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use crate::chp_decompositions::ChpOperation;
use crate::common_matrices;
use crate::instrument::Instrument;
use crate::linalg::HasDagger;
use crate::processes::Process;
use crate::processes::{
ProcessData,
ProcessData::{KrausDecomposition, Unitary},
};
use crate::states::State;
use crate::states::StateData::Mixed;
use crate::StateData;
use crate::Tableau;
use crate::C64;
use num_traits::{One, Zero};
use serde::{Deserialize, Serialize};
/// A description of the noise that applies to the state of a quantum system
/// as the result of applying operations.
#[derive(Serialize, Deserialize, Debug)]
pub struct NoiseModel {
/// The initial state that freshly allocated qubits start off in.
pub initial_state: State,
/// The process that applies to the state of a simulator
/// when the `I` operation is called.
pub i: Process,
/// The process that applies to the state of a simulator
/// when the `X` operation is called.
pub x: Process,
/// The process that applies to the state of a simulator
/// when the `Y` operation is called.
pub y: Process,
/// The process that applies to the state of a simulator
/// when the `Z` operation is called.
pub z: Process,
/// The process that applies to the state of a simulator
/// when the `H` operation is called.
pub h: Process,
/// The process that applies to the state of a simulator
/// when the `S` operation is called.
pub s: Process,
/// The process that applies to the state of a simulator
/// when the `Adjoint S` operation is called.
pub s_adj: Process,
/// The process that applies to the state of a simulator
/// when the `T` operation is called.
pub t: Process,
/// The process that applies to the state of a simulator
/// when the `Adjoint T` operation is called.
pub t_adj: Process,
/// The process that applies to the state of a simulator
/// when the `CNOT` operation is called.
pub cnot: Process,
/// The instrument that is used to the measure the state of a simulator
/// in the $Z$-basis.
pub z_meas: Instrument,
}
impl NoiseModel {
/// Returns a serialization of this noise model as a JSON object.
pub fn as_json(&self) -> String {
serde_json::to_string(&self).unwrap()
}
/// Given the name of a built-in noise model, returns either that noise
/// model if it exists, or an [`Err`] variant if no such model exists.
///
/// Currently accepted noise model names:
///
/// - `"ideal"`: A full-state noise model in which all operations are
/// ideal (that is, without errors).
/// - `"ideal_stabilizer"`: A noise model in which all operations except
/// [`NoiseModel::t`] and [`NoiseModel::t_adj`] are ideal, and
/// represented in a form compatible with stabilizer simulation.
///
/// # Example
/// ```
/// # use qdk_sim::NoiseModel;
/// let noise_model = NoiseModel::get_by_name("ideal");
/// ```
pub fn get_by_name(name: &str) -> Result<NoiseModel, String> {
match name {
"ideal" => Ok(NoiseModel::ideal()),
"ideal_stabilizer" => Ok(NoiseModel::ideal_stabilizer()),
_ => Err(format!("Unrecognized noise model name {}.", name)),
}
}
/// Returns a copy of the ideal noise model; that is, a noise model
/// describing the case in which no noise acts on the quantum system.
pub fn ideal() -> NoiseModel {
let i = Process {
n_qubits: 1,
data: Unitary(common_matrices::i()),
};
let z = Process {
n_qubits: 1,
data: Unitary(common_matrices::z()),
};
let z_meas = Instrument::Effects(vec![
Process {
n_qubits: 1,
data: KrausDecomposition(array![[
[C64::one(), C64::zero()],
[C64::zero(), C64::zero()]
]]),
},
Process {
n_qubits: 1,
data: KrausDecomposition(array![[
[C64::zero(), C64::zero()],
[C64::zero(), C64::one()]
]]),
},
]);
NoiseModel {
initial_state: State {
n_qubits: 1,
data: Mixed((common_matrices::i() + common_matrices::z()) / 2.0),
},
i,
x: Process {
n_qubits: 1,
data: Unitary(common_matrices::x()),
},
y: Process {
n_qubits: 1,
data: Unitary(common_matrices::y()),
},
z,
h: Process {
n_qubits: 1,
data: Unitary(common_matrices::h()),
},
t: Process {
n_qubits: 1,
data: Unitary(common_matrices::t()),
},
t_adj: Process {
n_qubits: 1,
data: Unitary(common_matrices::t().dag()),
},
s: Process {
n_qubits: 1,
data: Unitary(common_matrices::s()),
},
s_adj: Process {
n_qubits: 1,
data: Unitary(common_matrices::s().dag()),
},
cnot: Process {
n_qubits: 2,
data: Unitary(common_matrices::cnot()),
},
z_meas,
}
}
/// Returns a copy of the ideal noise model suitable for use with
/// stabilizer simulation; that is, a noise model
/// describing the case in which no noise acts on the quantum system, and
/// in which all channels can be represented by CHP decompositions.
pub fn ideal_stabilizer() -> NoiseModel {
NoiseModel {
initial_state: State {
n_qubits: 1,
data: StateData::Stabilizer(Tableau::new(1)),
},
i: Process {
n_qubits: 1,
data: ProcessData::Sequence(vec![]),
},
x: Process {
n_qubits: 1,
data: ProcessData::ChpDecomposition(vec![
ChpOperation::Hadamard(0),
ChpOperation::Phase(0),
ChpOperation::Phase(0),
ChpOperation::Hadamard(0),
]),
},
y: Process {
n_qubits: 1,
data: ProcessData::ChpDecomposition(vec![
ChpOperation::AdjointPhase(0),
ChpOperation::Hadamard(0),
ChpOperation::Phase(0),
ChpOperation::Phase(0),
ChpOperation::Hadamard(0),
ChpOperation::Phase(0),
]),
},
z: Process {
n_qubits: 1,
data: ProcessData::ChpDecomposition(vec![
ChpOperation::Phase(0),
ChpOperation::Phase(0),
]),
},
h: Process {
n_qubits: 1,
data: ProcessData::ChpDecomposition(vec![ChpOperation::Hadamard(0)]),
},
s: Process {
n_qubits: 1,
data: ProcessData::ChpDecomposition(vec![ChpOperation::Phase(0)]),
},
s_adj: Process {
n_qubits: 1,
data: ProcessData::ChpDecomposition(vec![ChpOperation::AdjointPhase(0)]),
},
t: Process {
n_qubits: 1,
data: ProcessData::Unsupported,
},
t_adj: Process {
n_qubits: 1,
data: ProcessData::Unsupported,
},
cnot: Process {
n_qubits: 2,
data: ProcessData::ChpDecomposition(vec![ChpOperation::Cnot(0, 1)]),
},
z_meas: Instrument::ZMeasurement {
pr_readout_error: 0.0,
},
}
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn can_serialize_noise_model() {
let noise_model = NoiseModel::ideal();
let _json = serde_json::to_string(&noise_model);
}
}