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The magnetic moments of nuclei, atoms and molecules in condensed matter can exhibit strongly quantum behaviour, with discrete energy levels and weak coupling to other degrees of freedom. We study the dynamics of these systems, principally using magnetic resonance, to establish

i) how best to exploit spins in condensed matter for quantum information applications;
ii) the environment of the spin, which can tell us about materials properties, molecular structures, conformation changes, and relaxation mechanisms;
iii) the interaction of spins with other excitations, to allow detection of magnetic resonance through optical or transport phenomena;
iv) and more!

Electron spin ensemble based multimode quantum memory
Dr. A. Ardavan *, Professor G.A.D. Briggs
Ensembles of electron spin could be used as the media for quantum memory by utilizing the principle of holographic information storage. Multiple spatial phase modes are created by applying magnetic field gradient to the spin ensembles, in which multiple units of information are stored. The use of pulsed magnetic field gradients allows us to get access to the stored information selectively. This type of multimode quantum memory, in combination with superconducting qubit and cavity, could be used to develop a hybrid model of quantum computer. (*Clarendon Laboratory, Department of Physics)

Studying silicon solar cells by electrically-detected magnetic resonance
V. Lang, Dr J.D. Murphy, Dr. J.J.L. Morton
Silicon solar cells account for more than 80% of the world market. Their efficiency is partly limited by recombination of charge carriers at defects in the material. We are using the technique of electrically-detected magnetic resonance (EDMR) to study recombination at oxide precipitates, which can form during cooling of multicrystalline silicon ingots. EDMR allows us to identify the specific types of defect responsible for spin-dependent recombination, such as Pb0 or Pb1 dangling bonds in the case of oxide precipitates. This information cannot be found from conventional techniques for solar cell characterisation such as quasi-steady-state photoconductance measurements. (* also of MEMC Electronic Materials Inc.)

Endohedral Fullerenes for Quantum Information Processing
Dr. K. Porfyrakis, Dr. A.M. Khlobystov*, Dr. A. Ardavan**, Professor G.A.D. Briggs
One of the most remarkably robust examples of an unpaired electron spin within a molecule is that of a nitrogen atom trapped inside a spherical fullerene (termed N@C60). We have measured the coherence time of a qubit encoded within this electron spin system and performed single qubit operations using pulsed electron paramagnetic resonance (EPR). We are investigating the synthesis of several types of endohedral fullerene dimers including directly-bonded and oxygen-bridged dimers. These multi-qubit systems will then be characterised by EPR. We shall study the ability to control qubit interactions through the inter-fullerene bridge, and move on to investigate larger qubit arrays. (*University of Nottingham; **Clarendon Laboratory, Department of Physics)

3 public active projects

• 2011
  • Electron spin ensemble strongly coupled to a three-dimensional microwave cavity
    E Abe, H Wu, A Ardavan, JJL Morton App Phys Lett in press (2011) arXiv:1106.0507
  • Electron spin coherence exceeding seconds in high purity silicon
    AM Tyryshkin, S Tojo, JJL Morton, H Riemann, NV Abrosimov, P Becker, H-J Pohl, T Schenkel, MLW Thewalt, KM Itoh, SA Lyon arXiv:1105.3772   (2011)
  • Electrically detected magnetic resonance of neutral donors interacting with a two-dimensional electron gas
    CC Lo, V Lang, RE George, JJL Morton, AM Tyryshkin, SA Lyon, J Bokor, T Schenkel Phys Rev Lett   106 207601 (2011)
  • An amplified single NV centre sensor
    M Schaffry, EM Gauger, JJL Morton, SC Benjamin arXiv:1104.0214     (2011)
  • Violation of a Leggett-Garg inequality with a finite temperature ensemble
    GC Knee, S Simmons, EM Gauger, JJL Morton, H Riemann, NV Abrosimov, P Becker, H-J Pohl, KM Itoh, MLW Thewalt, GAD Briggs, SC Benjamin arXiv:1104.0238   (2011)
  • Coherent state transfer between an electron- and nuclear spin in 15N@C60
    RM Brown, AM Tyryshkin, K Porfyrakis, EM Gauger, BW Lovett, A Ardavan, SA Lyon, GAD Briggs and JJL Morton Phys Rev Lett 106 110504 (2011)
  • Electrically detected magnetic resonance in a W-band microwave cavity
    V Lang, CC Lo, RE George, SA Lyon, J Bokor, T Schenkel, A Ardavan and JJL Morton Rev Sci Instrum 82 034704 (2011)
  • Entanglement in a Solid State Spin Ensemble
    S Simmons, RM Brown, H Riemann, NV Abrosimov, P Becker, H-J Pohl, MLW Thewalt, KM Itoh and JJL Morton Nature 470 69 (2011)
  • Hybrid Solid-State Qubits: The Powerful Role of Electron Spins
    JJL Morton and BW Lovett Annual Review of Condensed Matter 2 189 (2011)
  • Quantum coherence and entanglement in the avian compass
    E Rieper, E Gauger, JJL Morton, SC Benjamin, V Vedral Phys Rev Lett 106 040503 (2011)
• 2010
  • EPR investigation of purified catalyst-free single-walled carbon nanotubes
    M Zaka, Y Ito, H Wang, W Yan, A Robertson, Y Wu, M Rummeli, D Staunton, T Hashimoto, JJL Morton, A Ardavan, GAD Briggs, JH Warner ACS Nano in press (2010)
  • Ensemble based quantum metrology
    M Schaffry, EM Gauger, JJL Morton, J Fitzsimons, SC Benjamin, BW Lovett Phys Rev A 82 042114 (2010)
  • High cooperativity coupling of electron-spin ensembles to superconducting cavities
    DI Schuster, AP Sears, E Ginossar, L DiCarlo, L Frunzio, JJL Morton, H Wu, GAD Briggs, RJ Schoelkopf Phys Rev Lett105 140501 (2010)
  • Storage of multiple coherent microwave excitations in an electron spin ensemble
    H Wu, RE George, A Ardavan, JH Wesenberg, K Mølmer, DI Schuster, RJ Schoelkopf, KM Itoh, JJL Morton, GAD Briggs Phys Rev Lett105 140503 (2010)
    
    • Reviewed (together with Schuster et al. above) in...
      Towards superconductor-spin ensemble hybrid quantum systems T Duty Physics 3 80 (2010), and
      Quantum computing: Quantum RAM M Blencowe Nature 468 44 (2010)
  • Electron spin coherence of phosphorus donors in silicon: Effect of environmental nuclei
    E Abe, AM Tyryshkin, S Tojo, JJL Morton, WM Witzel, A Fujimoto, JW Ager, EE Haller, J Isoya, SA Lyon, MLW Thewalt and KM Itoh Phys Rev B82 121201(R) (2010)
  • Magnetic field sensors using 13-spin cat states
    S Simmons, JA Jones, SD Karlen, A Ardavan, JJL Morton Phys Rev A 82 022330 (2010)
  • A cyclic porphyrin trimer as a receptor for fullerenes
    G Gil-Ramirez, SD Karlen, A Shundo, K Porfyrakis, Y Ito, GAD Briggs, JJL Morton and HL Anderson Org Lett 12 3544 (2010)
  • Electron paramagnetic resonance study of ErSc2NC80
    R Rahman, A Tiwari, G Dantelle, JJL Morton, K Porfyrakis, A Ardavan, K-P Dinse and GAD Briggs arXiv:1004.3912 (2010)
  • Electron spin coherence and electron nuclear double resonance of Bi donors in natural Si
    RE George, W Witzel, H Riemann, NV Abrosimov, N Notzel, MLW Thewalt and JJL Morton Phys Rev Lett 105 067601 (2010)
  • Electron spin coherence in metallofullerenes: Y, Sc and La@C82
    RM Brown, Y Ito, J Warner, A Ardavan, H Shinohara, GAD Briggs and JJL Morton Phys Rev B 82 033410 (2010)
  • Controlling intermolecular spin interactions of La@C82 in empty fullerene matrices
    Y Ito, JH Warner, RM Brown, M Zaka, R Pfeiffer, T Aono, N Izumi, H Okimoto, JJL Morton, A Ardavan, H Shinohara, H Kuzmany, H Peterlik and GAD Briggs Phys Chem Chem Phys 12 1618 (2010)
  • Exchange interactions of spin-active metallofullerenes in solid-state carbon networks
    M Zaka, JH Warner, Y Ito, JJL Morton, MH Rümmeli, T Pichler, A Ardavan, H Shinohara, GAD Briggs Phys Rev B 81 075424 (2010)
  • Entangling remote nuclear spins linked by a chromophore
    M Schaffry, V Filidou, SD Karlen, EM Gauger, SC Benjamin, HL Anderson, A Ardavan, GAD Briggs, K Maeda, KB Henbest, F Giustino, JJL Morton, BW Lovett Phys Rev Lett 104 200501 (2010)
• 2009
  • A silicon-based cluster state quantum computer
    JJL Morton arxiv.org/0905.4008 (2009)
  • Quantum computing with an electron spin ensemble
    JH Wesenberg, A Ardavan, GAD Briggs, JJL Morton, RJ Schoelkopf, DI Schuster, K Mølmer Phys Rev Lett 103 070502 (2009)
  • Magnetic field sensing beyond the standard quantum limit using 10-spin NOON states
    JA Jones, SD Karlen, J Fitzsimons, A Ardavan, SC Benjamin, GAD Briggs and JJL Morton,
    Science 324 1166 (2009)
• 2008
  • Solid state quantum memory using the 31P nuclear spin
    JJL Morton, AM Tyryshkin, RM Brown, S Shankar, BW Lovett, A Ardavan, T Schenkel, EE Haller, JW Ager and SA Lyon, Nature 455 1085 (2008)
  • Switchable ErSc2N rotor within a C80 fullerene cage
    JJL Morton, A Tiwari, G Dantelle, K Porfyrakis, A Ardavan and GAD Briggs, Phys Rev Lett 101 013002 (2008)
  • Photoisomerisation of a fullerene dimer,
    J Zhang, K Porfyrakis, JJL Morton, MR Sambrook, J Harmer, L Xiao, A Ardavan and GAD Briggs, J Phys Chem C 112 2802 (2008)
  • Nuclear relaxation effects in Davies ENDOR variants,
    JJL Morton, NS Lees, BM Hoffman and S Stoll, J Mag Res 191 315 (2008)
• 2007
  • Environmental effects on electron spin relaxation in N@C60,
    JJL Morton, AM Tyryshkin, A Ardavan, K Porfyrakis, SA Lyon and GAD Briggs, Phys Rev B 76 085418 (2007)
  • Will spin-relaxation times in molecular magnets permit quantum information processing?,
    A Ardavan, O Rival, JJL Morton, SJ Blundell, AM Tyryshkin, GA Timco and REP Winnpenny, Phys Rev Lett 98 057201 (2007)
    
    • Reviewed in Molecular magnets: A long-lasting phase W Wernsdorfer Nature Materials 6 174 (2007)
• 2006
  • The effects of a pyrrolidine functional group on the magnetic properties of N@C60,
    J Zhang, JJL Morton, MR Sambrook, K Porfyrakis, A Ardavan and GAD Briggs, Chem Phys Lett 432 523-527 (2006)
  • Diamond wedding for spin couple,
    JJL Morton Nature Physics 2 365-366 (2006)
  • The N@C60 nuclear spin qubit: Bang-bang decoupling and ultrafast phase gates,
    JJL Morton, AM Tyryshkin, A Ardavan, SC Benjamin, K Porfyrakis, SA Lyon and GAD Briggs, Physica Status Solidi B 243 3028-3031 (2006)
  • Photoluminescence, Magneto-PL and PLE of the trimetallic nitride template fullerene Er3N@C80,
    MAG Jones, JJL Morton, RA Taylor, A Ardavan and GAD Briggs, Physica Status Solidi B 243 3037-3041 (2006)
  • Davies ENDOR revisited: Enhanced sensitivity and nuclear spin relaxation,
    AM Tyryshkin, JJL Morton, A Ardavan and SA Lyon, J Chem Phys 124 234508 (2006)
  • Coherence of spin qubits in silicon,
    AM Tyryshkin, JJL Morton, SC Benjamin, A Ardavan, GAD Briggs, J. W. Ager and SA Lyon, J Phys Cond Mat 18 S783-S794 (2006)
  • Towards a fullerene-based quantum computer,
    SC Benjamin, A Ardavan, GAD Briggs, DA Britz, D Gunlycke, J Jefferson, MAG Jones, DF Leigh, BW Lovett, AN Khlobystov, SA Lyon, JJL Morton, K Porfyrakis, MR Sambrook and AM Tyryshkin, J Phys Cond Mat 18 S867-S883 (2006)
  • Synthesis, isolation, and reactivity of the first endohedral fullerene epoxide N@C60,
    MAG Jones, DA Britz, JJL Morton, AN Khlobystov, K Porfyrakis, A Ardavan, and GAD Briggs, Phys Chem Chem Phys 8 2083 (2006)
  • Brokered graph state quantum computing,
    SC Benjamin, DE Browne, J Fitzsimons and JJL Morton, New J Phys 8 141 (2006)
  • Electron spin relaxation of N@C60 in CS2,
    JJL Morton, AM Tyryshkin, A Ardavan, K Porfyrakis, SA Lyon and GAD Briggs, J Chem Phys 124 014508 (2006)
  • Bang-bang control of fullerene qubits using ultra-fast phase gates,
    JJL Morton, AM Tyryshkin, A Ardavan, SC Benjamin, K Porfyrakis, SA Lyon and GAD Briggs, Nature Physics 2 40 (2006)
• 2005
  • High-fidelity single qubit operations using pulsed EPR,
    JJL Morton, AM Tyryshkin, A Ardavan, K Porfyrakis, SA Lyon and GAD Briggs, Phys Rev Lett 95 200501 (2005)
  • Measuring errors in single qubit rotations by pulsed electron paramagnetic resonance,
    JJL Morton, AM Tyryshkin, A Ardavan, K Porfyrakis, SA Lyon and GAD Briggs, Phys Rev A 71 012332 (2005)
  • A new mechanism for electron spin echo envelope modulation,
    JJL Morton, AM Tyryshkin, A Ardavan, K Porfyrakis, SA Lyon and GAD Briggs, J Chem Phys 122 174504 (2005)
  • Inserting fullerene dimers into carbon nanotubes,
    K Porfyrakis, AN Khlobystov, DA Britz, JJL Morton, A Ardavan, M Kanai, TJS Dennis and GAD Briggs, AIP Conf Proc 723 255 (2005)

Quantum dynamics of electron and nuclear spins
JJL Morton / A Ardavan (Department of Physics)

Magnetic domains, each consisting of vast numbers of magnetic atoms, have  been used for decades for information storage, for example in hard disk  drives. New models for computing have been put forth in which information  is encoded at a much deeper level, within the spin of individual nuclei,  atoms and molecules, and calculations performed through the interactions  between spins. The nature of this information inherits the quantum  mechanical properties of the spin states, such as superposition, allowing  certain computations to take place at dramatically faster rates than in  conventional computers.

We study the quantum dynamics of electron and nuclear spin systems, principally using magnetic resonance, to establish i) how best to exploit  spins in condensed matter for quantum information applications; ii) the  environment of the spin, which can tell us about materials properties,  molecular structures, conformation changes, and relaxation mechanisms;  iii) the interaction of spins with other excitations, to allow detection  of magnetic resonance through optical or transport phenomena; iv) ...and  much more!

This research is highly interdisciplinary and includes the development of novel instrumentation and techniques for the coherent manipulation of electron and nuclear spin states. There are extensive opportunities for international travel and collaboration.

Also see homepages: John Morton

Quantum photonics and spintronics of colour centres in diamond
Dr Jason Smith and Dr John Morton

Diamond colour centres have demonstrated exquisite properties as single photon sources and quantum spin registers that operate even at room temperature, providing great opportunities for quantum communications and information technologies. This project will involve using optical microscopy, spectroscopy, and spin resonance techniques to characterise the underlying physics and properties of single colour centres, including the well established nitrogen-vacancy defect, and the '532' centre from which we have recently seen the first single photon emission. Principal collaborations are with Element Six Ltd and the Diamond Trading Company.

Also see homepages: John Morton Jason Smith

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