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• 1 MIPS ???? 1016?? ?? ? ??? ?? ?
• ????? 300 ?
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Ex)
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Quantum Information Technology
Key words Superposition, Entanglement,
Uncertainty, Interference
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Ex)
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1???? ?? ????
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????

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Postulates of quantum mechanics(Copenhagen
interpretation)

• (1) Schrodinger equation
• (2) Probability of being at x and t
• (3) Physical quantity operator
• (4) Eigenstate and eigenvalue

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Ex)
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I cannot believe that God plays dice with the
universe.
Dont say God what to do.
VS
Niels Bohr
Albert Einstein
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Schrodingers cat

Erwin Schrodinger
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• Collapse of a superposed state or just our
  ignorance?

• ???(Reality) ??

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??(Entanglement)

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I cannot believe that a cat could
drastically change the state of the moon by
merely looking at it The belief in an external
world independent of the perceiving subject is
the basis of all natural science
Thanks to Einsteins work, physicists have come
to realize that space and time are not absolute
but relative to an observers state of motion. In
quantum theory, we simply take this way of
thinking one step further. Why did Einstein find
it so difficult to accept this natural extension
of his own ideas?
A good joke should not be repeated twice.
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Light polarization
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Quantum Eraser
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I can safely say that nobody understands quantum
mechanics
Richard Feynman
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????? ?? ??? ??? ??? ???, ??? ??? ???? ???? ??.
????? ??? ??? ???? ??.
Murray Gellman
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2???? ????
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• Rolf Landauer
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History (of theoretical QIT)

• 1973 Reversible Computing
• 1982 Quantum Computing
• 1984 Quantum Cryptography
• 1993 Quantum Teleportation

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Charles Bennet
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??

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• ?? ABC DEF (??2)
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• RSA ???? ?????

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Quantum Cryptography(??????)
(1) single photon
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??????(Quantum Cryptography)
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1
0
0
1
1
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Quantum Teleportation
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Quantum Teleportation
?
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Alices Bell Measurement
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??? ???? ? ??.
Benjamin Schumacher
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No cloning theorem
?? ???? ??? ??? ? ??.
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Quantum Communication

• Quantum Cryptography
  Stucki, Gisin, et al. (Switzerland),
  67 km
• New Journal of Physics 4, 1 (2002)
  (http//www.idquantique.com/qkd.html)
• Quantum Teleportation
• Marcikic, Gisin, et al. (Switzerland),
• 55m, 2 Km fiber
• Nature 421, 509 (2003)
• 2003. 4.

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• Quantum computation
• Quantum teleportation
• Quantum cryptography
• Quantum dense coding
• Quantum lithography
• Quantum feedback

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3??????
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History (of quantum computing)

• 1973 Bennett Reversible computing
• 1980 Benioff Quantum system as RC
• 1982 Feynman Quantum computing
• 1985 Deutsch first QC algorithm
• 1994 Shor factorization algorithm
• 1996 Grover search algorithm
• 1997 Implementation of QC by NMR
• 2003 ?

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• Shors factorization algorithm
• QC (logN)2x steps (xltlt1)
• classical computer expN1/3(logN)2/3
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• Grovers search algorithm
• for N data search, QC N1/2 try
• classical computer N/2 try
• ex) if N256 1 MIPS, 1000 year vs. 4 min.
• ???????? ??(?)

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Single qubit operation
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??????

• ?? ????? ?? ???
• N ??? 2N ?? ?? ??
• ?? - ? ??? ??? ?? ???? ??
• ex) ?? ?? ?? ?? (0gt1gt)A(0gt1gt)B
• ?? ?? ?? 1gt2gt 0gtA1gtB1gtA0gtB

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????? (NMR Nuclear Magnetic Resonance)
- ???? ??? ????
1) J. Kim, J.-S. Lee, and S. Lee, Phys. Rev. A
61, 032312 (2000). 2) J. Kim, J.-S. Lee, S. Lee,
and C. Cheong, submitted to Phys. Rev. A
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Requirements for a Quantum Computer (1) qubit
two quantum states with good quantum (2) Set
by measurement or thermal equilibrium ex)
(3) Read (4) Single qubit operation
(addressible) physical addressing or
resonance tech. (5) Interaction (controllable)
well defined and on-off ---------------------
---------------------------------------- (6)
Coherence isolation from environment (and other
qubits) (7) Scalability
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Quantum systems suggested as QC
Atomic and Molecular Ion trap Cavity
QED NMR Molecular magnet N_at_C60(fullerine) BEC Sol
id State Quantum dot Superconductor Si-based QC
Optical Photon Photonic crystal
Electron beam el. floating on liquid He el.
trapped by SAW el. trapped by magnetic field
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• (1) qubit - two states with good quantum
• energy el. floating in LHe
• charge quantum dot
• spin quantum dot, molecular magnet, ion
  trap,
• NMR, Si-based QC
• photon optical QC, cavity QED
• cooper pair superconductor
• fluxoid superconductor

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Requirements for a Quantum Computer (1) qubit
SPIN (2) Set by measurement or thermal
equilibrium ex) (3) Read (4) Single qubit
operation (addressible) physical addressing
or resonance tech. (5) Interaction (controllable)
well defined and on-off (6) Coherence
isolation from environment (and other qubits)
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• (6) Long coherence Isolate qubits
• in vacuum ion trap, el. floating in LHe
• by flying methods using photon,
• els trapped by SAW or
  magnetic field
• in molecule NMR
• in quantum well quantum dot, superconductor
• inside solid Si-based QC

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Requirements for a Quantum Computer (1) qubit
SPIN (2) Set by measurement or thermal
equilibrium ex) (3) Read (4) Single qubit
operation (addressible) ? ??? ??? ??? ???
?? (5) Interaction (controllable) well
defined and on-off (6) Coherence solid state
device
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Ion trap
Qubit - ion spin state Single spin operation -
laser Inertaction - vibration(CM motion)
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Si-based QC

• Qubit nuclear spin of P
• Coherence time at 1.5 K
• - el. spin 103 S
• - n. spin 10 hours
• Reading using resonance
• and hyperfine interaction
• Silicon technology

rf ??
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A A
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Si
P
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Requirements for a Quantum Computer (1) qubit
SPIN (2) Set (3) Read (4) Single qubit
operation (addressible) ? ??? ??? ??? ???
?? (5) Interaction (controllable) well
defined and on-off (6) Coherence solid state
device
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Si-based QC
rf ??

• Interaction RKKY
• Distance between P 10 nm
• Read by SET or MRFM
• hyperfine interaction eng.

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A J A
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Si
P
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Requirements for a Quantum Computer (1) qubit
SPIN (2) Set (3) Read Single spin
detection (4) Single qubit operation
(addressible) ? ??? ??? ??? ??? ?? (5)
Interaction control (6) Coherence solid state
device
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Si-based QC
rf ??
A J A
SET
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Magnetic Resonance Force Microscopy (MRFM)
- Scanning Probe? ??? ?? - ???? ??
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2003.7
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Si-base QC
..100
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0 1 2 3 4 5 6 7.
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Environment
measurement
EM field
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• Conclusion of QC
• Developing QC is the key issue.
• Development of QC depends on nanotechnology (
  spintronics).
• Development of QC requires precise control of
• Reading single spin detection
• Interaction between qubits
• with environment

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Bio- informatics
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control
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nm
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size
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The END