A PyTorch Library for Quantum Simulation and Quantum Machine Learning

Faster, Scalable, Easy Debugging, Easy Deployment on Real Machine

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đź‘‹ Welcome#

What it does#

Quantum simulation framework based on PyTorch. It supports statevector simulation and pulse simulation (coming soon) on GPUs. It can scale up to the simulation of 30+ qubits with multiple GPUs.

Who will benefit#

Researchers on quantum algorithm design, parameterized quantum circuit training, quantum optimal control, quantum machine learning, quantum neural networks.

Differences from Qiskit/Pennylane#

Dynamic computation graph, automatic gradient computation, fast GPU support, batch model tersorized processing.

News#

  • v0.1.7 Available!

  • Join our Slack for real time support!

  • Welcome to contribute! Please contact us or post in the forum if you want to have new examples implemented by TorchQuantum or any other questions.

  • Qmlsys website goes online: qmlsys.mit.edu and torchquantum.org

Features#

  • Easy construction and simulation of quantum circuits in PyTorch

  • Dynamic computation graph for easy debugging

  • Gradient support via autograd

  • Batch mode inference and training on CPU/GPU

  • Easy deployment on real quantum devices such as IBMQ

  • Easy hybrid classical-quantum model construction

  • (coming soon) pulse-level simulation

Installation#

git clone https://github.com/mit-han-lab/torchquantum.git
cd torchquantum
pip install --editable .

Basic Usage#

import torchquantum as tq
import torchquantum.functional as tqf

qdev = tq.QuantumDevice(n_wires=2, bsz=5, device="cpu", record_op=True) # use device='cuda' for GPU

# use qdev.op
qdev.h(wires=0)
qdev.cnot(wires=[0, 1])

# use tqf
tqf.h(qdev, wires=1)
tqf.x(qdev, wires=1)

# use tq.Operator
op = tq.RX(has_params=True, trainable=True, init_params=0.5)
op(qdev, wires=0)

# print the current state (dynamic computation graph supported)
print(qdev)

# obtain the qasm string
from torchquantum.plugin import op_history2qasm
print(op_history2qasm(qdev.n_wires, qdev.op_history))

# measure the state on z basis
print(tq.measure(qdev, n_shots=1024))

# obtain the expval on a observable by stochastic sampling (doable on simulator and real quantum hardware)
from torchquantum.measurement import expval_joint_sampling
expval_sampling = expval_joint_sampling(qdev, 'ZX', n_shots=1024)
print(expval_sampling)

# obtain the expval on a observable by analytical computation (only doable on classical simulator)
from torchquantum.measurement import expval_joint_analytical
expval = expval_joint_analytical(qdev, 'ZX')
print(expval)

# obtain gradients of expval w.r.t. trainable parameters
expval[0].backward()
print(op.params.grad)

Guide to the examples#

We also prepare many example and tutorials using TorchQuantum.

For beginning level, you may check QNN for MNIST, Quantum Convolution (Quanvolution) and Quantum Kernel Method, and Quantum Regression.

For intermediate level, you may check Amplitude Encoding for MNIST, Clifford gate QNN, Save and Load QNN models, PauliSum Operation, How to convert tq to Qiskit.

For expert, you may check Parameter Shift on-chip Training, VQA Gradient Pruning, VQE, VQA for State Prepration, QAOA (Quantum Approximate Optimization Algorithm).

Usage#

Construct parameterized quantum circuit models as simple as constructing a normal pytorch model.

import torch.nn as nn
import torch.nn.functional as F
import torchquantum as tq
import torchquantum.functional as tqf

class QFCModel(nn.Module):
  def __init__(self):
    super().__init__()
    self.n_wires = 4
    self.measure = tq.MeasureAll(tq.PauliZ)

    self.encoder_gates = [tqf.rx] * 4 + [tqf.ry] * 4 + \
                         [tqf.rz] * 4 + [tqf.rx] * 4
    self.rx0 = tq.RX(has_params=True, trainable=True)
    self.ry0 = tq.RY(has_params=True, trainable=True)
    self.rz0 = tq.RZ(has_params=True, trainable=True)
    self.crx0 = tq.CRX(has_params=True, trainable=True)

  def forward(self, x):
    bsz = x.shape[0]
    # down-sample the image
    x = F.avg_pool2d(x, 6).view(bsz, 16)

    # create a quantum device to run the gates
    qdev = tq.QuantumDevice(n_wires=self.n_wires, bsz=bsz, device=x.device)

    # encode the classical image to quantum domain
    for k, gate in enumerate(self.encoder_gates):
      gate(qdev, wires=k % self.n_wires, params=x[:, k])

    # add some trainable gates (need to instantiate ahead of time)
    self.rx0(qdev, wires=0)
    self.ry0(qdev, wires=1)
    self.rz0(qdev, wires=3)
    self.crx0(qdev, wires=[0, 2])

    # add some more non-parameterized gates (add on-the-fly)
    qdev.h(wires=3)
    qdev.sx(wires=2)
    qdev.cnot(wires=[3, 0])
    qdev.qubitunitary(wires=[1, 2], params=[[1, 0, 0, 0],
                                            [0, 1, 0, 0],
                                            [0, 0, 0, 1j],
                                            [0, 0, -1j, 0]])

    # perform measurement to get expectations (back to classical domain)
    x = self.measure(qdev).reshape(bsz, 2, 2)

    # classification
    x = x.sum(-1).squeeze()
    x = F.log_softmax(x, dim=1)

    return x

VQE Example#

Train a quantum circuit to perform VQE task. Quito quantum computer as in simple_vqe.py script:

cd examples/simple_vqe
python simple_vqe.py

MNIST Example#

Train a quantum circuit to perform MNIST task and deploy on the real IBM Quito quantum computer as in mnist_example.py script:

cd examples/simple_mnist
python mnist_example.py

Files#

File

Description

devices.py

QuantumDevice class which stores the statevector

encoding.py

Encoding layers to encode classical values to quantum domain

functional.py

Quantum gate functions

operators.py

Quantum gate classes

layers.py

Layer templates such as RandomLayer

measure.py

Measurement of quantum states to get classical values

graph.py

Quantum gate graph used in static mode

super_layer.py

Layer templates for SuperCircuits

plugins/qiskit*

Convertors and processors for easy deployment on IBMQ

examples/

More examples for training QML and VQE models

Coding Style#

torchquantum uses pre-commit hooks to ensure Python style consistency and prevent common mistakes in its codebase.

To enable it pre-commit hooks please reproduce:

pip install pre-commit
pre-commit install

Papers using TorchQuantum#

Dependencies#

  • 3.9 >= Python >= 3.7 (Python 3.10 may have the concurrent package issue for Qiskit)

  • PyTorch >= 1.8.0

  • configargparse >= 0.14

  • GPU model training requires NVIDIA GPUs

Contact#

TorchQuantum Forum

Hanrui Wang hanrui@mit.edu

Contributors#

Jiannan Cao, Jessica Ding, Jiai Gu, Song Han, Zhirui Hu, Zirui Li, Zhiding Liang, Pengyu Liu, Yilian Liu, Mohammadreza Tavasoli, Hanrui Wang, Zhepeng Wang, Zhuoyang Ye

Citation#

@inproceedings{hanruiwang2022quantumnas,
    title     = {Quantumnas: Noise-adaptive search for robust quantum circuits},
    author    = {Wang, Hanrui and Ding, Yongshan and Gu, Jiaqi and Li, Zirui and Lin, Yujun and Pan, David Z and Chong, Frederic T and Han, Song},
    booktitle = {The 28th IEEE International Symposium on High-Performance Computer Architecture (HPCA-28)},
    year      = {2022}
}