davelowe

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  • in reply to: Could photonic qubits work? #23404
    davelowe
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    Hi @quan – yes you are quite correct about photons not being interactive – they are very ‘inert’.

    There is an architecture based on photons known as the ‘linear optical quantum computer’. These fall into two major sub-types called ‘KLM protocol’ and ‘boson sampling’. Wikipedia has a good article that summarizes what these are.

    In either case, the photon is used as the physical qubit, and there are three major ways that information can be encoded into them.

    1 .time-bin encoding where the 0 & 1 basis states are ‘early and ‘late’ arrival of a photon; the 2-state quantum mechanical system is ‘time of arrival’
    2. number of photos encoding where the 0 & 1 basis states are ‘no photon’ and ‘single photon’; the 2-state quantum mechanical system is the ‘Fock state’
    3. polarization where the 0 & 1 basis states are ‘horizontal’ and ‘vertical’; the 2-state quantum mechanical system is ‘polarisation’

    These types of hardware can be simple to implement since some just rely on simple optical experimental hardware such as mirrors and beamsplitters. The major downside is the velocity of the photons which means that whatever computation you are wanting to perform needs to be performed in one go. Other hardware implementations, such as trapped ion for example, use the internal state of an atom as a qubit, and these can be trapped in one physical location pretty much indefinitely.  Unfortunately the quantum information degrades over time through a process known as decoherence.

    One interesting crossover design is the CQED or cavity quantum electrodynamics computers where the qubit is an atom trapped in a small mirrored cavity where it can undergo what is known as a Rabi oscillation. This means that the atom energy spontaneously decays and emits a photon which has the qubit information, but this is bounced off a mirror and reabsorbed by the atom and then this process repeats. You can see then that this type of design acts as an interface between trapped atoms and photons.

    So far as I’m aware, no large company is actively building an optical quantum computer but I would like to be proven wrong!

    • This reply was modified 1 year, 2 months ago by davelowe.
    in reply to: A First Introduction to Quantum Computing and Information #22861
    davelowe
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    Thanks Hektor – those are really handy!

    in reply to: test #22571
    davelowe
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    try

    in reply to: Test image insert #8342
    davelowe
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    add a reply

    in reply to: Introduction to optical lattices #6407
    davelowe
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    http://www.optical-lattice.com/ is also a good starting point.

    in reply to: Introduction to Ion Trap Quantum Computing #6006
    davelowe
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    davelowe
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    in reply to: CCS Map #1710
    davelowe
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    These are the categories that match “quantum”:
    Hardware Emerging technologies Quantum technologies
    Hardware Emerging technologies Quantum technologies Single electron devices
    Hardware Emerging technologies Quantum technologies Tunneling devices
    Hardware Emerging technologies Quantum technologies Quantum computation
    Hardware Emerging technologies Quantum technologies Quantum computation Quantum communication and cryptography
    Hardware Emerging technologies Quantum technologies Quantum computation Quantum error correction and fault tolerance
    Hardware Emerging technologies Quantum technologies Quantum dots and cellular automata
    Computing methodologies Modeling and simulation Simulation types and techniques Quantum mechanic simulation
    Theory of computation Computational complexity and cryptography Quantum complexity theory
    Theory of computation Models of computation Quantum computation theory
    Theory of computation Models of computation Quantum computation theory Quantum complexity theory
    Theory of computation Models of computation Quantum computation theory Quantum communication complexity
    Theory of computation Models of computation Quantum computation theory Quantum query complexity
    Theory of computation Models of computation Quantum computation theory Quantum information theory
    Computer systems organization Architectures Other architectures Quantum computing

    in reply to: ACM Classification system #1065
    davelowe
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    PDF of the various categories derived directly from the original webpages.

    This is superseded. See the interactive HTML link instead.

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