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QuSimPy

Maintained by adamisntdead

Qusim.py is a toy multi-qubit quantum computer simulator, written in 150 lines of python

PythonAGPL-3.0
QuSimPy illustration

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Simulators

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724

Last pushed

Jun 4, 2021Updated 5y ago

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2

Quickstart

Get running in a few lines.

Quickstart
from QuSim import QuantumRegister

#############################################
#                 Introduction              #
#############################################
# Here Will Be A Few Example of Different
# Quantum States / Algorithms, So You Can
# Get A Feel For How The Module Works, and  
# Some Algorithmic Ideas


#############################################
#            Quantum Measurement            #
#############################################
# This experiment will prepare 2 states, of a
# Single qubit, and of 5 qubits, and will just
# Measure them

OneQubit = QuantumRegister(1)  # New Quantum Register of 1 Qubit
print('One Qubit: ' + OneQubit.measure())  # Should Print 'One Qubit: 0'

FiveQubits = QuantumRegister(5)  # New Quantum Register of 5 Qubits
# Should Print 'Five Qubits: 00000'
print('Five Qubits: ' + FiveQubits.measure())

#############################################
#                 Swap 2 Qubits             #
#############################################
# Here, We Will Apply a Pauli-X Gate / NOT Gate
# To the first qubit, and then after the algorithm,
# it will be swapped to the second qubit.

Swap = QuantumRegister(2)  # New Quantum Register of 2 qubits
Swap.applyGate('X', 1)  # Apply The NOT Gate. If Measured Now, it should be 10

# Start the swap algorithm
Swap.applyGate('CNOT', 1, 2)
Swap.applyGate('H', 1)
Swap.applyGate('H', 2)
Swap.applyGate('CNOT', 1, 2)
Swap.applyGate('H', 1)
Swap.applyGate('H', 2)
Swap.applyGate('CNOT', 1, 2)
# End the swap algorithm

print('SWAP: |' + Swap.measure() + '>')  # Measure the State, Should be 01

#############################################
#               Fair Coin Flip              #
#############################################
# Shown in this 'Experiment', is a so called 'Fair Coin Flip',
# Where a state will be prepared, that has an equal chance of
# Flipping to Each Possible State. to do this, the Hadamard
# Gate will be used.

# New Quantum Register of 1 Qubit (As a coin has only 2 states)
FairCoinFlip = QuantumRegister(1)
# If measured at this point, it should be |0>

# Apply the hadamard gate, now theres an even chance of measuring 0 or 1
FairCoinFlip.applyGate('H', 1)

# Now, the state will be measured, flipping the state to
# either 0 or 1. If its 0, we will say "Heads", or if its
# 1, we will say "Tails"
FairCoinFlipAnswer = FairCoinFlip.measure()  # Now its flipped, so we can test
if FairCoinFlipAnswer == '0':
    print('FairCoinFlip: Heads')
elif FairCoinFlipAnswer == '1':
    print('FairCoinFlip: Tails')

#############################################
#             CNOT Gate                     #
#############################################
# In this experiment, 4 states will be prepared, {00, 01, 10, 11}
# And then the same CNOT Gate will be run on them,
# To Show The Effects of the CNOT. The Target Qubit will be 2, and the control 1

# New Quantum Register of 2 Qubits, done 4 times.
# If any are measured at this time, the result will be 00
ZeroZero = QuantumRegister(2)
ZeroOne = QuantumRegister(2)
OneZero = QuantumRegister(2)
OneOne = QuantumRegister(2)

# Now prepare Each Into The State Based On Their Name
# ZeroZero Will be left, as thats the first state anyway
ZeroOne.applyGate('X', 2)
OneZero.applyGate('X', 1)
OneOne.applyGate('X', 1)
OneOne.applyGate('X', 2)

# Now, a CNOT Will Be Applied To Each.
ZeroZero.applyGate('CNOT', 1, 2)
ZeroOne.applyGate('CNOT', 1, 2)
OneZero.applyGate('CNOT', 1, 2)
OneOne.applyGate('CNOT', 1, 2)

# Print the results.
print('CNOT on 00: |' + ZeroZero.measure() + '>')
print('CNOT on 01: |' + ZeroOne.measure() + '>')
print('CNOT on 10: |' + OneZero.measure() + '>')
print('CNOT on 11: |' + OneOne.measure() + '>')

What it is

QuSimPy is maintained by adamisntdead and sits in the Simulators lane of the open-source quantum map.

Qusim.py is a toy multi-qubit quantum computer simulator, written in 150 lines of python

Last verified by Qtangl generator on May 27, 2026

Who it's for

Developers and researchers who need to test ideas locally before running on hardware or who want to compare simulation strategies.

What you can build or learn

  • Benchmark how different simulation methods trade accuracy for runtime.
  • Inspect circuit behavior, noise assumptions, or state evolution offline.
  • Choose the right simulator for a debugging, teaching, or research workflow.

License

AGPL-3.0

SPDX identifier detected from the repository metadata or license files.

Repository README

Preview from the project README.

Rendered as Markdown inside a scrollable preview. Long READMEs stay contained; expand or open on GitHub for the full document.

~596 words · about 3 min readOpen on GitHub

QuSim.py

Build Status

Qusim.py is a toy multi-qubit quantum computer simulator, written in 150 lines of python

This code makes it easy for you to see how a quantum computer computes by following the linear algebra!

from QuSim import QuantumRegister

#############################################
#                 Introduction              #
#############################################
# Here Will Be A Few Example of Different
# Quantum States / Algorithms, So You Can
# Get A Feel For How The Module Works, and  
# Some Algorithmic Ideas

#############################################
#            Quantum Measurement            #
#############################################
# This experiment will prepare 2 states, of a
# Single qubit, and of 5 qubits, and will just
# Measure them

OneQubit = QuantumRegister(1)  # New Quantum Register of 1 Qubit
print('One Qubit: ' + OneQubit.measure())  # Should Print 'One Qubit: 0'

FiveQubits = QuantumRegister(5)  # New Quantum Register of 5 Qubits
# Should Print 'Five Qubits: 00000'
print('Five Qubits: ' + FiveQubits.measure())

#############################################
#                 Swap 2 Qubits             #
#############################################
# Here, We Will Apply a Pauli-X Gate / NOT Gate
# To the first qubit, and then after the algorithm,
# it will be swapped to the second qubit.

Swap = QuantumRegister(2)  # New Quantum Register of 2 qubits
Swap.applyGate('X', 1)  # Apply The NOT Gate. If Measured Now, it should be 10

# Start the swap algorithm
Swap.applyGate('CNOT', 1, 2)
Swap.applyGate('H', 1)
Swap.applyGate('H', 2)
Swap.applyGate('CNOT', 1, 2)
Swap.applyGate('H', 1)
Swap.applyGate('H', 2)
Swap.applyGate('CNOT', 1, 2)
# End the swap algorithm

print('SWAP: |' + Swap.measure() + '>')  # Measure the State, Should be 01

#############################################
#               Fair Coin Flip              #
#############################################
# Shown in this 'Experiment', is a so called 'Fair Coin Flip',
# Where a state will be prepared, that has an equal chance of
# Flipping to Each Possible State. to do this, the Hadamard
# Gate will be used.

# New Quantum Register of 1 Qubit (As a coin has only 2 states)
FairCoinFlip = QuantumRegister(1)
# If measured at this point, it should be |0>

# Apply the hadamard gate, now theres an even chance of measuring 0 or 1
FairCoinFlip.applyGate('H', 1)

# Now, the state will be measured, flipping the state to
# either 0 or 1. If its 0, we will say "Heads", or if its
# 1, we will say "Tails"
FairCoinFlipAnswer = FairCoinFlip.measure()  # Now its flipped, so we can test
if FairCoinFlipAnswer == '0':
    print('FairCoinFlip: Heads')
elif FairCoinFlipAnswer == '1':
    print('FairCoinFlip: Tails')

#############################################
#             CNOT Gate                     #
#############################################
# In this experiment, 4 states will be prepared, {00, 01, 10, 11}
# And then the same CNOT Gate will be run on them,
# To Show The Effects of the CNOT. The Target Qubit will be 2, and the control 1

# New Quantum Register of 2 Qubits, done 4 times.
# If any are measured at this time, the result will be 00
ZeroZero = QuantumRegister(2)
ZeroOne = QuantumRegister(2)
OneZero = QuantumRegister(2)
OneOne = QuantumRegister(2)

# Now prepare Each Into The State Based On Their Name
# ZeroZero Will be left, as thats the first state anyway
ZeroOne.applyGate('X', 2)
OneZero.applyGate('X', 1)
OneOne.applyGate('X', 1)
OneOne.applyGate('X', 2)

# Now, a CNOT Will Be Applied To Each.
ZeroZero.applyGate('CNOT', 1, 2)
ZeroOne.applyGate('CNOT', 1, 2)
OneZero.applyGate('CNOT', 1, 2)
OneOne.applyGate('CNOT', 1, 2)

# Print the results.
print('CNOT on 00: |' + ZeroZero.measure() + '>')
print('CNOT on 01: |' + ZeroOne.measure() + '>')
print('CNOT on 10: |' + OneZero.measure() + '>')
print('CNOT on 11: |' + OneOne.measure() + '>')

Largely based on the code from corbett/QuantumComputing.

If you are interested in a efficient, high performance, hardware accelerated quantum computer simulator written in Rust, please check out QCGPU

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