127,307 research outputs found
Demonstration of unconditional one-way quantum computations for continuous variables
Quantum computing promises to exploit the laws of quantum mechanics for
processing information in ways fundamentally different from today's classical
computers, leading to unprecedented efficiency. One-way quantum computation,
sometimes referred to as the cluster model of quantum computation, is a very
promising approach to fulfil the capabilities of quantum information
processing. The cluster model is realizable through measurements on a highly
entangled cluster state with no need for controlled unitary evolutions. Here we
demonstrate unconditional one-way quantum computation experiments for
continuous variables using a linear cluster state of four entangled optical
modes. We implement an important set of quantum operations, linear
transformations, in the optical phase space through one-way computation. Though
not sufficient, these are necessary for universal quantum computation over
continuous variables, and in our scheme, in principle, any such linear
transformation can be unconditionally and deterministically applied to
arbitrary single-mode quantum states.Comment: 9 pages, 3 figure
Unifying Quantum Computation with Projective Measurements only and One-Way Quantum Computation
Quantum measurement is universal for quantum computation. Two models for
performing measurement-based quantum computation exist: the one-way quantum
computer was introduced by Briegel and Raussendorf, and quantum computation via
projective measurements only by Nielsen. The more recent development of this
second model is based on state transfers instead of teleportation. From this
development, a finite but approximate quantum universal family of observables
is exhibited, which includes only one two-qubit observable, while others are
one-qubit observables. In this article, an infinite but exact quantum universal
family of observables is proposed, including also only one two-qubit
observable.
The rest of the paper is dedicated to compare these two models of
measurement-based quantum computation, i.e. one-way quantum computation and
quantum computation via projective measurements only. From this comparison,
which was initiated by Cirac and Verstraete, closer and more natural
connections appear between these two models. These close connections lead to a
unified view of measurement-based quantum computation.Comment: 9 pages, submitted to QI 200
Measurement Based Quantum Computation on Fractal Lattices
In this article we extend on work which establishes an analology between
one-way quantum computation and thermodynamics to see how the former can be
performed on fractal lattices. We find fractals lattices of arbitrary dimension
greater than one which do all act as good resources for one-way quantum
computation, and sets of fractal lattices with dimension greater than one all
of which do not. The difference is put down to other topological factors such
as ramification and connectivity. This work adds confidence to the analogy and
highlights new features to what we require for universal resources for one-way
quantum computation
The Measurement Calculus
Measurement-based quantum computation has emerged from the physics community
as a new approach to quantum computation where the notion of measurement is the
main driving force of computation. This is in contrast with the more
traditional circuit model which is based on unitary operations. Among
measurement-based quantum computation methods, the recently introduced one-way
quantum computer stands out as fundamental.
We develop a rigorous mathematical model underlying the one-way quantum
computer and present a concrete syntax and operational semantics for programs,
which we call patterns, and an algebra of these patterns derived from a
denotational semantics. More importantly, we present a calculus for reasoning
locally and compositionally about these patterns.
We present a rewrite theory and prove a general standardization theorem which
allows all patterns to be put in a semantically equivalent standard form.
Standardization has far-reaching consequences: a new physical architecture
based on performing all the entanglement in the beginning, parallelization by
exposing the dependency structure of measurements and expressiveness theorems.
Furthermore we formalize several other measurement-based models:
Teleportation, Phase and Pauli models and present compositional embeddings of
them into and from the one-way model. This allows us to transfer all the theory
we develop for the one-way model to these models. This shows that the framework
we have developed has a general impact on measurement-based computation and is
not just particular to the one-way quantum computer.Comment: 46 pages, 2 figures, Replacement of quant-ph/0412135v1, the new
version also include formalization of several other measurement-based models:
Teleportation, Phase and Pauli models and present compositional embeddings of
them into and from the one-way model. To appear in Journal of AC
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