6,138 research outputs found
QuEST and High Performance Simulation of Quantum Computers
We introduce QuEST, the Quantum Exact Simulation Toolkit, and compare it to
ProjectQ, qHipster and a recent distributed implementation of Quantum++. QuEST
is the first open source, OpenMP and MPI hybridised, GPU accelerated simulator
of universal quantum circuits. Embodied as a C library, it is designed so that
a user's code can be deployed seamlessly to any platform from a laptop to a
supercomputer. QuEST is capable of simulating generic quantum circuits of
general single-qubit gates and multi-qubit controlled gates, on pure and mixed
states, represented as state-vectors and density matrices, and under the
presence of decoherence. Using the ARCUS Phase-B and ARCHER supercomputers, we
benchmark QuEST's simulation of random circuits of up to 38 qubits, distributed
over up to 2048 compute nodes, each with up to 24 cores. We directly compare
QuEST's performance to ProjectQ's on single machines, and discuss the
differences in distribution strategies of QuEST, qHipster and Quantum++. QuEST
shows excellent scaling, both strong and weak, on multicore and distributed
architectures.Comment: 8 pages, 8 figures; fixed typos; updated QuEST URL and fixed typo in
Fig. 4 caption where ProjectQ and QuEST were swapped in speedup subplot
explanation; added explanation of simulation algorithm, updated bibliography;
stressed technical novelty of QuEST; mentioned new density matrix suppor
Quantum Analogue Computing
We briefly review what a quantum computer is, what it promises to do for us,
and why it is so hard to build one. Among the first applications anticipated to
bear fruit is quantum simulation of quantum systems. While most quantum
computation is an extension of classical digital computation, quantum
simulation differs fundamentally in how the data is encoded in the quantum
computer. To perform a quantum simulation, the Hilbert space of the system to
be simulated is mapped directly onto the Hilbert space of the (logical) qubits
in the quantum computer. This type of direct correspondence is how data is
encoded in a classical analogue computer. There is no binary encoding, and
increasing precision becomes exponentially costly: an extra bit of precision
doubles the size of the computer. This has important consequences for both the
precision and error correction requirements of quantum simulation, and
significant open questions remain about its practicality. It also means that
the quantum version of analogue computers, continuous variable quantum
computers (CVQC) becomes an equally efficient architecture for quantum
simulation. Lessons from past use of classical analogue computers can help us
to build better quantum simulators in future.Comment: 10 pages, to appear in the Visions 2010 issue of Phil. Trans. Roy.
Soc.
Massive Parallel Quantum Computer Simulator
We describe portable software to simulate universal quantum computers on
massive parallel computers. We illustrate the use of the simulation software by
running various quantum algorithms on different computer architectures, such as
a IBM BlueGene/L, a IBM Regatta p690+, a Hitachi SR11000/J1, a Cray X1E, a SGI
Altix 3700 and clusters of PCs running Windows XP. We study the performance of
the software by simulating quantum computers containing up to 36 qubits, using
up to 4096 processors and up to 1 TB of memory. Our results demonstrate that
the simulator exhibits nearly ideal scaling as a function of the number of
processors and suggest that the simulation software described in this paper may
also serve as benchmark for testing high-end parallel computers.Comment: To appear in Comp. Phys. Com
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