pygsti.algorithms.compilers.compile_cnot_circuit

pygsti.algorithms.compilers.compile_cnot_circuit#

compile_cnot_circuit(s, pspec, compilation, qubit_labels=None, algorithm='COiCAGE', compile_to_native=False, check=True, aargs=None, rand_state=None)#

A CNOT circuit compiler.

Takes an arbitrary CNOT circuit, input as a symplectic matrix s that corresponds to the matrix portion of the symplectic representation of this Clifford circuit, and decomposes it into a sequences of gates from the processor spec pspec.

Parameters:

  • s (array over [0,1]) – An (2n X 2n) symplectic matrix of 0s and 1s integers that represents a Clifford circuit: so it must be block-diagonal. Specifically, it has the form s = ((A,0),(0,B)) where B is the inverse transpose of A (over [0,1] mod 2).

  • pspec (QubitProcessorSpec) –

    An nbar-qubit QubitProcessorSpec object that encodes the device that s is being compiled for, where nbar >= n. If this is specified, the output circuit is over the gates available in this device. If this is None, the output circuit is over the “canonical” processor of CNOT gates between all qubits, consisting of “H”, “HP”, “PH”, “HPH”, “I”, “X”, “Y” and “Z”, which is the set used internally for the compilation.

    If nbar > n it is necessary to provide qubit_labels, that specifies which of the qubits in pspec the Clifford acts on. (All other qubits will not be part of the returned circuit, regardless of whether that means an over-head is required to avoid using gates that act on those qubits. If these additional qubits should be used, then the input s needs to be “padded” to be the identity on those qubits).

    The indexing s is assumed to be the same as that in the list pspec.qubit_labels, unless qubit_labels is specified. Then, the ordering is taken w.r.t the ordering of the list qubit_labels.

  • compilation (CompilationRules) – Rules for compiling the “native” gates of pspec into clifford gates, used if compile_to_native==True.

  • qubit_labels (list, optional) – Required if the Clifford to compile is over less qubits than pspec. In this case this is a list of the qubits to compile the Clifford for; it should be a subset of the elements of pspec.qubit_labels. The ordering of the qubits in (s,`p`) is taken w.r.t the ordering of this list.

  • algorithm (str, optional) –

    The algorithm to use. The optionas are:

    • ’BGE’A basic Gaussian elimination algorithm, that uses CNOT to perform row-reduction on the upper

      LHS (or lower RHS) of s. This algorithm does not take device connectivity into account.

    • ’OCAGE’User-ordered connectivity-adjusted Gaussian elimination. The qubits are eliminated in the

      specified order; the first element of arrgs must be a list specify this order. The algorithm is also “connectivity-adjusted” in the sense that it uses the connectivity graph (in pspec.qubit_graph) to try and avoid using CNOTs between unconnected pairs whenever possible, and to decide the order of various operations.

    • ’OiCAGE’The same as ‘OCAGE’ except that it has some improvements, and it requires connectivity

      graph of the remaining qubits, after each qubit has been ‘eliminated’, to be connected. In the current format this algorithm is only slightly better-performing than ‘OCAGE’, and only on average. (This algorithm will possibly be improved in the future, whereas ‘OCAGE’ will remain as-is for reproducibility of previously obtained results.)

    • ’ROCAGE’: Same as ‘OCAGE’ except that the elimination order is chosen at random, rather than user-

      specified.

    • ’COCAGE’, ‘COiCAGE’The same as ‘OCAGE’ and ‘OiCAGE’, respectively, except that the elimination order

      is fixed to eliminate qubits with the worse connectivity before those with better connectivity.

  • compile_to_native (bool, optional) – Whether the circuit should be given in terms of the native gates of the processor defined in pspec.

  • check (bool, optional) – Whether to check the output is correct.

  • aargs (list, optional) – A list of arguments handed to the CNOT compiler algorithm. For some choices of algorithm (e.g., ‘OCAGE’) this list must not be empty. For algorithms where there are X non-optional arguments after s and pspec these are specified as the first X arguments of aargs. The remaining elements in aargs, if any, are handed to the algorithm as the arguments after the optional qubit_labels and check arguments (the first of which is set by the input qubit_labels in this function).

  • rand_state (RandomState, optional) – A np.random.RandomState object for seeding RNG

Returns:

A circuit that implements the same unitary as the CNOT circuit represented by s.

Return type:

Circuit