55,247 research outputs found
Noise in One-Dimensional Measurement-Based Quantum Computing
Measurement-Based Quantum Computing (MBQC) is an alternative to the quantum
circuit model, whereby the computation proceeds via measurements on an
entangled resource state. Noise processes are a major experimental challenge to
the construction of a quantum computer. Here, we investigate how noise
processes affecting physical states affect the performed computation by
considering MBQC on a one-dimensional cluster state. This allows us to break
down the computation in a sequence of building blocks and map physical errors
to logical errors. Next, we extend the Matrix Product State construction to
mixed states (which is known as Matrix Product Operators) and once again map
the effect of physical noise to logical noise acting within the correlation
space. This approach allows us to consider more general errors than the
conventional Pauli errors, and could be used in order to simulate noisy quantum
computation.Comment: 16 page
Holonomic quantum computing in symmetry-protected ground states of spin chains
While solid-state devices offer naturally reliable hardware for modern
classical computers, thus far quantum information processors resemble vacuum
tube computers in being neither reliable nor scalable. Strongly correlated many
body states stabilized in topologically ordered matter offer the possibility of
naturally fault tolerant computing, but are both challenging to engineer and
coherently control and cannot be easily adapted to different physical
platforms. We propose an architecture which achieves some of the robustness
properties of topological models but with a drastically simpler construction.
Quantum information is stored in the symmetry-protected degenerate ground
states of spin-1 chains, while quantum gates are performed by adiabatic
non-Abelian holonomies using only single-site fields and nearest-neighbor
couplings. Gate operations respect the symmetry, and so inherit some protection
from noise and disorder from the symmetry-protected ground states.Comment: 19 pages, 4 figures. v2: published versio
Quantum Computing
Quantum mechanics---the theory describing the fundamental workings of
nature---is famously counterintuitive: it predicts that a particle can be in
two places at the same time, and that two remote particles can be inextricably
and instantaneously linked. These predictions have been the topic of intense
metaphysical debate ever since the theory's inception early last century.
However, supreme predictive power combined with direct experimental observation
of some of these unusual phenomena leave little doubt as to its fundamental
correctness. In fact, without quantum mechanics we could not explain the
workings of a laser, nor indeed how a fridge magnet operates. Over the last
several decades quantum information science has emerged to seek answers to the
question: can we gain some advantage by storing, transmitting and processing
information encoded in systems that exhibit these unique quantum properties?
Today it is understood that the answer is yes. Many research groups around the
world are working towards one of the most ambitious goals humankind has ever
embarked upon: a quantum computer that promises to exponentially improve
computational power for particular tasks. A number of physical systems,
spanning much of modern physics, are being developed for this task---ranging
from single particles of light to superconducting circuits---and it is not yet
clear which, if any, will ultimately prove successful. Here we describe the
latest developments for each of the leading approaches and explain what the
major challenges are for the future.Comment: 26 pages, 7 figures, 291 references. Early draft of Nature 464, 45-53
(4 March 2010). Published version is more up-to-date and has several
corrections, but is half the length with far fewer reference
Layered architecture for quantum computing
We develop a layered quantum computer architecture, which is a systematic
framework for tackling the individual challenges of developing a quantum
computer while constructing a cohesive device design. We discuss many of the
prominent techniques for implementing circuit-model quantum computing and
introduce several new methods, with an emphasis on employing surface code
quantum error correction. In doing so, we propose a new quantum computer
architecture based on optical control of quantum dots. The timescales of
physical hardware operations and logical, error-corrected quantum gates differ
by several orders of magnitude. By dividing functionality into layers, we can
design and analyze subsystems independently, demonstrating the value of our
layered architectural approach. Using this concrete hardware platform, we
provide resource analysis for executing fault-tolerant quantum algorithms for
integer factoring and quantum simulation, finding that the quantum dot
architecture we study could solve such problems on the timescale of days.Comment: 27 pages, 20 figure
Architecture and noise analysis of continuous variable quantum gates using two-dimensional cluster states
Due to its unique scalability potential, continuous variable quantum optics
is a promising platform for large scale quantum computing and quantum
simulation. In particular, very large cluster states with a two-dimensional
topology that are suitable for universal quantum computing and quantum
simulation can be readily generated in a deterministic manner, and routes
towards fault-tolerance via bosonic quantum error-correction are known. In this
article we propose a complete measurement-based quantum computing architecture
for the implementation of a universal set of gates on the recently generated
two-dimensional cluster states [1,2]. We analyze the performance of the various
quantum gates that are executed in these cluster states as well as in other
two-dimensional cluster states (the bilayer-square lattice and quad-rail
lattice cluster states [3,4]) by estimating and minimizing the associated
stochastic noise addition as well as the resulting gate error probability. We
compare the four different states and find that, although they all allow for
universal computation, the quad-rail lattice cluster state performs better than
the other three states which all exhibit similar performance
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