Solid State Quantum Computing

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Solid State Quantum Computing

• A Presentation for EE240 by
• Sean Feltz
• Aggrey Jacobs
• Raphael Mckirchy
• Michael Pietraszewski
• Mark Tjersland

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Quantum Computers

• Quantum computers are devices that can carry out
  computations using quantum mechanical properties
  such as superposition and entanglement.
• Qubits, quantum bits, are used to described
  states similar to the bit in transistor-based
  computing.
• Quantum computers offer not only an increase in
  speed over traditional computers but allows us to
  solve problems such as factoring as a
  exponentially faster.
• They require very controlled system to prevent
  decoherence of qubits, a process in which an they
  are interrupted by some output influence and
  collapse to their 0 or 1 state, losing all the
  superposition probabilities they once stored.

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Qubits

• Qubits are the superposition of two quantum
  states which represent a 0 and 1 value.
• They can be implemented using any quantum
  property that has two states and is observable,
  such as the spin of electrons.
• Qubits can take advantage of quantum
  entanglement, where the states of two qubits
  depend on each other even though they may be at a
  distance, to perform operations on multiple data
  sets simultaneously
• Qubits will collapse to a 0 or 1 state when
  measured.
• Quantum gates can perform operations on qubits
  similar to transistor based gates performing
  logical operations such as AND on bits.

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Quantum vs. Transistor Computers

• Quantum Computers
• Can use any particle which exhibits quantum
  properties to represent states called qubits
• Qubits can be a superposition of 0 and 1 states
• In order to get a reliable answer, algorithms
  must be carried out multiple times
• Fully functional quantum computers are still many
  years in the future

• Transistor-Based Computers
• Uses electrons to represent states called bits
• Bits only handle a 0 or 1 state
• Very stable, giving expected answer for almost
  every operation with a high degree of accuracy
• Practical using todays technology

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How could Quantum Computing be useful?

• Quantum computing has the potential to make large
  calculations approximately a billion times faster
  than any silicon-based computers.
• In Binary computing one calculation can be made
  at a time, but in Quantum computing millions of
  calculations can be made at once.
• Quantum computing will be able to factor large
  numbers, and they will be useful in decoding and
  encoding secret information by using Shors
  algorithm. Ex internet

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How could it be useful?

• Quantum computing could be useful for running
  simulations of quantum mechanics.
• With the speed of Quantum computing this could
  effect many different areas of science such as
  physics, chemistry, materials science,
  nanotechnology, biology, and medicine. Today all
  of these fields are limited due to the speed of
  conventional computers.
• Finding information in large databases in a
  fraction of the time of conventional computing by
  using Grovers Algorithm.

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Quantum Computing in Solid State

• Considered to be the future of quantum computing
• Has the potential to bring quantum computing to
  homes
• Currently has many issues

Currently, other electronics use the same solid
state technology to function By using solid state
technology the QC could become more
affordable Hasnt become an option yet
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Current Concepts

• One concept is to use quantum dots to contain
  electrons
• This would keep them separated and hold one at a
  time
• Using gates and applied voltages, the electrons
  could attract

• Another Concept is the Kane Computer (shown
  below) its a hybrid of QD and NMR methods

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Pros/Cons to Solid State

• Pros
• Would be cheap(aka. Using Silicon)
• Many manufacturing processes already in place
• Can contain large amounts of qubits

• Cons
• Hasnt worked well as of yet
• Needs to be extremely pure to work
• Unpredictability of system

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Some of the Difficulties with Quantum Computing

• Decoherence - the tendecy of a quantum computer
  to decay from a given quantum state into an
  incoherent state as it interacts or entangles
  with the state of the environment
• Error Correction the answers that the
  operations are only right a percentage of the
  time using current quantum technologies
• Hardware architecture

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Problems Measuring Values

• Quantum mechanics tells us that you cannot
  directly measure the value of a qubit until the
  end of the calculation, this measurement destroys
  the superposition of states, forcing everything
  to become a 0 or 1.
• When the superposition states are lost, no more
  operations can be done on that qubit.

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Recent Accomplishments in Quantum Computing (2005)

• Physicists at the Australian National University
  were able to slow down a laser light pulse to a
  mere 100s of meters per second. The light can
  be captured at this speed and information can be
  mapped onto the light beam using photons. This
  is an important step toward communication within
  a quantum computer and like a conventional
  computer storing memory.
• Physicists at Chalmers University were able to
  measure
• the capacitance of a Josephson junction, a
  technique that
• can be used to measure the states of qubits
  without
• changing their values, which is a constant
  difficulty to be
• overcome. Josephson junctions are widely
  used today in
• many electronics.
• The Austrian Institute of Quantum Optics and
  Quantum
• Information creates the first qubyte from 8
  calcium ions.
• Like a byte in a normal computer, a qubyte
  can be used
• to create a piece of data. Qubytes will be
  much more
• complex because they can be set to many
  states at once
• allowing for much more complex operations.
• University of Michigan creates the first scalable
  quantum computer chip using ion trapping. The
  scalability is the most impressive part, as it
  may allow for up to thousands of ions to be
  trapped and in turn many more qubits.

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Most Recent Accomplishments in Quantum Computing
(2006)

• Researchers at Cambridge University and Toshiba
  have created a device that can consistently
  create pairs of entangled photons. The state of
  one photon can be found by measuring the state of
  the other. These entangled photons can be used
  as a clock in quantum computing and in tracking
  information and making sure it is not
  intercepted.
• Scientists at Oxford were able to confine a qubit
  within a buckyball, limiting its interaction with
  the environment, however not quite to the extent
  needed for quantum computing. By repeatedly
  exposing the qubit to microwaves, they are able
  to reverse interactions between the qubit and the
  environment, creating a type of quantum memory.
• Ohio University scientists discover that light
  shining on quantum dots caused them to transfer
  energy in a consistent pattern. This idea may be
  manipulated for quantum computers to communicate
  using light instead of the conventional
  electricity.
• Physicists at the University of Texas have
  created
• a laser trap that can consistently capture
  and
• count at least 60 atoms. Being able to do
  so now
• brings quantum computing one step closer to
  
• manipulating single atoms or particles that
  will be
• used in creating qubits.

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Sources

• http//www.wired.com/news/technology/0,69033-0.htm
  l
• http//physicsweb.org/articles/news/9/11/13/1
• http//blog.wired.com/gadgets/index.blog?entry_id
  1295520
• http//www.umich.edu/news/index.html?Releases/2005
  /Dec05/r121205b
• http//news.zdnet.com/2100-1009_22-6026098.html
• http//www.admin.ox.ac.uk/po/news/2005-06/jan/04a.
  shtml
• http//news.research.ohiou.edu/news/index.php?item
  264
• http//www.utexas.edu/opa/news/2006/01/physics04.h
  tml