Solid state quantum computing in endohedral fullerenes

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Solid state quantum computing in endohedral
fullerenes
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Quantum Information Processing IRC

• Objectives
• The development of novel approaches for the
  controlled generation and manipulation of
  entanglement between two or more qubits.
• The development of methods for efficient transfer
  of quantum information between static and
  propagating qubits.
• These objectives include both theoretical
  analysis of new methods of manipulation and
  transfer between qubits of the same or different
  types, and also their experimental design and
  exploratory implementation.

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Fullerenes
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Atoms in fullerenes
The fullerene cage can encapsulate other species
Er3N_at_C80
N_at_C60
Sc, La, Ce, ... _at_C82
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Bang-bang control
J.J.L. Morton et al., Nature Physics 2, 40-43
(2006)
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Bang-bang control
J.J.L. Morton et al., Nature Physics 2, 40-43
(2006)
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Bang-bang control
J.J.L. Morton et al., Nature Physics 2, 40-43
(2006)
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Bang-bang control
J.J.L. Morton et al., Nature Physics 2, 40-43
(2006)
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Bang-bang control
J.J.L. Morton et al., Nature Physics 2, 40-43
(2006)
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Bang-bang control

• Unlike quantum Zeno, bang-bang control is fully
  deterministic.
• Bang-bang control can be used for control of the
  nuclear spin qubit with speed determined by the
  electron spin manipulation.
• The principle of bang-bang control can be applied
  to other systems with three or more levels.

J.J.L. Morton et al., Nature Physics 2, 40-43
(2006)
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3-D spin arrays
C60-4,4'-methylenedianiline

• before
• after
• functionalization

A.A.R. Watt et al., Chem. Commun., 2006,
1944-1946.
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3-D spin arrays
A.A.R. Watt et al., Chem. Commun., 2006,
1944-1946.
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3-D spin arrays
0.06 G
0.13 G
C60-4,4'-methylenedianiline
C60
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2-D spin arrays
(b) The molecules are sublimed onto a silicon
surface. Melamine forms the vertices and PTCDI
forms the edges of a network that assembles
spontaneously. The open network provides a
template for adsorption of fullerenes.
(c) The pores in the network form nanoscale traps
which capture fullerene molecules and stabilise
heptameric C60 clusters.
(d) Networks can extend over several hundreds of
nanometres.
(a) Component molecules melamine and perylene
tetra-carboxylic di-imide (PTCDI) can be
connected by three hydrogen bonds per molecular
junction.
Theobald et al., Nature 424, 1029 (2003)
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1-D spin arrays

• (a, b) C60_at_DWNTs zigzag
• (c, d) C60_at_SWNT chiral
• (e, f) two-molecule layer

Simulated annealing Hodak and Girifalco Phys Rev
B 67, 075419 (2003)
A.N. Khlobystov et al. Phys. Rev. Lett. 92,
245507 (2004)
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1-D spin arrays
e.g. N_at_C60_at_SWNT
Spin localized inside fullerene
e.g. Sc_at_C82_at_SWNT
Spin localized on fullerene cage
e.g. TEMPO-C60_at_SWNT
Spin localized outside fullerene
TEMPO-C60_at_SWNT
A.A.R. Watt et al., Chem. Commun., 2006,
1944-1946.
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Can you build a quantum computer with carbon?

• Goal
• To engineer a hierarchical molecular
  nanostructure exploiting quantum superposition
  and entanglement
• Achievement
• Two qubit experiments have been demonstrated
  using electron and nuclear spins
• Fullerene molecules can be assembled in 3-D, 2-D
  and 1-D arrays
• We have growing understanding of the interactions
  between endohedral fullerene molecules
• Aspiration
• Bring all these steps together to build a
  molecular QIP device

www.qipirc.org