16 research outputs found
0.5 Petabyte Simulation of a 45-Qubit Quantum Circuit
Near-term quantum computers will soon reach sizes that are challenging to
directly simulate, even when employing the most powerful supercomputers. Yet,
the ability to simulate these early devices using classical computers is
crucial for calibration, validation, and benchmarking. In order to make use of
the full potential of systems featuring multi- and many-core processors, we use
automatic code generation and optimization of compute kernels, which also
enables performance portability. We apply a scheduling algorithm to quantum
supremacy circuits in order to reduce the required communication and simulate a
45-qubit circuit on the Cori II supercomputer using 8,192 nodes and 0.5
petabytes of memory. To our knowledge, this constitutes the largest quantum
circuit simulation to this date. Our highly-tuned kernels in combination with
the reduced communication requirements allow an improvement in time-to-solution
over state-of-the-art simulations by more than an order of magnitude at every
scale
Quantum Algorithm for Spectral Measurement with a Lower Gate Count
We present two techniques that can greatly reduce the number of gates required to realize an energy measurement, with application to ground state preparation in quantum simulations. The first technique realizes that to prepare the ground state of some Hamiltonian, it is not necessary to implement the time-evolution operator: any unitary operator which is a function of the Hamiltonian will do. We propose one such unitary operator which can be implemented exactly, circumventing any Taylor or Trotter approximation errors. The second technique is tailored to lattice models, and is targeted at reducing the use of generic single-qubit rotations, which are very expensive to produce by standard fault tolerant techniques. In particular, the number of generic single-qubit rotations used by our method scales with the number of parameters in the Hamiltonian, which contrasts with a growth proportional to the lattice size required by other techniques
Quantum Algorithm for Spectral Measurement with a Lower Gate Count
We present two techniques that can greatly reduce the number of gates required to realize an energy measurement, with application to ground state preparation in quantum simulations. The first technique realizes that to prepare the ground state of some Hamiltonian, it is not necessary to implement the time-evolution operator: any unitary operator which is a function of the Hamiltonian will do. We propose one such unitary operator which can be implemented exactly, circumventing any Taylor or Trotter approximation errors. The second technique is tailored to lattice models, and is targeted at reducing the use of generic single-qubit rotations, which are very expensive to produce by standard fault tolerant techniques. In particular, the number of generic single-qubit rotations used by our method scales with the number of parameters in the Hamiltonian, which contrasts with a growth proportional to the lattice size required by other techniques
OpenFermion: The Electronic Structure Package for Quantum Computers
Quantum simulation of chemistry and materials is predicted to be an important
application for both near-term and fault-tolerant quantum devices. However, at
present, developing and studying algorithms for these problems can be difficult
due to the prohibitive amount of domain knowledge required in both the area of
chemistry and quantum algorithms. To help bridge this gap and open the field to
more researchers, we have developed the OpenFermion software package
(www.openfermion.org). OpenFermion is an open-source software library written
largely in Python under an Apache 2.0 license, aimed at enabling the simulation
of fermionic models and quantum chemistry problems on quantum hardware.
Beginning with an interface to common electronic structure packages, it
simplifies the translation between a molecular specification and a quantum
circuit for solving or studying the electronic structure problem on a quantum
computer, minimizing the amount of domain expertise required to enter the
field. The package is designed to be extensible and robust, maintaining high
software standards in documentation and testing. This release paper outlines
the key motivations behind design choices in OpenFermion and discusses some
basic OpenFermion functionality which we believe will aid the community in the
development of better quantum algorithms and tools for this exciting area of
research.Comment: 22 page