Qubits and Superposition

Just like Qiskit's Hadamard gate, Cirq's cirq.H puts a qubit into an equal superposition, a genuine mix of 0 and 1 until measured.

Simulating without measuring

import cirq

qubit = cirq.LineQubit(0)
circuit = cirq.Circuit()
circuit.append(cirq.H(qubit))

simulator = cirq.Simulator()
result = simulator.simulate(circuit)
print(result.dirac_notation())          # something like 0.71|0> + 0.71|1>
print(abs(result.final_state_vector) ** 2)  # [0.5, 0.5]

• cirq.Simulator() is Cirq's local simulator, .simulate(circuit) runs a circuit without any measurement, returning the exact final quantum state (only possible on a simulator, exactly like Qiskit's Statevector).
• result.dirac_notation() prints the state using physicists' bra-ket notation, |0> and |1> are the two basis states, and the numbers in front are amplitudes.
• result.final_state_vector is the raw list of complex amplitudes, squaring their absolute values (abs(...) ** 2) converts each amplitude into a probability, mirroring Qiskit's state.probabilities().

Measurement still collapses the state

circuit_measured = cirq.Circuit()
circuit_measured.append(cirq.H(qubit))
circuit_measured.append(cirq.measure(qubit, key='result'))

result = simulator.simulate(circuit_measured)
print(result.measurements['result'])  # a single definite outcome, 0 or 1

result.measurements is a dictionary keyed by the measurement keys you assigned with cirq.measure(..., key=...), once a qubit is measured, its superposition is gone, exactly as in Qiskit, the physics doesn't change, only the SDK's syntax does.