DMP meeting litreview April 8, 2003 Vincent Conrad

1
DMP meeting lit-reviewApril 8, 2003Vincent
Conrad
Sources xxx.lanl.gov /quant.ph /cond-mat ww
w.vjquantuminfo.org
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Entanglement Purification for Quantum Computation
Authors W. Dur, H,J,Briegel Date February 13,
2003 Reference PRL Volume 90, Number 6

• Interesting bits
• This shows that thresh-holds for fault-tolerant
  QCing depends solely on single system operations
  if one is working in d dimensional systems (where
  8 lt d lt 32).
• This allows for an inter-qubit error rate of up
  to 2/3.
• great news for a few qubit type II -ish
  SSQC

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Dressed Qubits
Interesting bits The idea is to find a
transformation that takes one from a nice
theoretical basis to a real experimental basis
without any error. Ie Find the dressing
transformation V such that This removes
errors without any encoding overhead. The paper
shows it being implemented for the elimination
of -off resonant transitions in multi-level
systems -Inherent spin induced anisotropy that
accompanies the Heisenberg interaction in many
spin-based QCs.
Authors L.A. Wu, D.A. Lidar Date 21 Mar
2003 Reference quant-ph/0303129 v2
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A Method for Modeling Decoherence on a Quantum
Information Processor
Authors G. Teklemariam, E.M.
Fortunato, C.C.Lopez, J.P.Paz, T.F.Havel, D.G.
Cory Date March 18, 2003 Reference quant-ph/03
03115 v1

• Interesting bits
• Gives an overview of Zureks description of
  decoherence.
• Discusses modeling a full QM environment by
  giving a local QM environment random classical
  kicks.
• models this for a few qubits on a classical
  computer.
• argues that this can be implemented on
  current NMR QCs
• I thought it would be interesting for first
  applications for small SSQC array.

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Quantum Algorithms for Lowest Weight Paths and
Spanning Trees in Complete Graphs

• Interesting bits
• Gives examples of techniques for going from a
  classical algorithm to a quantum algorithm.
• Didnt get it much though because not familiar
  with notation.
• example Dijkstras algorithm.
• This finds shortest path between two points in a
  waited function.
• S ? V0, l(v0) ? 0
• for v ? V S do
• (2.a) l(v) ? n(v0,v)
• (3) while S ? V do
• (3.a) find w ? V S such that l(w) is
  minimal
• (3.b) S? S Ü w
• (3.c) for v ? V S do
• (3.c.1) l(v) ? min (l(v),l(w)n(w,v))

Authors Mark Heiligam Date March 20,
2003 Reference quant-ph/0303131 v1
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Synchronized Pulse Control of Decoherence
Authors Chikako Uchiyama Date March 24,
2003 Reference quant-ph/0303144 v1
Interesting bits Didnt understand this paper,
but thought it might be of interest to anyone
looking at decoherence times and methods of
controlling them. Maybe we could send pulses
down the control gates?
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Quantum Oscillations in Two Coupled Charge Qubits
Authors Yu. A. Pashkin, T.Yamamoto, O.Astafiev,
Y. Nakamura, D.V. Averin, J.S. Tsai Date 20 Feb
2003 Reference Nature Vol 421 p 823
Interesting bits This is the Nakamura
experiment but with 2 cooper-pair qubits.
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Practical Design and Simulation of Si based
Quantum-dot Qubits
Authors Mark Friesen, Paul Rugheimer, Donlad E.
Savage, Max G. Lagally, D. W. van der
Weide, Robert Joynt Mark A Eriksson Date 11
March 2003 Reference PRB 67, 121301(R)
Interesting bits Discusses Si-Ge architecture,
with full 3D electrostatics and Hamiltonian
solved via exact diagonalisation in the envelope
approximation. Simulates a 4 qubit structure to
investigate scalabilty. Discusses error levels
related to gate voltages.
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Novel Interaction Induced Oscillations in
Correlated Electron Transport
Authors F. Claro, J.F. Weisz, S.
Curilef Date 27 March 2003 Reference cond-mat/
0303595 v1
Interesting bits Simulations show the
electron-electron interaction produces a new
kind of oscillation in the drift velocity of
electron moving along a chain. Thought it might
be interesting for charge-qubit cellular
automata.
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Papers Discussed

• Entanglement Purification for Quantum Computation
• W. Dur, H,J,Briegel
• PRL Volume 90,
• Number 6
• Dressed Qubits
• L.A. Wu, D.A. Lidar
• quant-ph/0303129 v2
• A Method for Modeling Decoherence on a Quantum
  Information Processor
• G. Teklemariam, E.M. Fortunato, C.C.Lopez,
  J.P.Paz, T.F.Havel, D.G. Cory
• quant-ph/0303115 v1
• Quantum Algorithms for Lowest Weight Paths and
  Spanning Trees in Complete Graphs
• Mark Heiligam
• quant-ph/0303131 v1
• Synchronized Pulse Control of Decoherence
• Chikako Uchiyama