100 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
A Synergistic Compilation Workflow for Tackling Crosstalk in Quantum Machines
Near-term quantum systems tend to be noisy. Crosstalk noise has been
recognized as one of several major types of noises in superconducting Noisy
Intermediate-Scale Quantum (NISQ) devices. Crosstalk arises from the concurrent
execution of two-qubit gates on nearby qubits, such as \texttt{CX}. It might
significantly raise the error rate of gates in comparison to running them
individually. Crosstalk can be mitigated through scheduling or hardware machine
tuning. Prior scientific studies, however, manage crosstalk at a really late
phase in the compilation process, usually after hardware mapping is done. It
may miss great opportunities of optimizing algorithm logic, routing, and
crosstalk at the same time. In this paper, we push the envelope by considering
all these factors simultaneously at the very early compilation stage. We
propose a crosstalk-aware quantum program compilation framework called CQC that
can enhance crosstalk mitigation while achieving satisfactory circuit depth.
Moreover, we identify opportunities for translation from intermediate
representation to the circuit for application-specific crosstalk mitigation,
for instance, the \texttt{CX} ladder construction in variational quantum
eigensolvers (VQE). Evaluations through simulation and on real IBM-Q devices
show that our framework can significantly reduce the error rate by up to
6, with only 60\% circuit depth compared to state-of-the-art gate
scheduling approaches. In particular, for VQE, we demonstrate 49\% circuit
depth reduction with 9.6\% fidelity improvement over prior art on the H4
molecule using IBMQ Guadalupe. Our CQC framework will be released on GitHub
Optimal Layout Synthesis for Quantum Computing
Recent years have witnessed the fast development of quantum computing.
Researchers around the world are eager to run larger and larger quantum
algorithms that promise speedups impossible to any classical algorithm.
However, the available quantum computers are still volatile and error-prone.
Thus, layout synthesis, which transforms quantum programs to meet these
hardware limitations, is a crucial step in the realization of quantum
computing. In this paper, we present two synthesizers, one optimal and one
approximate but nearly optimal. Although a few optimal approaches to this
problem have been published, our optimal synthesizer explores a larger solution
space, thus is optimal in a stronger sense. In addition, it reduces time and
space complexity exponentially compared to some leading optimal approaches. The
key to this success is a more efficient spacetime-based variable encoding of
the layout synthesis problem as a mathematical programming problem. By slightly
changing our formulation, we arrive at an approximate synthesizer that is even
more efficient and outperforms some leading heuristic approaches, in terms of
additional gate cost, by up to 100%, and also fidelity by up to 10x on a
comprehensive set of benchmark programs and architectures. For a specific
family of quantum programs named QAOA, which is deemed to be a promising
application for near-term quantum computers, we further adjust the approximate
synthesizer by taking commutation into consideration, achieving up to 75%
reduction in depth and up to 65% reduction in additional cost compared to the
tool used in a leading QAOA study.Comment: to appear in ICCAD'2
Computational Capabilities and Compiler Development for Neutral Atom Quantum Processors: Connecting Tool Developers and Hardware Experts
Neutral Atom Quantum Computing (NAQC) emerges as a promising hardware
platform primarily due to its long coherence times and scalability.
Additionally, NAQC offers computational advantages encompassing potential
long-range connectivity, native multi-qubit gate support, and the ability to
physically rearrange qubits with high fidelity. However, for the successful
operation of a NAQC processor, one additionally requires new software tools to
translate high-level algorithmic descriptions into a hardware executable
representation, taking maximal advantage of the hardware capabilities.
Realizing new software tools requires a close connection between tool
developers and hardware experts to ensure that the corresponding software tools
obey the corresponding physical constraints. This work aims to provide a basis
to establish this connection by investigating the broad spectrum of
capabilities intrinsic to the NAQC platform and its implications on the
compilation process. To this end, we first review the physical background of
NAQC and derive how it affects the overall compilation process by formulating
suitable constraints and figures of merit. We then provide a summary of the
compilation process and discuss currently available software tools in this
overview. Finally, we present selected case studies and employ the discussed
figures of merit to evaluate the different capabilities of NAQC and compare
them between two hardware setups.Comment: 32 pages, 13 figures, 2 table
Demonstration of quantum volume 64 on a superconducting quantum computing system
We improve the quality of quantum circuits on superconducting quantum
computing systems, as measured by the quantum volume, with a combination of
dynamical decoupling, compiler optimizations, shorter two-qubit gates, and
excited state promoted readout. This result shows that the path to larger
quantum volume systems requires the simultaneous increase of coherence, control
gate fidelities, measurement fidelities, and smarter software which takes into
account hardware details, thereby demonstrating the need to continue to
co-design the software and hardware stack for the foreseeable future.Comment: Fixed typo in author list. Added references [38], [49] and [52
Magic-State Functional Units: Mapping and Scheduling Multi-Level Distillation Circuits for Fault-Tolerant Quantum Architectures
Quantum computers have recently made great strides and are on a long-term
path towards useful fault-tolerant computation. A dominant overhead in
fault-tolerant quantum computation is the production of high-fidelity encoded
qubits, called magic states, which enable reliable error-corrected computation.
We present the first detailed designs of hardware functional units that
implement space-time optimized magic-state factories for surface code
error-corrected machines. Interactions among distant qubits require surface
code braids (physical pathways on chip) which must be routed. Magic-state
factories are circuits comprised of a complex set of braids that is more
difficult to route than quantum circuits considered in previous work [1]. This
paper explores the impact of scheduling techniques, such as gate reordering and
qubit renaming, and we propose two novel mapping techniques: braid repulsion
and dipole moment braid rotation. We combine these techniques with graph
partitioning and community detection algorithms, and further introduce a
stitching algorithm for mapping subgraphs onto a physical machine. Our results
show a factor of 5.64 reduction in space-time volume compared to the best-known
previous designs for magic-state factories.Comment: 13 pages, 10 figure
- …