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Qiskit 0.14 release notes

0.14.0

Terra 0.11.0

Prelude

The 0.11.0 release includes several new features and bug fixes. The biggest change for this release is the addition of the pulse scheduler. This allows users to define their quantum program as a QuantumCircuit and then map it to the underlying pulse instructions that will control the quantum hardware to implement the circuit.

New Features

  • Added 5 new commands to easily retrieve user-specific data from BackendProperties: gate_property, gate_error, gate_length, qubit_property, t1, t2, readout_error and frequency. They return the specific values of backend properties. For example:

    from qiskit.test.mock import FakeOurense
backend = FakeOurense()
properties = backend.properties()
 
gate_property = properties.gate_property('u1')
gate_error = properties.gate_error('u1', 0)
gate_length = properties.gate_length('u1', 0)
qubit_0_property = properties.qubit_property(0)
t1_time_0 = properties.t1(0)
t2_time_0 = properties.t2(0)
readout_error_0 = properties.readout_error(0)
frequency_0 = properties.frequency(0)

  • Added method Instruction.is_parameterized() to check if an instruction object is parameterized. This method returns True if and only if instruction has a ParameterExpression or Parameter object for one of its params.

  • Added a new analysis pass Layout2qDistance. This pass allows to “score” a layout selection, once property_set['layout'] is set. The score will be the sum of distances for each two-qubit gate in the circuit, when they are not directly connected. This scoring does not consider direction in the coupling map. The lower the number, the better the layout selection is.

    For example, consider a linear coupling map [0]--[2]--[1] and the following circuit:

    qr = QuantumRegister(2, 'qr')
circuit = QuantumCircuit(qr)
circuit.cx(qr[0], qr[1])

    If the layout is {qr[0]:0, qr[1]:1}, Layout2qDistance will set property_set['layout_score'] = 1. If the layout is {qr[0]:0, qr[1]:2}, then the result is property_set['layout_score'] = 0. The lower the score, the better.

  • Added qiskit.QuantumCircuit.cnot as an alias for the cx method of QuantumCircuit. The names cnot and cx are often used interchangeably now the cx method can be called with either name.

  • Added qiskit.QuantumCircuit.toffoli as an alias for the ccx method of QuantumCircuit. The names toffoli and ccx are often used interchangeably now the ccx method can be called with either name.

  • Added qiskit.QuantumCircuit.fredkin as an alias for the cswap method of QuantumCircuit. The names fredkin and cswap are often used interchangeably now the cswap method can be called with either name.

  • The latex output mode for qiskit.visualization.circuit_drawer() and the qiskit.circuit.QuantumCircuit.draw() method now has a mode to passthrough raw latex from gate labels and parameters. The syntax for doing this mirrors matplotlib’s mathtext mode syntax. Any portion of a label string between a pair of ‘$’ characters will be treated as raw latex and passed directly into the generated output latex. This can be leveraged to add more advanced formatting to circuit diagrams generated with the latex drawer.

    Prior to this release all gate labels were run through a utf8 -> latex conversion to make sure that the output latex would compile the string as expected. This is still what happens for all portions of a label outside the ‘$’ pair. Also if you want to use a dollar sign in your label make sure you escape it in the label string (ie '\$').

    You can mix and match this passthrough with the utf8 -> latex conversion to create the exact label you want, for example:

    from qiskit import circuit
circ = circuit.QuantumCircuit(2)
circ.h([0, 1])
circ.append(circuit.Gate(name='α_gate', num_qubits=1, params=[0]), [0])
circ.append(circuit.Gate(name='α_gate$_2$', num_qubits=1, params=[0]), [1])
circ.append(circuit.Gate(name='\$α\$_gate', num_qubits=1, params=[0]), [1])
circ.draw(output='latex')

    will now render the first custom gate’s label as α_gate, the second will be α_gate with a 2 subscript, and the last custom gate’s label will be $α$_gate.

  • Add ControlledGate class for representing controlled gates. Controlled gate instances are created with the control(n) method of Gate objects where n represents the number of controls. The control qubits come before the controlled qubits in the new gate. For example:

    from qiskit import QuantumCircuit
from qiskit.extensions import HGate
hgate = HGate()
circ = QuantumCircuit(4)
circ.append(hgate.control(3), [0, 1, 2, 3])
print(circ)

    generates:

    q_0: |0>──■──
          │
q_1: |0>──■──
          │
q_2: |0>──■──
        ┌─┴─┐
q_3: |0>┤ H ├
        └───┘

  • Allowed values of meas_level parameters and fields can now be a member from the IntEnum class qiskit.qobj.utils.MeasLevel. This can be used when calling execute (or anywhere else meas_level is specified) with a pulse experiment. For example:

    from qiskit import QuantumCircuit, transpile, schedule, execute
from qiskit.test.mock import FakeOpenPulse2Q
from qiskit.qobj.utils import MeasLevel, MeasReturnType
 
backend = FakeOpenPulse2Q()
qc = QuantumCircuit(2, 2)
qc.h(0)
qc.cx(0,1)
qc_transpiled = transpile(qc, backend)
sched = schedule(qc_transpiled, backend)
execute(sched, backend, meas_level=MeasLevel.CLASSIFIED)

    In this above example, meas_level=MeasLevel.CLASSIFIED and meas_level=2 can be used interchangably now.

  • A new layout selector based on constraint solving is included. CSPLayout models the problem of finding a layout as a constraint problem and uses recursive backtracking to solve it.

    cmap16 = CouplingMap(FakeRueschlikon().configuration().coupling_map)
 
qr = QuantumRegister(5, 'q')
circuit = QuantumCircuit(qr)
circuit.cx(qr[0], qr[1])
circuit.cx(qr[0], qr[2])
circuit.cx(qr[0], qr[3])
 
pm = PassManager(CSPLayout(cmap16))
circuit_after = pm.run(circuit)
print(pm.property_set['layout'])
    Layout({
1: Qubit(QuantumRegister(5, 'q'), 1),
2: Qubit(QuantumRegister(5, 'q'), 0),
3: Qubit(QuantumRegister(5, 'q'), 3),
4: Qubit(QuantumRegister(5, 'q'), 4),
15: Qubit(QuantumRegister(5, 'q'), 2)
})

    The parameter CSPLayout(...,strict_direction=True) is more restrictive but it will guarantee there is no need of running CXDirection after.

    pm = PassManager(CSPLayout(cmap16, strict_direction=True))
circuit_after = pm.run(circuit)
print(pm.property_set['layout'])
    Layout({
8: Qubit(QuantumRegister(5, 'q'), 4),
11: Qubit(QuantumRegister(5, 'q'), 3),
5: Qubit(QuantumRegister(5, 'q'), 1),
6: Qubit(QuantumRegister(5, 'q'), 0),
7: Qubit(QuantumRegister(5, 'q'), 2)
})

    If the constraint system is not solvable, the layout property is not set.

    circuit.cx(qr[0], qr[4])
pm = PassManager(CSPLayout(cmap16))
circuit_after = pm.run(circuit)
print(pm.property_set['layout'])
    None

  • PulseBackendConfiguration (accessed normally as backend.configuration()) has been extended with useful methods to explore its data and the functionality that exists in PulseChannelSpec. PulseChannelSpec will be deprecated in the future. For example:

    backend = provider.get_backend(backend_name)
config = backend.configuration()
q0_drive = config.drive(0)  # or, DriveChannel(0)
q0_meas = config.measure(0)  # MeasureChannel(0)
q0_acquire = config.acquire(0)  # AcquireChannel(0)
config.hamiltonian  # Returns a dictionary with hamiltonian info
config.sample_rate()  # New method which returns 1 / dt

  • PulseDefaults (accessed normally as backend.defaults()) has an attribute, circuit_instruction_map which has the methods of CmdDef. The new circuit_instruction_map is an InstructionScheduleMap object with three new functions beyond what CmdDef had:

    • qubit_instructions(qubits) returns the operations defined for the qubits
    • assert_has(instruction, qubits) raises an error if the op isn’t defined
    • remove(instruction, qubits) like pop, but doesn’t require parameters

    There are some differences from the CmdDef:

    • __init__ takes no arguments
    • cmds and cmd_qubits are deprecated and replaced with instructions and qubits_with_instruction

    Example:

    backend = provider.get_backend(backend_name)
inst_map = backend.defaults().circuit_instruction_map
qubit = inst_map.qubits_with_instruction('u3')[0]
x_gate = inst_map.get('u3', qubit, P0=np.pi, P1=0, P2=np.pi)
pulse_schedule = x_gate(DriveChannel(qubit))

  • A new kwarg parameter, show_framechange_channels to optionally disable displaying channels with only framechange instructions in pulse visualizations was added to the qiskit.visualization.pulse_drawer() function and qiskit.pulse.Schedule.draw() method. When this new kwarg is set to False the output pulse schedule visualization will not include any channels that only include frame changes.

    For example:

    from qiskit.pulse import *
from qiskit.pulse import library as pulse_lib
 
gp0 = pulse_lib.gaussian(duration=20, amp=1.0, sigma=1.0)
sched = Schedule()
channel_a = DriveChannel(0)
channel_b = DriveChannel(1)
sched += Play(gp0, channel_a)
sched = sched.insert(60, ShiftPhase(-1.57, channel_a))
sched = sched.insert(30, ShiftPhase(-1.50, channel_b))
sched = sched.insert(70, ShiftPhase(1.50, channel_b))
 
sched.draw(show_framechange_channels=False)

  • A new utility function qiskit.result.marginal_counts() is added which allows marginalization of the counts over some indices of interest. This is useful when more qubits are measured than needed, and one wishes to get the observation counts for some subset of them only.

  • When passmanager.run(...) is invoked with more than one circuit, the transpilation of these circuits will run in parallel.

  • PassManagers can now be sliced to create a new PassManager containing a subset of passes using the square bracket operator. This allow running or drawing a portion of the PassManager for easier testing and visualization. For example let’s try to draw the first 3 passes of a PassManager pm, or run just the second pass on our circuit:

    pm[0:4].draw()
circuit2 = pm[1].run(circuit)

    Also now, PassManagers can be created by adding two PassManagers or by directly adding a pass/list of passes to a PassManager.

    pm = pm1[0] + pm2[1:3]
pm += [setLayout, unroller]

  • A basic scheduler module has now been added to Qiskit. The scheduler schedules an input transpiled QuantumCircuit into a pulse Schedule. The scheduler accepts as input a Schedule and either a pulse Backend, or a CmdDef which relates circuit Instruction objects on specific qubits to pulse Schedules and a meas_map which determines which measurements must occur together.

    Scheduling example:

    from qiskit import QuantumCircuit, transpile, schedule
from qiskit.test.mock import FakeOpenPulse2Q
 
backend = FakeOpenPulse2Q()
qc = QuantumCircuit(2, 2)
qc.h(0)
qc.cx(0,1)
qc_transpiled = transpile(qc, backend)
schedule(qc_transpiled, backend)

    The scheduler currently supports two scheduling policies, as_late_as_possible (alap) and as_soon_as_possible (asap), which respectively schedule pulse instructions to occur as late as possible or as soon as possible across qubits in a circuit. The scheduling policy may be selected with the input argument method, for example:

    schedule(qc_transpiled, backend, method='alap')

    It is easy to use a pulse Schedule within a QuantumCircuit by mapping it to a custom circuit instruction such as a gate which may be used in a QuantumCircuit. To do this, first, define the custom gate and then add an entry into the CmdDef for the gate, for each qubit that the gate will be applied to. The gate can then be used in the QuantumCircuit. At scheduling time the gate will be mapped to the underlying pulse schedule. Using this technique allows easy integration with preexisting qiskit modules such as Ignis.

    For example:

    from qiskit import pulse, circuit, schedule
from qiskit.pulse import pulse_lib
 
custom_cmd_def = pulse.CmdDef()
 
# create custom gate
custom_gate = circuit.Gate(name='custom_gate', num_qubits=1, params=[])
 
# define schedule for custom gate
custom_schedule = pulse.Schedule()
custom_schedule += pulse_lib.gaussian(20, 1.0, 10)(pulse.DriveChannel)
 
# add schedule to custom gate with same name
custom_cmd_def.add('custom_gate', (0,), custom_schedule)
 
# use custom gate in a circuit
custom_qc = circuit.QuantumCircuit(1)
custom_qc.append(custom_gate, qargs=[0])
 
# schedule the custom gate
schedule(custom_qc, cmd_def=custom_cmd_def, meas_map=[[0]])

Known Issues

  • The feature for transpiling in parallel when passmanager.run(...) is invoked with more than one circuit is not supported under Windows. See #2988 for more details.

Upgrade Notes

  • The qiskit.pulse.channels.SystemTopology class was used as a helper class for PulseChannelSpec. It has been removed since with the deprecation of PulseChannelSpec and changes to BackendConfiguration make it unnecessary.
  • The previously deprecated representation of qubits and classical bits as tuple, which was deprecated in the 0.9 release, has been removed. The use of Qubit and Clbit objects is the new way to represent qubits and classical bits.
  • The previously deprecated representation of the basis set as single string has been removed. A list of strings is the new preferred way.
  • The method BaseModel.as_dict, which was deprecated in the 0.9 release, has been removed in favor of the method BaseModel.to_dict.
  • In PulseDefaults (accessed normally as backend.defaults()), qubit_freq_est and meas_freq_est are now returned in Hz rather than GHz. This means the new return values are 1e9 * their previous value.
  • dill was added as a requirement. This is needed to enable running passmanager.run() in parallel for more than one circuit.
  • The previously deprecated gate UBase, which was deprecated in the 0.9 release, has been removed. The gate U3Gate should be used instead.
  • The previously deprecated gate CXBase, which was deprecated in the 0.9 release, has been removed. The gate CnotGate should be used instead.
  • The instruction snapshot used to implicitly convert the label parameter to string. That conversion has been removed and an error is raised if a string is not provided.
  • The previously deprecated gate U0Gate, which was deprecated in the 0.9 release, has been removed. The gate IdGate should be used instead to insert delays.

Deprecation Notes

  • The qiskit.pulse.CmdDef class has been deprecated. Instead you should use the qiskit.pulse.InstructionScheduleMap. The InstructionScheduleMap object for a pulse enabled system can be accessed at backend.defaults().instruction_schedules.

  • PulseChannelSpec is being deprecated. Use BackendConfiguration instead. The backend configuration is accessed normally as backend.configuration(). The config has been extended with most of the functionality of PulseChannelSpec, with some modifications as follows, where 0 is an exemplary qubit index:

    pulse_spec.drives[0]   -> config.drive(0)
pulse_spec.measures[0] -> config.measure(0)
pulse_spec.acquires[0] -> config.acquire(0)
pulse_spec.controls[0] -> config.control(0)

    Now, if there is an attempt to get a channel for a qubit which does not exist for the device, a BackendConfigurationError will be raised with a helpful explanation.

    The methods memoryslots and registerslots of the PulseChannelSpec have not been migrated to the backend configuration. These classical resources are not restrained by the physical configuration of a backend system. Please instantiate them directly:

    pulse_spec.memoryslots[0] -> MemorySlot(0)
pulse_spec.registerslots[0] -> RegisterSlot(0)

    The qubits method is not migrated to backend configuration. The result of qubits can be built as such:

    [q for q in range(backend.configuration().n_qubits)]

  • Qubit within pulse.channels has been deprecated. They should not be used. It is possible to obtain channel <=> qubit mappings through the BackendConfiguration (or backend.configuration()).

  • The function qiskit.visualization.circuit_drawer.qx_color_scheme() has been deprecated. This function is no longer used internally and doesn’t reflect the current IBM QX style. If you were using this function to generate a style dict locally you must save the output from it and use that dictionary directly.

  • The Exception TranspilerAccessError has been deprecated. An alternative function TranspilerError can be used instead to provide the same functionality. This alternative function provides the exact same functionality but with greater generality.

  • Buffers in Pulse are deprecated. If a nonzero buffer is supplied, a warning will be issued with a reminder to use a Delay instead. Other options would include adding samples to a pulse instruction which are (0.+0.j) or setting the start time of the next pulse to schedule.duration + buffer.

  • Passing in sympy.Basic, sympy.Expr and sympy.Matrix types as instruction parameters are deprecated and will be removed in a future release. You’ll need to convert the input to one of the supported types which are:

    • int
    • float
    • complex
    • str
    • np.ndarray

Bug Fixes

  • The Collect2qBlocks and CommutationAnalysis passes in the transpiler had been unable to process circuits containing Parameterized gates, preventing Parameterized circuits from being transpiled at optimization_level 2 or above. These passes have been corrected to treat Parameterized gates as opaque.
  • The align_measures function had an issue where Measure stimulus pulses weren’t properly aligned with Acquire pulses, resulting in an error. This has been fixed.
  • Uses of numpy.random.seed have been removed so that calls of qiskit functions do not affect results of future calls to numpy.random
  • Fixed race condition occurring in the job monitor when job.queue_position() returns None. None is a valid return from job.queue_position().
  • Backend support for memory=True now checked when that kwarg is passed. QiskitError results if not supported.
  • When transpiling without a coupling map, there were no check in the amount of qubits of the circuit to transpile. Now the transpile process checks that the backend has enough qubits to allocate the circuit.

Other Notes

  • The qiskit.result.marginal_counts() function replaces a similar utility function in qiskit-ignis qiskit.ignis.verification.tomography.marginal_counts(), which will be deprecated in a future qiskit-ignis release.
  • All sympy parameter output type support have been been removed (or deprecated as noted) from qiskit-terra. This includes sympy type parameters in QuantumCircuit objects, qasm ast nodes, or Qobj objects.

Aer 0.3

No Change

Ignis 0.2

No Change

Aqua 0.6

No Change

IBM Q Provider 0.4

Prelude

The 0.4.0 release is the first release that makes use of all the features of the new IBM Q API. In particular, the IBMQJob class has been revamped in order to be able to retrieve more information from IBM Q, and a Job Manager class has been added for allowing a higher-level and more seamless usage of large or complex jobs. If you have not upgraded from the legacy IBM Q Experience or QConsole yet, please ensure to revisit the release notes for IBM Q Provider 0.3 (Qiskit 0.11) for more details on how to make the transition. The legacy accounts will no longer be supported as of this release.

New Features

Job modifications

The IBMQJob class has been revised, and now mimics more closely to the contents of a remote job along with new features:

  • You can now assign a name to a job, by specifying IBMQBackend.run(..., job_name='...') when submitting a job. This name can be retrieved via IBMQJob.name() and can be used for filtering.
  • Jobs can now be shared with other users at different levels (global, per hub, group or project) via an optional job_share_level parameter when submitting the job.
  • IBMQJob instances now have more attributes, reflecting the contents of the remote IBM Q jobs. This implies that new attributes introduced by the IBM Q API will automatically and immediately be available for use (for example, job.new_api_attribute). The new attributes will be promoted to methods when they are considered stable (for example, job.name()).
  • .error_message() returns more information on why a job failed.
  • .queue_position() accepts a refresh parameter for forcing an update.
  • .result() accepts an optional partial parameter, for returning partial results, if any, of jobs that failed. Be aware that Result methods, such as get_counts() will raise an exception if applied on experiments that failed.

Please note that the changes include some low-level modifications of the class. If you were creating the instances manually, note that:

  • the signature of the constructor has changed to account for the new features.
  • the .submit() method can no longer be called directly, and jobs are expected to be submitted either via the synchronous IBMQBackend.run() or via the Job Manager.
Job Manager

A new Job Manager (IBMQJobManager) has been introduced, as a higher-level mechanism for handling jobs composed of multiple circuits or pulse schedules. The Job Manager aims to provide a transparent interface, intelligently splitting the input into efficient units of work and taking full advantage of the different components. It will be expanded on upcoming versions, and become the recommended entry point for job submission.

Its .run() method receives a list of circuits or pulse schedules, and returns a ManagedJobSet instance, which can then be used to track the statuses and results of these jobs. For example:

from qiskit.providers.ibmq.managed import IBMQJobManager
from qiskit.circuit.random import random_circuit
from qiskit import IBMQ
from qiskit.compiler import transpile
 
provider = IBMQ.load_account()
backend = provider.backends.ibmq_ourense
 
circs = []
for _ in range(1000000):
    circs.append(random_circuit(2, 2))
transpile(circs, backend=backend)
 
# Farm out the jobs.
jm = IBMQJobManager()
job_set = jm.run(circs, backend=backend, name='foo')
 
job_set.statuses()    # Gives a list of job statuses
job_set.report()    # Prints detailed job information
results = job_set.results()
counts = results.get_counts(5)   # Returns data for experiment 5
provider.backends modifications

The provider.backends member, which was previously a function that returned a list of backends, has been promoted to a service. This implies that it can be used both in the previous way, as a .backends() method, and also as a .backends attribute with expanded capabilities:

  • it contains the existing backends from that provider as attributes, which can be used for autocompletion. For example:

    my_backend = provider.get_backend('ibmq_qasm_simulator')

    is equivalent to:

    my_backend = provider.backends.ibmq_qasm_simulator

  • the provider.backends.jobs() and provider.backends.retrieve_job() methods can be used for retrieving provider-wide jobs.

Other changes
  • The backend.properties() function now accepts an optional datetime parameter. If specified, the function returns the backend properties closest to, but older than, the specified datetime filter.
  • Some warnings have been toned down to logger.warning messages.
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