756 research outputs found
Massively parallel quantum computer simulator, eleven years later
A revised version of the massively parallel simulator of a universal quantum
computer, described in this journal eleven years ago, is used to benchmark
various gate-based quantum algorithms on some of the most powerful
supercomputers that exist today. Adaptive encoding of the wave function reduces
the memory requirement by a factor of eight, making it possible to simulate
universal quantum computers with up to 48 qubits on the Sunway TaihuLight and
on the K computer. The simulator exhibits close-to-ideal weak-scaling behavior
on the Sunway TaihuLight,on the K computer, on an IBM Blue Gene/Q, and on Intel
Xeon based clusters, implying that the combination of parallelization and
hardware can track the exponential scaling due to the increasing number of
qubits. Results of executing simple quantum circuits and Shor's factorization
algorithm on quantum computers containing up to 48 qubits are presented.Comment: Substantially rewritten + new data. Published in Computer Physics
Communicatio
Fast simulation of quantum algorithms using circuit optimization
Classical simulators play a major role in the development and benchmark of
quantum algorithms and practically any software framework for quantum
computation provides the option of running the algorithms on simulators.
However, the development of quantum simulators was substantially separated from
the rest of the software frameworks which, instead, focus on usability and
compilation. Here, we demonstrate the advantage of co-developing and
integrating simulators and compilers by proposing a specialized compiler pass
to reduce the simulation time for arbitrary circuits. While the concept is
broadly applicable, we present a concrete implementation based on the Intel
Quantum Simulator, a high-performance distributed simulator. As part of this
work, we extend its implementation with additional functionalities related to
the representation of quantum states. The communication overhead is reduced by
changing the order in which state amplitudes are stored in the distributed
memory, a concept analogous to the distinction between local and global qubits
for distributed Schroedinger-type simulators. We then implement a compiler pass
to exploit the novel functionalities by introducing special instructions
governing data movement as part of the quantum circuit. Those instructions
target unique capabilities of simulators and have no analogue in actual quantum
devices. To quantify the advantage, we compare the time required to simulate
random circuits with and without our optimization. The simulation time is
typically halved
Hybrid Quantum Classical Simulations
We report on two major hybrid applications of quantum computing, namely, the
quantum approximate optimisation algorithm (QAOA) and the variational quantum
eigensolver (VQE). Both are hybrid quantum classical algorithms as they require
incremental communication between a classical central processing unit and a
quantum processing unit to solve a problem. We find that the QAOA scales much
better to larger problems than random guessing, but requires significant
computational resources. In contrast, a coarsely discretised version of quantum
annealing called approximate quantum annealing (AQA) can reach the same
promising scaling behaviour using much less computational resources. For the
VQE, we find reasonable results in approximating the ground state energy of the
Heisenberg model when suitable choices of initial states and parameters are
used. Our design and implementation of a general quasi-dynamical evolution
further improves these results.Comment: This article is a book contribution. The book is freely available at
http://hdl.handle.net/2128/3184
A quantum circuit simulator and its applications on Sunway TaihuLight supercomputer
Classical simulation of quantum computation is vital for verifying quantum
devices and assessing quantum algorithms. We present a new quantum circuit
simulator developed on the Sunway TaihuLight supercomputer. Compared with other
simulators, the present one is distinguished in two aspects. First, our
simulator is more versatile. The simulator consists of three mutually
independent parts to compute the full, partial and single amplitudes of a
quantum state with different methods. It has the function of emulating the
effect of noise and support more kinds of quantum operations. Second, our
simulator is of high efficiency. The simulator is designed in a two-level
parallel structure to be implemented efficiently on the distributed many-core
Sunway TaihuLight supercomputer. Random quantum circuits can be simulated with
40, 75 and 200 qubits on the full, partial and single amplitude, respectively.
As illustrative applications of the simulator, we present a quantum fast
Poisson solver and an algorithm for quantum arithmetic of evaluating
transcendental functions. Our simulator is expected to have broader
applications in developing quantum algorithms in various fields.Comment: 21 pages, 9 figure
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