148 research outputs found
Software Pauli Tracking for Quantum Computation
The realisation of large-scale quantum computing is no longer simply a
hardware question. The rapid development of quantum technology has resulted in
dozens of control and programming problems that should be directed towards the
classical computer science and engineering community. One such problem is known
as Pauli tracking. Methods for implementing quantum algorithms that are
compatible with crucial error correction technology utilise extensive quantum
teleportation protocols. These protocols are intrinsically probabilistic and
result in correction operators that occur as byproducts of teleportation. These
byproduct operators do not need to be corrected in the quantum hardware itself.
Instead, byproduct operators are tracked through the circuit and output results
reinterpreted. This tracking is routinely ignored in quantum information as it
is assumed that tracking algorithms will eventually be developed. In this work
we help fill this gap and present an algorithm for tracking byproduct operators
through a quantum computation. We formulate this work based on quantum gate
sets that are compatible with all major forms of quantum error correction and
demonstrate the completeness of the algorithm.Comment: 5 Pages, 1 figure, Accepted for Design, Automation and Test In Europe
(DATE'2014
Synthesis of Topological Quantum Circuits
Topological quantum computing has recently proven itself to be a very
powerful model when considering large- scale, fully error corrected quantum
architectures. In addition to its robust nature under hardware errors, it is a
software driven method of error corrected computation, with the hardware
responsible for only creating a generic quantum resource (the topological
lattice). Computation in this scheme is achieved by the geometric manipulation
of holes (defects) within the lattice. Interactions between logical qubits
(quantum gate operations) are implemented by using particular arrangements of
the defects, such as braids and junctions. We demonstrate that junction-based
topological quantum gates allow highly regular and structured implementation of
large CNOT (controlled-not) gate networks, which ultimately form the basis of
the error corrected primitives that must be used for an error corrected
algorithm. We present a number of heuristics to optimise the area of the
resulting structures and therefore the number of the required hardware
resources.Comment: 7 Pages, 10 Figures, 1 Tabl
Quantum computation on a 19-qubit wide 2d nearest neighbour qubit array
In this paper, we explore the relationship between the width of a qubit
lattice constrained in one dimension and physical thresholds for scalable,
fault-tolerant quantum computation. To circumvent the traditionally low
thresholds of small fixed-width arrays, we deliberately engineer an error bias
at the lowest level of encoding using the surface code. We then address this
engineered bias at a higher level of encoding using a lattice-surgery surface
code bus that exploits this bias, or a repetition code to make logical qubits
with unbiased errors out of biased surface code qubits. Arbitrarily low error
rates can then be reached by further concatenating with other codes, such as
Steane [[7,1,3]] code and the [[15,7,3]] CSS code. This enables a scalable
fixed-width quantum computing architecture on a square qubit lattice that is
only 19 qubits wide, given physical qubits with an error rate of . This potentially eases engineering issues in systems with fine qubit
pitches, such as quantum dots in silicon or gallium arsenide.Comment: 34 pages, 19 figure
Compilation of algorithm-specific graph states for quantum circuits
We present a quantum circuit compiler that prepares an algorithm-specific
graph state from quantum circuits described in high level languages, such as
Cirq and Q#. The computation can then be implemented using a series of
non-Pauli measurements on this graph state. By compiling the graph state
directly instead of starting with a standard lattice cluster state and
preparing it over the course of the computation, we are able to better
understand the resource costs involved and eliminate wasteful Pauli
measurements on the actual quantum device. Access to this algorithm-specific
graph state also allows for optimisation over locally equivalent graph states
to implement the same quantum circuit. The compiler presented here finds ready
application in measurement based quantum computing, NISQ devices and logical
level compilation for fault tolereant implementations
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Neutrino interactions in the deuterium-neon 14 foot double bubble chamber
We propose to study the interactions of high energy neutrinos in the 14 foot bubble chamber. The target chamber to be filled with Deuterium and the surrounding region filled with nearly pure Neon. An exposure of one million pictures is requested, in order to map out the s and t dependences of the basic interaction in which neutrinos participate
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