September Release Notes (pytket)¶
The September release brings typing improvements, custom control states in QControlBox
, equality checking for pytket boxes and more.
pytket 1.19.0¶
New Features (Changelog)¶
Fixes (1.19.0)¶
It is now possible to create an empty
BackendResult
object.Performance fix for symbolic angle squashing.
Update - Fixes (1.19.1)¶
Fix for a regression in
RebaseCustom
. TheRebaseCustom
pass would fail to convert circuits containing TK2 gates due to a change released in a previous version. This is now fixed in 1.19.1.Fix to
Circuit.symbol_substitution
for circuits containing box types that don’t support symbol substitution. Boxes which don’t support symbol substitution include the unitary synthesis boxes and assertion boxes.
Typing improvements for compiled pytket modules¶
In previous versions of pytket, type information was not available for any of the compiled modules, which represent a large part of the library.
For this reason, when using type checkers such as mypy or pyright, it was necessary to use # type: ignore
statements like the following.
from pytket.circuit import CircBox # type: ignore
my_circbox = CircBox(...)
This also meant that certain type hints and auto complete feature were not available to developers when using compiled modules such as pytket.circuit
and pytket.passes
.
pytket now includes type information for all compiled modules via automatically generated type stub files. # type: ignore
statements are no longer needed. This means that developers can use type checkers more freely and take advantage of type hints and autocomplete when working with pytket.
Note that using # type: ignore
does not suppress type information if it is available. This means that type checking runs that were previously passing may now fail if the usage of objects from compiled modules is deemed improper by the type checker.
Warning
In order to use some of the pytket extension modules with pytket 1.19.0 or newer, you will need to use a version of the extension package that was released in September 2023 or later. This is due to the typing changes in the pytket 1.19.0 release.
Custom control states in QControlBox
¶
In pytket QControlBox
provides an interface for users to define controlled unitary operations.
Given a pytket Op
we can define a QControlBox
as follows
from pytket.circuit import OpType, Op, QControlBox
s_gate_op = Op.create(OpType.S)
cccs = QControlBox(s_gate_op, 3) # define a CCCS gate
Here we have defined
However prior to the 1.19 release a QControlBox
could only be defined using the “all
This has now changed and QControlBox
now accepts a control_state
argument. If no control_state
argument is provided then the default “all
from pytket.circuit import OpType, Op, QControlBox
s_gate_op = Op.create(OpType.S)
custom_cccs = QControlBox(s_gate_op, 3, control_state=[0, 1, 0])
# Equivalent to the above (using an integer control_state)
# custom_cccs = QControlBox(op, 3, control_state=2)
Now the
These sorts of gates appear frequently in quantum algorithms. Here is a simple example of an LCU (Linear combination of unitaries) circuit.
This circuit can be used to calculate the expectation value of the sum of
Suppose we create a CircBox
for the QControlBox
for the 0-controlled
from pytket.circuit import CircBox, QControlBox
ub_box = CircBox(...)
zero_controlled_ub = QControlBox(ub_box, 1, control_state=[0])
Every pytket Op
now has an is_clifford
method¶
Clifford circuits are an important class of quantum circuits known to exhibit efficient classical simulation.
A Clifford gate is an element of the Clifford group which can be generated by the
For instance a Pauli
Given a pytket Op
we could check whether it was a Clifford type operation with the Op.is_clifford_type
method.
from pytket.circuit import Op, OpType
s_gate_op = Op.create(OpType.S)
s_gate_op.is_clifford_type()
This returns True
, the
However Op.is_clifford_type
is limited as it only checks whether the underlying OpType
is Clifford. This check would not be able to handle the case of parameterised gates that have Clifford angles.
rz_clifford_op = Op.create(OpType.Rz, [1])
rz_clifford_op.is_clifford_type()
Here we have defined the Rz op with the is_clifford_type
method will return False
here as the Rz gate is not in general a Clifford gate.
However in pytket 1.19 we can now use the more general Op.is_clifford()
method.
rz_clifford_op.is_clifford()
This method will now correctly identify the Rz gate as a Clifford by checking whether the parameter is a Clifford angle.
QubitPauliTensor
class¶
The QubitPauliTensor
class is now exposed to pytket. A QubitPauliTensor
is defined using a QubitPauliString
paired with a complex coefficient.
This allows phase to be tracked when using the UnitaryTableau
.
Equality checking for all box types¶
A pytket box represents a higher level subroutine that can be added to a quantum circuit. For more on the different types of box available in pytket, read the user manual section.
After the pytket 1.19 release, every box type now allows for equivalence checking.
from pytket.circuit import Circuit, CircBox
ghz_circ = Circuit(3, name="GHZ").H(0).CX(0, 1).CX(0, 2)
# Construct two equivalent CircBox objects
box1 = CircBox(ghz_circ)
box2 = CircBox(ghz_circ)
box1 == box2
This equality check will now return True
in pytket 1.19. In older versions of pytket, the equality check would return False
.
Being able to test for equivalence is useful for testing purposes. We can validate the CircBox
without decomposing it or having to defer to the underlying circuit with the CircBox.get_circuit()
method.
New ConjugationBox
construction¶
Another enhancement related to controlled gates is the new ConjugationBox
feature. This allows us to find efficient decompositions for controlled gates when our base gate
Where
This compute (
Enhancements to this feature will be added in a subsequent release to handle ConjugationBox
objects inside QControlBox
, enabling more efficient compilation.