qiskit.circuit.QuantumCircuit.measure

QuantumCircuit.measure(qubit, cbit)

Measure a quantum bit (qubit) in the Z basis into a classical bit (cbit).

When a quantum state is measured, a qubit is projected in the computational (Pauli Z) basis to either \(\lvert 0 \rangle\) or \(\lvert 1 \rangle\). The classical bit cbit indicates the result of that projection as a 0 or a 1 respectively. This operation is non-reversible.

Parâmetros

• qubit (Union[Qubit, QuantumRegister, int, slice, Sequence[Union[Qubit, int]]]) – qubit(s) to measure.

• cbit (Union[Clbit, ClassicalRegister, int, slice, Sequence[Union[Clbit, int]]]) – classical bit(s) to place the measurement result(s) in.

Retorno

handle to the added instructions.

Tipo de retorno

qiskit.circuit.InstructionSet

Levanta

CircuitError – if arguments have bad format.

Examples

In this example, a qubit is measured and the result of that measurement is stored in the classical bit (usually expressed in diagrams as a double line):

from qiskit import QuantumCircuit
circuit = QuantumCircuit(1, 1)
circuit.h(0)
circuit.measure(0, 0)
circuit.draw()

     ┌───┐┌─┐
  q: ┤ H ├┤M├
     └───┘└╥┘
c: 1/══════╩═
           0

It is possible to call measure with lists of qubits and cbits as a shortcut for one-to-one measurement. These two forms produce identical results:

circuit = QuantumCircuit(2, 2)
circuit.measure([0,1], [0,1])

circuit = QuantumCircuit(2, 2)
circuit.measure(0, 0)
circuit.measure(1, 1)

Instead of lists, you can use QuantumRegister and ClassicalRegister under the same logic.

from qiskit import QuantumCircuit, QuantumRegister, ClassicalRegister
qreg = QuantumRegister(2, "qreg")
creg = ClassicalRegister(2, "creg")
circuit = QuantumCircuit(qreg, creg)
circuit.measure(qreg, creg)

This is equivalent to:

circuit = QuantumCircuit(qreg, creg)
circuit.measure(qreg[0], creg[0])
circuit.measure(qreg[1], creg[1])