# Results

Struct which represents a gradient computation using the adjoint differentiation method on a Circuit.

Constructs an AdjointGradient with respect to the expectation value of an observable o on qubits targets. The gradient will be calculated by computing partial derivatives with respect to parameters. If parameters is not present, is empty, or is ["all"], all parameters in the circuit will be used.

targets may be one of:

AdjointGradient supports using Sum observables. If o is a Sum, targets should be a nested vector of target qubits, such that the n-th term of targets has the same length as the n-th term of o.

Examples

julia> α = FreeParameter(:alpha);

julia> c = Circuit([(H, 0), (H, 1), (Rx, 0, α), (Rx, 1, α)]);

julia> op = 2.0 * Braket.Observables.X() * Braket.Observables.X();

Using a Sum:

julia> α = FreeParameter(:alpha);

julia> c = Circuit([(H, 0), (H, 1), (Rx, 0, α), (Rx, 1, α)]);

julia> op1 = 2.0 * Braket.Observables.X() * Braket.Observables.X();

julia> op2 = -3.0 * Braket.Observables.Y() * Braket.Observables.Y();

julia> c = AdjointGradient(c, op1 + op2, [QubitSet(0, 1), QubitSet(0, 2)], [α]);

Constructs an AdjointGradient computation with respect to the expectation value of an observable o on qubits targets, computing partial derivatives of parameters, and adds it as a result to Circuit c.

o may be any Observable. targets must be a Vector of QubitSets (or a single QubitSet, if o is not a Sum), each of which is the same length as the qubit count of the corresponding term in o. parameters can have elements which are FreeParameters or Strings, or ["all"], in which case the gradient is computed with respect to all parameters in the circuit.

Examples

julia> c = Circuit();

julia> α = FreeParameter("alpha");

julia> c = H(c, collect(0:10));

julia> c = Rx(c, collect(0:10), α);

Braket.ExpectationMethod
Expectation(o, targets) -> Expectation
Expectation(o) -> Expectation

Constructs a Expectation of an observable o on qubits targets.

o may be one of:

• Any Observable
• A String corresponding to an Observable (e.g. "x")
• A Vector{String} in which each element corresponds to an Observable

targets may be one of:

• A QubitSet
• A Vector of Ints and/or Qubits
• An Int or Qubit
• Absent, in which case the observable o will be applied to all qubits provided it is a single qubit observable.
Braket.ExpectationMethod
Expectation(c::Circuit, o, targets) -> Circuit
Expectation(c::Circuit, o) -> Circuit

Constructs a Expectation of an observable o on qubits targets and adds it as a result to Circuit c.

o may be one of:

• Any Observable
• A String corresponding to an Observable (e.g. "x")
• A Vector{String} in which each element corresponds to an Observable

targets may be one of:

• A QubitSet
• A Vector of Ints and/or Qubits
• An Int or Qubit
• Absent, in which case the observable o will be applied to all qubits provided it is a single qubit observable.

Examples

julia> c = Circuit();

julia> c = H(c, collect(0:10));

julia> c = Expectation(c, Braket.Observables.Z(), 0);

julia> c = Expectation(c, Braket.Observables.X());
Braket.VarianceMethod
Variance(o, targets) -> Variance
Variance(o) -> Variance

Constructs a Variance of an observable o on qubits targets.

o may be one of:

• Any Observable
• A String corresponding to an Observable (e.g. "x")
• A Vector{String} in which each element corresponds to an Observable

targets may be one of:

• A QubitSet
• A Vector of Ints and/or Qubits
• An Int or Qubit
• Absent, in which case the observable o will be applied to all qubits provided it is a single qubit observable.
Braket.VarianceMethod
Variance(c::Circuit, o, targets) -> Circuit
Variance(c::Circuit, o) -> Circuit

Constructs a Variance of an observable o on qubits targets and adds it as a result to Circuit c.

o may be one of:

• Any Observable
• A String corresponding to an Observable (e.g. "x")
• A Vector{String} in which each element corresponds to an Observable

targets may be one of:

• A QubitSet
• A Vector of Ints and/or Qubits
• An Int or Qubit
• Absent, in which case the observable o will be applied to all qubits provided it is a single qubit observable.

Examples

julia> c = Circuit();

julia> c = H(c, collect(0:10));

julia> c = Variance(c, Braket.Observables.Z(), 0);

julia> c = Variance(c, Braket.Observables.X());
Braket.SampleMethod
Sample(o, targets) -> Sample
Sample(o) -> Sample

Constructs a Sample of an observable o on qubits targets.

o may be one of:

• Any Observable
• A String corresponding to an Observable (e.g. "x"`)
• A Vector{String} in which each element corresponds to an Observable

targets may be one of:

• A QubitSet
• A Vector of Ints and/or Qubits
• An Int or Qubit
• Absent, in which case the observable o will be applied to all qubits provided it is a single qubit observable.
Braket.SampleMethod
Sample(c::Circuit, o, targets) -> Circuit
Sample(c::Circuit, o) -> Circuit

Constructs a Sample of an observable o on qubits targets and adds it as a result to Circuit c.

o may be one of:

• Any Observable
• A String corresponding to an Observable (e.g. "x")
• A Vector{String} in which each element corresponds to an Observable

targets may be one of:

• A QubitSet
• A Vector of Ints and/or Qubits
• An Int or Qubit
• Absent, in which case the observable o will be applied to all qubits provided it is a single qubit observable.

Examples

julia> c = Circuit();

julia> c = H(c, collect(0:10));

julia> c = Sample(c, Braket.Observables.Z(), 0);

julia> c = Sample(c, Braket.Observables.X());
Braket.AmplitudeMethod
Amplitude(states) -> Amplitude

Constructs an Amplitude measurement of states.

states may be one of:

• A Vector{String}
• A String

All elements of states must be '0' or '1'.

Braket.AmplitudeMethod
Amplitude(c::Circuit, states) -> Circuit

Constructs an Amplitude measurement of states and adds it as a result to Circuit c.

states may be of type:

• Vector{String}
• String

All elements of states must be '0' or '1'.

Examples

julia> c = Circuit();

julia> c = H(c, collect(0:3));

julia> c = Amplitude(c, "0000");
Braket.ProbabilityMethod
Probability(targets) -> Probability
Probability() -> Probability

Constructs a Probability on qubits targets.

targets may be one of:

• A QubitSet
• A Vector of Ints and/or Qubits
• An Int or Qubit
• Absent, in which case the measurement will be applied to all qubits.
Braket.ProbabilityMethod
Probability(c::Circuit, targets) -> Circuit
Probability(c::Circuit) -> Circuit

Constructs a Probability measurement on qubits targets and adds it as a result to Circuit c.

targets may be one of:

• A QubitSet
• A Vector of Ints and/or Qubits
• An Int or Qubit
• Absent, in which case the measurement will be applied to all qubits of c.

Examples

julia> c = Circuit();

julia> c = H(c, collect(0:3));

julia> c = Probability(c, 2);
Braket.DensityMatrixMethod
DensityMatrix(targets) -> DensityMatrix
DensityMatrix() -> DensityMatrix

Constructs a DensityMatrix on qubits targets.

targets may be one of:

• A QubitSet
• A Vector of Ints and/or Qubits
• An Int or Qubit
• Absent, in which case the measurement will be applied to all qubits.
Braket.DensityMatrixMethod
DensityMatrix(c::Circuit, targets) -> Circuit

Constructs a DensityMatrix measurement on qubits targets and adds it as a result to Circuit c.

targets may be one of:

• A QubitSet
• A Vector of Ints and/or Qubits
• An Int or Qubit
• Absent, in which case the measurement will be applied to all qubits of c.

Examples

julia> c = Circuit();

julia> c = H(c, collect(0:3));

julia> c = DensityMatrix(c, 2);
Braket.StateVectorMethod
StateVector(c::Circuit) -> Circuit

Constructs a StateVector measurement on all qubits of c and adds it as a result to Circuit c.

Examples

julia> c = Circuit();

julia> c = H(c, collect(0:3));

julia> c = StateVector(c);