IBMQ Executor

This quantum executor accesses IBM Quantum backends through Pennylane’s "qiskit.ibmq" device. IBMQExecutor introduces thread-based parallelism for circuit execution on the “qiskit.ibmq” device. Note that the more efficient QiskitExecutor is recommended over IBMQExecutor for production use.

1. Installation

The IBMQ executor is not included with base Covalent. To install it, run

pip install covalent[qiskit]

2. Usage Example

Using IBMQExecutor requires specifying an IBM Quantum backend through the backend argument. The ibmqx_token is required if not specified in the configuration (see next section).

import covalent as ct
import pennylane as qml

# IBMQ executor that uses "ibmq_qasm_simulator" (default).
ibmq_qasm = ct.executor.IBMQExecutor()

# IBMQ executor that uses the "ibmq_lima" QPU.
ibmq_lima = ct.executor.IBMQExecutor(
    backend="ibmq_lima",
    ibmqx_token="<token>",
)

@ct.qelectron(executors=[ibmq_qasm, ibmq_lima])
@qml.qnode(qml.device("default.qubit", wires=2, shots=1024), interface="jax")
def circuit(x):
    qml.IQPEmbedding(features=x, wires=[0, 1])
    qml.Hadamard(wires=1)
    return qml.probs(wires=range(2))

As a QElectron, the circuit can be called either normally or asynchronously using circuit.run_later(). With the default "cyclic" selector, circuit calls will alternate between the executors, [ibmq_qasm, ibmq_lima].

A synchronous example is shown below.

>>> print(circuit([0.5, 0.1]))  # ibmq_qasm_simulator

DeviceArray([0.51660156, 0.00097656, 0.4814453 , 0.00097656], dtype=float32)

>>> print(circuit([0.5, 0.1]))  # ibmq_lima

DeviceArray([0.5048828 , 0.00195312, 0.49316406, 0.        ], dtype=float32)

>>> print(circuit([0.5, 0.1]))  # ibmq_qasm_simulator (again)

DeviceArray([0.5097656 , 0.00292969, 0.4873047 , 0.        ], dtype=float32)

Doing this asynchronously:

>>> x = [0.6, -1.57]

>>> # Queue jobs for all three circuit calls simultaneously on IBM Quantum.
>>> # Uses same executor order as above (qasm, lima, qasm, ...).
>>> futs = [circuit.run_later(x) for _ in range(3)]

>>> # Wait for all circuits to finish.
>>> [fut.result() for fut in futs]

[DeviceArray([0.51660156, 0.00097656, 0.4814453 , 0.00097656], dtype=float32),
 DeviceArray([0.5048828 , 0.00195312, 0.49316406, 0.        ], dtype=float32),
 DeviceArray([0.5097656 , 0.00292969, 0.4873047 , 0.        ], dtype=float32)]

3. Overview of Configuration

The IBMQExecutor configuration is found under [qelectron.IBMQExecutor] in the Covalent configuration file.

Config Key	Is Required	Default	Description
backend	Yes	ibm_qasm_simulator	The name of an IBM Quantum system or simulator.
ibmqx_token	Yes/No		An access token obtained from IBM Quantum. Required for non-local execution.
hub	No	ibm-q	Hub name for IBM Quantum.
group	No	open	Group name for IBM Quantum.
project	No	main	Project name for IBM Quantum.

4. Required Cloud Resources

Users must acquire an access token from the IBM Quantum Experience in order to use IBM systems and simulators.

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