Struct NoiseProperties

Struct Documentation

struct NoiseProperties

Use NoiseProperties to accept user input parameters for custom noise models. There are 3 types of inputs used for constructing a custom noise model:

  • Qubit topology

  • Time duration of quantum gate operations

  • Parameters for quantum noise channels and classical errors

Public Members

std::unordered_map<size_t, double> t1_us

T1 is the qubit relaxation time. For a qubit register, with individual qubits zero-indexed by i; t1_us is a map from qubit[i] -> T1[i]. Unit: microseconds 

// C++ code example: 4 qubits all with T1 = 1.5us
qb::NoiseProperties t_qbnp;
t_qbnp.t1_us{{0, 1.5}, {1, 1.5}, {2, 1.5}, {3, 1.5}};

std::unordered_map<size_t, double> t2_us

T2 is the qubit dephasing time. For a qubit register, with individual qubits zero-indexed by i, t2_us is a map from qubit[i] -> T2[i]. Unit: microseconds 

// C++ code example: 4 qubits all with T2 = 0.15us
qb::NoiseProperties t_qbnp;
t_qbnp.t2_us{{0, 0.15}, {1, 0.15}, {2, 0.15}, {3, 0.15}};

std::unordered_map<size_t, ReadoutError> readout_errors

readout_errors is the classical readout error (off-diagonal elements of the confusion matrix). For a qubit register, with individual qubits zero-indexed by i, readout_errors is a map from qubit[i] -> qb::ReadoutError[i]. Unit: none (quantities are probabilities). 

// C++ code example: 2 qubits with p(0|1) = p(1|0) = 0.05, 2 qubits with p(0|1) = 0.1 and p(1|0) = 0.08
qb::NoiseProperties t_qbnp;
qb::ReadoutError t_qbnpro_balanced, t_qbnpro_asym;
t_qbnpro_balanced.p_01 = 0.05;
t_qbnpro_balanced.p_10 = 0.05;
t_qbnpro_asym.p_01 = 0.10;
t_qbnpro_asym.p_10 = 0.08;
t_qbnp.readout_errors{{0, t_qbnpro_balanced}, {1, t_qbnpro_balanced}, {2, t_qbnpro_asym}, {3, t_qbnpro_asym}};

std::unordered_map<std::string, std::map<std::vector<size_t>, double>> gate_time_us

gate_time_us is the duration for a quantum gate operation when applied at a target set of qubits. Unit: microseconds 

// C++ code example: "u3" single-qubit gate, uniform duration 5.2us, 4 qubits
qb::NoiseProperties t_qbnp;
t_qbnp.gate_time_us{{"u3",{{0},5.2}}, {"u3",{{1},5.2}}, {"u3",{{2},5.2}}, {"u3",{{3},5.2}}};

std::unordered_map<std::string, std::map<std::vector<size_t>, double>> gate_pauli_errors

gate_pauli_errors is the parameter for gate error derived from randomized benchmarking of a quantum gate operation that is applied at a target set of qubits. Unit: none 

// C++ code example: "u3" single-qubit gate, gate error parameter = 0.03, uniform for 4 qubits
qb::NoiseProperties t_qbnp;
t_qbnp.gate_pauli_errors{{"u3",{{0},0.03}}, {"u3",{{1},0.03}}, {"u3",{{2},0.03}}, {"u3",{{3},0.03}}};

std::vector<std::pair<int, int>> qubit_topology

qubit_topology is a graph comprised of directed edges {control qubit, target qubit} with control qubit as the source of the edge -> target qubit as the destination of the edge. 

// C++ code example: "cx" symmetrical two-qubit gate with 4 qubits in the topology below:
//    q0 <--cx--> q1
//     ^           ^
//     |           |
//     cx          cx
//     |           |
//     v           v
//    q3 <--cx--> q2
qb::NoiseProperties t_qbnp;
t_qbnp.qubit_topology{{0,1},{1,2},{2,3},{3,0}};