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Implementation languagePython
LicenseApache license

Cirq is an open-source framework for Noisy Intermediate Scale Quantum (NISQ) computers.[1]


Cirq was developed by the Google AI Quantum Team, and the public alpha was announced at the International Workshop on Quantum Software and Quantum Machine Learning on July 18, 2018.[2] A demo by QC Ware showed an implementation of QAOA solving an example of the maximum cut problem being solved on a Cirq simulator.[3]


Quantum programs in Cirq are represented by "Circuit" and "Schedule" where "Circuit" represents a Quantum circuit and "Schedule" represents a Quantum circuit with timing information. [4] The programs can be executed on local simulators. [5]

The following example shows how to create and measure a Bell state in Cirq.

import cirq

# Pick qubits
qubit0 = cirq.GridQubit(0, 0)
qubit1 = cirq.GridQubit(0, 1)

# Create a circuit
circuit = cirq.Circuit.from_ops(
    cirq.CNOT(qubit0, qubit1),
    cirq.measure(qubit0, key='m0'),
    cirq.measure(qubit1, key='m1')

Printing the circuit displays it's diagram

# prints
# (0, 0): ───H───@───M('m0')───
#                │
# (0, 1): ───────X───M('m1')───

Simulating the circuit repeatedly shows that the measurements of the qubits are correlated.

simulator = cirq.Simulator()
result =, repetitions=5)
# prints
# m0=11010
# m1=11010



OpenFermion-Cirq is a library that compiles quantum simulation algorithms to Cirq. [2]


  1. ^ Fingerhuth, Mark; Babej, Tomáš; Wittek, Peter (2018). "Open source software in quantum computing". arXiv:1812.09167.
  2. ^ a b Ho, Alan; Bacon, Dave (2018-06-18). "Announcing Cirq: An Open Source Framework for NISQ Algorithms". Google AI Blog. Google AI Quantum Team. Retrieved 2019-03-06.
  3. ^ "public_demos/ at master · qcware/public_demos · GitHub". 20 July 2018. Retrieved 29 October 2019.
  4. ^ "Cirq Circuits". Cirq Github repository. Google AI Quantum Team. 2019-01-09. Retrieved 2019-03-06.
  5. ^ Google AI Quantum Team (2019-01-09). "Cirq Simulation". Cirq Github repository. quantumlib. Retrieved 2019-03-06.