182 research outputs found
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
Compiler Optimization for Quantum Computing Using Reinforcement Learning
Any quantum computing application, once encoded as a quantum circuit, must be
compiled before being executable on a quantum computer. Similar to classical
compilation, quantum compilation is a sequential process with many compilation
steps and numerous possible optimization passes. Despite the similarities, the
development of compilers for quantum computing is still in its infancy-lacking
mutual consolidation on the best sequence of passes, compatibility,
adaptability, and flexibility. In this work, we take advantage of decades of
classical compiler optimization and propose a reinforcement learning framework
for developing optimized quantum circuit compilation flows. Through distinct
constraints and a unifying interface, the framework supports the combination of
techniques from different compilers and optimization tools in a single
compilation flow. Experimental evaluations show that the proposed framework-set
up with a selection of compilation passes from IBM's Qiskit and Quantinuum's
TKET-significantly outperforms both individual compilers in over 70% of cases
regarding the expected fidelity. The framework is available on GitHub
(https://github.com/cda-tum/MQTPredictor).Comment: 6 pages, 3 figure
QudCom: Towards Quantum Compilation for Qudit Systems
Qudit-based quantum computation offers unique advantages over qubit-based
systems in terms of noise mitigation capabilities as well as algorithmic
complexity improvements. However, the software ecosystem for multi-state
quantum systems is severely limited. In this paper, we highlight a quantum
workflow for describing and compiling qudit systems. We investigate the design
and implementation of a quantum compiler for qudit systems. We also explore
several key theoretical properties of qudit computing as well as efficient
optimization techniques. Finally, we provide demonstrations using physical
quantum computers as well as simulations of the proposed quantum toolchain
Reducing the CNOT count for Clifford+T circuits on NISQ architectures
While mapping a quantum circuit to the physical layer one has to consider the
numerous constraints imposed by the underlying hardware architecture.
Connectivity of the physical qubits is one such constraint that restricts
two-qubit operations such as CNOT to "connected" qubits. SWAP gates can be used
to place the logical qubits on admissible physical qubits, but they entail a
significant increase in CNOT-count, considering the fact that each SWAP gate
can be implemented by 3 CNOT gates.
In this paper we consider the problem of reducing the CNOT-count in
Clifford+T circuits on connectivity constrained architectures such as noisy
intermediate-scale quantum (NISQ) (Preskill, 2018) computing devices. We
"slice" the circuit at the position of Hadamard gates and "build" the
intermediate portions. We investigated two kinds of partitioning - (i) a simple
method of partitioning the gates of the input circuit based on the locality of
H gates and (ii) a second method of partitioning the phase polynomial of the
input circuit. The intermediate {CNOT,T} sub-circuits are synthesized using
Steiner trees, significantly improving on the methods introduced by Nash,
Gheorghiu, Mosca[2020] and Kissinger, de Griend[2019].
We compared the performance of our algorithms while mapping different
benchmark circuits as well as random circuits to some popular architectures
such as 9-qubit square grid, 16-qubit square grid, Rigetti 16-qubit Aspen,
16-qubit IBM QX5 and 20-qubit IBM Tokyo. We found that for both the benchmark
and random circuits our first algorithm that uses the simple slicing technique
dramatically reduces the CNOT-count compared to naively using SWAP gates. Our
second slice-and-build algorithm also performs very well for benchmark
circuits.Comment: 41 pages, 2 figures, 2 tables. Added appendix with example
Verifying Results of the IBM Qiskit Quantum Circuit Compilation Flow
Realizing a conceptual quantum algorithm on an actual physical device
necessitates the algorithm's quantum circuit description to undergo certain
transformations in order to adhere to all constraints imposed by the hardware.
In this regard, the individual high-level circuit components are first
synthesized to the supported low-level gate-set of the quantum computer, before
being mapped to the target's architecture---utilizing several optimizations in
order to improve the compilation result. Specialized tools for this complex
task exist, e.g., IBM's Qiskit, Google's Cirq, Microsoft's QDK, or Rigetti's
Forest. However, to date, the circuits resulting from these tools are hardly
verified, which is mainly due to the immense complexity of checking if two
quantum circuits indeed realize the same functionality. In this paper, we
propose an efficient scheme for quantum circuit equivalence
checking---specialized for verifying results of the IBM Qiskit quantum circuit
compilation flow. To this end, we combine characteristics unique to quantum
computing, e.g., its inherent reversibility, and certain knowledge about the
compilation flow into a dedicated equivalence checking strategy. Experimental
evaluations confirm that the proposed scheme allows to verify even large
circuit instances with tens of thousands of operations within seconds or even
less, whereas state-of-the-art techniques frequently time-out or require
substantially more runtime. A corresponding open source implementation of the
proposed method is publicly available at https://github.com/iic-jku/qcec.Comment: 10 pages, to be published at International Conference on Quantum
Computing and Engineering (QCE20
QContext: Context-Aware Decomposition for Quantum Gates
In this paper we propose QContext, a new compiler structure that incorporates
context-aware and topology-aware decompositions. Because of circuit equivalence
rules and resynthesis, variants of a gate-decomposition template may exist.
QContext exploits the circuit information and the hardware topology to select
the gate variant that increases circuit optimization opportunities. We study
the basis-gate-level context-aware decomposition for Toffoli gates and the
native-gate-level context-aware decomposition for CNOT gates. Our experiments
show that QContext reduces the number of gates as compared with the
state-of-the-art approach, Orchestrated Trios.Comment: 10 page
Phase gadget synthesis for shallow circuits
We give an overview of the circuit optimisation methods used by tket, a compiler system for quantum software developed by Cambridge Quantum Computing Ltd. We focus on a novel technique based around phase gadgets, a family of multi-qubit quantum operations which occur naturally in a wide range of quantum circuits of practical interest. The phase gadgets have a simple presentation in the ZX-calculus, which makes it easy to reason about them. Taking advantage of this, we present an efficient method to translate the phase gadgets back to CNOT gates and single qubit operations suitable for execution on a quantum computer with significant reductions in gate count and circuit depth. We demonstrate the effectiveness of these methods on a quantum chemistry benchmarking set based on variational circuits for ground state estimation of small molecules
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