities with the scanning acoustic microscope. M.G. Somekh, H.L. Bertoni, G.A.D. Briggs and N.J. Burton.  Proc. R. Soc. Lond. A 401, 29-51 (1985). [PDF]
Reprinted in Selected Papers on Scanning Acoustic Microscopy (eds B.T. Khuri-Yakub, C.F. Quate), SPIE Milestone Series MS 53, 104-123 (1992).

The effect of anisotropy on contrast in the scanning acoustic microscope. M.G. Somekh, G.A.D. Briggs and C. Ilett. Phil. Mag. A 49, 179-204 (1984). [PDF]


Projects Available

Bench-top experimental tests of gravitation in quantum systems
Dr N. Ares / 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 a mechanical oscillator inside a 3D microwave cavity, whose interaction will allow for measurement of the mechanical oscillator’s temperature. The microwave cavity is fabricated from an aluminium block and the mechanical resonators are 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. 

Also see homepages: Natalia Ares Andrew Briggs

Microwave to optical conversion using molecular magnetic emitters
Dr L. Bogani /Dr E. A. Laird / Professor J. M. Smith / Professor G. A. D. Briggs

Future quantum systems will likely use several elements conceived with different strategies. These elements, such as photonic networks or superconducting circuits, typically operate at extremely different frequencies, and making them communicate is fundamental for integrated quantum devices. Even techniques to coherently connect remotely-located superconducting nodes would necessitate optical signals and is yet to be developed. This project will develop a coherent microwave-to-optical interface within hybrid quantum architectures for large scale distributed quantum computing. The platform will allow interfacing devices consisting of superconducting microwave resonators by coupling them to emitting spin centres. The resulting scheme will thus allow converting quantum information between two completely different regimes, GHz and optical, that are of crucial relevance for networking. The work will comprise the fabrication of nanodevices with superconducting and magnetic properties and their characterization at low temperatures. The thesis is strongly multidisciplinary and candidates from materials, chemistry and physics will be welcome. The work is developed in the context of an international collaboration, so different aspects can be privileged depending on the interests and attitude of the candidate. You will join an active and lively laboratory with an international atmosphere, and will be assisted in developing a personal vision and an autonomous scientific profile, as well as possible industrial links and scientific collaborations. Please refer directly to Dr. Lapo Bogani, Dr. Edward Laird, Prof. Jason Smith or Prof. Andrew Briggs for details.

Also see homepages: Lapo Bogani Andrew Briggs

Efficient quantum device tuning using machine learning
Dr N. Ares / Professor G. A. D. Briggs

Fault-tolerant quantum computers require hundreds to millions of physical qubits to be operated with high fidelity. Inevitable hardware imperfections must be tuned away through iterative interplay of characterization, simulation, and parameter refinement, with each data point informing the decision of what to measure next. The technology is only scalable if this task can be efficiently automated. Recent progress in machine learning, currently one of the most rapidly developing fields of computing, makes it possible to automate the entire process. This project will apply these new techniques experimentally, working with leaders in machine learning.

The objective is to achieve automated tuning of semiconductor qubits encoded in gate-defined quantum dots. These qubits are an ideal testbed because the physics is known and the device parameters are conveniently optimized by gate voltages. Nonetheless, tuning a simple device by hand takes days to weeks, which is clearly not scalable.  We expect this machine learning approach to enable the tuning of large quantum circuits.


Also see homepages: Natalia Ares Andrew Briggs

Thermodynamics at the nanoscale
Dr N. Ares / Professor G. A. D. Briggs

Experimental techniques for manipulating small fluctuating systems, such as qubits, are now mature and a great effort for developing quantum technologies is in place.  These quantum devices are systems that evolve, fluctuate and couple to each other and to the environment. As larger quantum circuits are pushed forward, studying the thermodynamics of small systems becomes crucial.  With an experimentally grounded understanding of thermodynamics at the nanoscale, it will be possible to refine future quantum devices through their fully informed design. There is also the possibility of unique behaviours that would open the way for new technologies, such as new refrigeration and sensing techniques, as well as innovative means of storing energy and powering engines. 

To constitute the simplest and most paradigmatic thermodynamic system, we require a system coupled to a heat bath and a battery. In the proposed platform, the system is a two-level quantum system coupled to a nanomechanical resonator, a vibrating carbon nanotube. The resonator stores and provides mechanical work, playing the role of a battery. A cavity will give access to time-resolved measurements of the “battery” and, therefore, will enable direct measurements of the work exchanges in a nanoscale device.


Also see homepages: Natalia Ares Andrew Briggs

Also see a full listing of New projects available within the Department of Materials.