9,305 research outputs found
Implementation of a quantum controlled-SWAP gate with photonic circuits
Quantum information science addresses how the processing and transmission of
information are affected by uniquely quantum mechanical phenomena. Combination
of two-qubit gates has been used to realize quantum circuits, however,
scalability is becoming a critical problem. The use of three-qubit gates may
simplify the structure of quantum circuits dramatically. Among them, the
controlled-SWAP (Fredkin) gates are essential since they can be directly
applied to important protocols, e.g., error correction, fingerprinting, and
optimal cloning. Here we report a realization of the Fredkin gate for photonic
qubits. We achieve a fidelity of 0.85 in the computational basis and an output
state fidelity of 0.81 for a 3-photon Greenberger-Horne-Zeilinger state. The
estimated process fidelity of 0.77 indicates that our Fredkin gate can be
applied to various quantum tasks.Comment: 9 pages, 4 figures, Sci. Rep. 7, 45353 (2017
The Qudit ZH-Calculus: Generalised Toffoli+Hadamard and Universality
We introduce the qudit ZH-calculus and show how to generalise all the
phase-free qubit rules to qudits. We prove that for prime dimensions d, the
phase-free qudit ZH-calculus is universal for matrices over the ring
Z[e^2(pi)i/d]. For qubits, there is a strong connection between phase-free
ZH-diagrams and Toffoli+Hadamard circuits, a computationally universal fragment
of quantum circuits. We generalise this connection to qudits, by finding that
the two-qudit |0>-controlled X gate can be used to construct all classical
reversible qudit logic circuits in any odd qudit dimension, which for qubits
requires the three-qubit Toffoli gate. We prove that our construction is
asymptotically optimal up to a logarithmic term. Twenty years after the
celebrated result by Shi proving universality of Toffoli+Hadamard for qubits,
we prove that circuits of |0>-controlled X and Hadamard gates are approximately
universal for qudit quantum computing for any odd prime d, and moreover that
phase-free ZH-diagrams correspond precisely to such circuits allowing
post-selections.Comment: In Proceedings QPL 2023, arXiv:2308.1548
Synthesis and Optimization of Reversible Circuits - A Survey
Reversible logic circuits have been historically motivated by theoretical
research in low-power electronics as well as practical improvement of
bit-manipulation transforms in cryptography and computer graphics. Recently,
reversible circuits have attracted interest as components of quantum
algorithms, as well as in photonic and nano-computing technologies where some
switching devices offer no signal gain. Research in generating reversible logic
distinguishes between circuit synthesis, post-synthesis optimization, and
technology mapping. In this survey, we review algorithmic paradigms ---
search-based, cycle-based, transformation-based, and BDD-based --- as well as
specific algorithms for reversible synthesis, both exact and heuristic. We
conclude the survey by outlining key open challenges in synthesis of reversible
and quantum logic, as well as most common misconceptions.Comment: 34 pages, 15 figures, 2 table
Noise-Adaptive Compiler Mappings for Noisy Intermediate-Scale Quantum Computers
A massive gap exists between current quantum computing (QC) prototypes, and
the size and scale required for many proposed QC algorithms. Current QC
implementations are prone to noise and variability which affect their
reliability, and yet with less than 80 quantum bits (qubits) total, they are
too resource-constrained to implement error correction. The term Noisy
Intermediate-Scale Quantum (NISQ) refers to these current and near-term systems
of 1000 qubits or less. Given NISQ's severe resource constraints, low
reliability, and high variability in physical characteristics such as coherence
time or error rates, it is of pressing importance to map computations onto them
in ways that use resources efficiently and maximize the likelihood of
successful runs.
This paper proposes and evaluates backend compiler approaches to map and
optimize high-level QC programs to execute with high reliability on NISQ
systems with diverse hardware characteristics. Our techniques all start from an
LLVM intermediate representation of the quantum program (such as would be
generated from high-level QC languages like Scaffold) and generate QC
executables runnable on the IBM Q public QC machine. We then use this framework
to implement and evaluate several optimal and heuristic mapping methods. These
methods vary in how they account for the availability of dynamic machine
calibration data, the relative importance of various noise parameters, the
different possible routing strategies, and the relative importance of
compile-time scalability versus runtime success. Using real-system
measurements, we show that fine grained spatial and temporal variations in
hardware parameters can be exploited to obtain an average x (and up to
x) improvement in program success rate over the industry standard IBM
Qiskit compiler.Comment: To appear in ASPLOS'1
Optimized Compilation of Aggregated Instructions for Realistic Quantum Computers
Recent developments in engineering and algorithms have made real-world
applications in quantum computing possible in the near future. Existing quantum
programming languages and compilers use a quantum assembly language composed of
1- and 2-qubit (quantum bit) gates. Quantum compiler frameworks translate this
quantum assembly to electric signals (called control pulses) that implement the
specified computation on specific physical devices. However, there is a
mismatch between the operations defined by the 1- and 2-qubit logical ISA and
their underlying physical implementation, so the current practice of directly
translating logical instructions into control pulses results in inefficient,
high-latency programs. To address this inefficiency, we propose a universal
quantum compilation methodology that aggregates multiple logical operations
into larger units that manipulate up to 10 qubits at a time. Our methodology
then optimizes these aggregates by (1) finding commutative intermediate
operations that result in more efficient schedules and (2) creating custom
control pulses optimized for the aggregate (instead of individual 1- and
2-qubit operations). Compared to the standard gate-based compilation, the
proposed approach realizes a deeper vertical integration of high-level quantum
software and low-level, physical quantum hardware. We evaluate our approach on
important near-term quantum applications on simulations of superconducting
quantum architectures. Our proposed approach provides a mean speedup of
, with a maximum of . Because latency directly affects the
feasibility of quantum computation, our results not only improve performance
but also have the potential to enable quantum computation sooner than otherwise
possible.Comment: 13 pages, to apper in ASPLO
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