sghkk / qulacs

Variational Quantum Circuit Simulator for Quantum Computation Research

Qulacs

Qulacs is a python/C++ library for fast simulation of large, noisy, or parametric quantum circuits.

Qulacs is licensed under the MIT license.

Quick Install

pip install qulacs

If you have NVIDIA GPU with CUDA installed try:

pip install qulacs-gpu

Feature

• Fast quantum circuit simulation with parallelized C/C++ backend
• Noisy quantum gate for simulation of NISQ devices
• Parametric quantum gates for variational methods
• Circuit compression for fast simulation
• GPU support for fast simulation
• Many utility functions for research

Performance

• Compared following libraries on January, 2020

Package	Version
Qulacs GPU	0.1.9
Cirq	0.6.0
Qiskit Aer	0.3.4
ProjectQ	0.4.2
qHiPSTER	latest master branch
Python interface of QuEST (PyQuest-cffi)	3.0.0
qsim	latest master branch

Test environment:

• Azure NC6s_v3 (6vcpu / Mem112GiB)
• Intel(R) Xeon(R) CPU E5-2690 v4 @ 2.60GHz
• Tesla V100 PCIE (driver 440.33.01)

What is Benchmarked

for each qubit number N:

• Apply simultaneous random single-qubit Pauli-X rotation

and then repeat:

• Apply CNOT(i,(i+1)%N) for all i in [0..N-1]
• Apply simultaneous random single-qubit Pauli-X rotation

for N times.

Note that measured time include time for create quantum circuit.

Single thread benchmark

Multi thread / GPU benchmark

This benchmark was done with majour quantum circuit simulator with python interface.
Yao is quantum circuit simulator using Julia that is as fast as Qulacs.
Benchmark inculde Yao can be found here.

Requirement

• C++ compiler (gcc or VisualStudio)
  • gcc/g++ >= 7.0.0 (checked in Linux, MacOS, cygwin, MinGW, and WSL)
  • Microsoft VisualStudio C++ 2015 or 2017
• python 2.7 or 3.x
• cmake >= 3.0
• git
• (option) CUDA >= 8.0
• (option) AVX2 support

If your system supports AVX2 instructions, SIMD optimization is automatically enabled. If you want to enable GPU simulator, install qulacs through qulacs-gpu package or build from source.

Qulacs is tested on the following systems.

• Ubuntu 16.04 / 18.04
• MacOS X Sierra
• Windows 10

Install from Source

If you encounter some troubles, see troubleshooting.

Install python libs from source

Install (Multi-thread without GPU)

python setup.py install

Install (Multithread with GPU. CUDA is required)

python setup_gpu.py install

Install (Single-thread without GPU. For launching multiple qulacs processes.)

python setup_singlethread.py install

Uninstall

pip uninstall qulacs

Build C++ and python library

GCC

git clone https://github.com/qulacs/qulacs.git
cd qulacs
./script/build_gcc.sh

When you want to build with GPU, use build_gcc_with_gpu.sh.

MSVC

git clone https://github.com/qulacs/qulacs.git
cd qulacs
script/build_msvc_2017.bat

When you want to build with GPU, use build_msvc_2017_with_gpu.bat. If you use MSVC2015, replace 2017 in file names to 2015.

Tutorial and API document

See the following documents for more detail.

• Python Tutorial
• C++ Tutorial
• Examples
• API document

Sample code

Python

from qulacs import Observable, QuantumCircuit, QuantumState
from qulacs.gate import Y,CNOT,merge

state = QuantumState(3)
state.set_Haar_random_state()

circuit = QuantumCircuit(3)
circuit.add_X_gate(0)
merged_gate = merge(CNOT(0,1),Y(1))
circuit.add_gate(merged_gate)
circuit.add_RX_gate(1,0.5)
circuit.update_quantum_state(state)

observable = Observable(3)
observable.add_operator(2.0, "X 2 Y 1 Z 0")
observable.add_operator(-3.0, "Z 2")
value = observable.get_expectation_value(state)
print(value)

If you want to run it on GPU, install GPU-enabled qulacs and replace QuantumState in the above codes to QuantumStateGpu.

C++

#include <iostream>
#include <cppsim/state.hpp>
#include <cppsim/circuit.hpp>
#include <cppsim/observable.hpp>
#include <cppsim/gate_factory.hpp>
#include <cppsim/gate_merge.hpp>

int main(){
    QuantumState state(3);
    state.set_Haar_random_state();

    QuantumCircuit circuit(3);
    circuit.add_X_gate(0);
    auto merged_gate = gate::merge(gate::CNOT(0,1),gate::Y(1));
    circuit.add_gate(merged_gate);
    circuit.add_RX_gate(1,0.5);
    circuit.update_quantum_state(&state);

    Observable observable(3);
    observable.add_operator(2.0, "X 2 Y 1 Z 0");
    observable.add_operator(-3.0, "Z 2");
    auto value = observable.get_expectation_value(&state);
    std::cout << value << std::endl;
    return 0;
}

Build command for g++:

g++ -O2 -I ./<qulacs_path>/include -L ./<qulacs_path>/lib <your_code>.cpp -fopenmp -lcppsim_static.so

If you want to run it on GPU, include cppsim/state_gpu.hpp and replace QuantumState with QuantumStateGpu.

How to cite

Please cite this GitHub URL: https://github.com/qulacs/qulacs

in bibtex style:

@misc{Qulacs,
title = {{Qulacs}},
year = {2018},
eprint = "https://github.com/qulacs/qulacs"
}