Physlib

QuantumInfo.Finite.CPTPMap.Bundled

51 declarations

abbrev

Underlying linear map of a Hermitian-preserving map Λ\Lambda

#map

Let Λ\Lambda be a Hermitian-preserving matrix map from matrices of dimension dind_{in} to matrices of dimension doutd_{out} over a field k\mathbb{k}. The function Λ.map\Lambda.\text{map} returns the underlying linear map M:Matdin(k)Matdout(k)M: \text{Mat}_{d_{in}}(\mathbb{k}) \to \text{Mat}_{d_{out}}(\mathbb{k}) associated with Λ\Lambda.

theorem

Extensionality of Hermitian-preserving maps

#ext

Let Λ1\Lambda_1 and Λ2\Lambda_2 be Hermitian-preserving matrix maps. If their underlying matrix mapping functions are equal (i.e., Λ1.map=Λ2.map\Lambda_1.\text{map} = \Lambda_2.\text{map}), then the bundled maps Λ1\Lambda_1 and Λ2\Lambda_2 are equal.

theorem

Hermitian-preserving maps are equal if they agree on all Hermitian matrices

#funext_hermitian

Let Λ1\Lambda_1 and Λ2\Lambda_2 be Hermitian-preserving matrix maps from matrices of dimension dind_{in} to matrices of dimension doutd_{out} over C\mathbb{C}. If for every Hermitian matrix MM of dimension dind_{in}, the maps agree such that Λ1(M)=Λ2(M)\Lambda_1(M) = \Lambda_2(M), then the maps themselves are equal (Λ1=Λ2\Lambda_1 = \Lambda_2).

theorem

Hermitian-preserving maps are equal if they agree on all positive semidefinite matrices

#funext_pos

Let CΛ1C\Lambda_1 and CΛ2C\Lambda_2 be hermitian-preserving matrix maps from dIndIn to dOutdOut over C\mathbb{C}. If for every hermitian matrix MM of dimension dIndIn that is positive semidefinite (0M0 \le M), the maps agree such that CΛ1(M)=CΛ2(M)C\Lambda_1(M) = C\Lambda_2(M), then the maps themselves are equal (CΛ1=CΛ2C\Lambda_1 = C\Lambda_2).

theorem

Hermitian-preserving maps are equal if they agree on all positive semidefinite matrices with trace one

#funext_pos_trace

Let CΛ1C\Lambda_1 and CΛ2C\Lambda_2 be hermitian-preserving matrix maps from dIndIn to dOutdOut over the complex numbers C\mathbb{C}. If for every hermitian matrix MM of dimension dIndIn that is both positive semidefinite (0M0 \le M) and has a trace equal to one (M.trace=1M.\text{trace} = 1), the maps agree such that CΛ1(M)=CΛ2(M)C\Lambda_1(M) = C\Lambda_2(M), then the maps themselves are equal (CΛ1=CΛ2C\Lambda_1 = C\Lambda_2).

theorem

Hermitian-preserving maps are equal if they agree on all mixed states ρ\rho

#funext_mstate

Let Λ1\Lambda_1 and Λ2\Lambda_2 be Hermitian-preserving matrix maps from dIn×dInd_{In} \times d_{In} matrices to dOut×dOutd_{Out} \times d_{Out} matrices over the complex numbers C\mathbb{C}. If for every mixed state ρ\rho of dimension dInd_{In}, the maps agree on the underlying matrix representation m(ρ)m(\rho) of the state, such that Λ1(m(ρ))=Λ2(m(ρ))\Lambda_1(m(\rho)) = \Lambda_2(m(\rho)), then the maps are equal (Λ1=Λ2\Lambda_1 = \Lambda_2). (Here, a mixed state ρ\rho is a positive semidefinite Hermitian matrix with trace 1).

instance

Function-like instance for Hermitian-preserving maps `HPMap`

#instFunLike

The type `HPMap dIn dOut ℂ` of Hermitian-preserving maps is endowed with a function-like structure (`FunLike`). This allows an element ΛHPMap(dIn,dOut,C)\Lambda \in \text{HPMap}(d_{In}, d_{Out}, \mathbb{C}) to be treated as a function that maps a Hermitian matrix ρHermitianMatdIn(C)\rho \in \text{HermitianMat}_{d_{In}}(\mathbb{C}) to a Hermitian matrix in HermitianMatdOut(C)\text{HermitianMat}_{d_{Out}}(\mathbb{C}). The value of this function is defined as Λ(ρ)=Λ.map(ρmat)\Lambda(\rho) = \Lambda.\text{map}(\rho_{mat}), where Λ.map\Lambda.\text{map} is the underlying linear map on complex matrices.

theorem

Evaluation of an `HPMap` on a `HermitianMat`ρ\rho equals Λ(ρ)\Lambda(\rho)

#apply_hermitianMat_eq

Let Λ\Lambda be a Hermitian-preserving map (an `HPMap`) from din×dind_{in} \times d_{in} matrices to dout×doutd_{out} \times d_{out} matrices over the complex numbers C\mathbb{C}. Let ρ\rho be a Hermitian matrix of dimension dind_{in} (represented as a subtype consisting of a matrix and a proof of its Hermiticity). The application of Λ\Lambda to ρ\rho, denoted by Λρ\Lambda \rho, is equal to the Hermitian matrix whose underlying matrix is Λ.map(ρ.1)\Lambda.\text{map}(\rho.1) and whose proof of Hermiticity is Λ.HP(ρ.2)\Lambda.\text{HP}(\rho.2).

instance

Hermitian-preserving maps are continuous R\mathbb{R}-linear maps between Hermitian matrix spaces

#instContinuousLinearMapClassComplexRealHermitianMat

Let dInd_{In} be a finite type (dimension index) and dOutd_{Out} be a type. Let HPMap(dIn,dOut,C)\text{HPMap}(d_{In}, d_{Out}, \mathbb{C}) be the type of Hermitian-preserving linear maps between complex matrices of these dimensions. There exists an instance of `ContinuousLinearMapClass` for HPMap(dIn,dOut,C)\text{HPMap}(d_{In}, d_{Out}, \mathbb{C}) over the scalar field R\mathbb{R}, treating the space of Hermitian matrices HermitianMat(d,C)\text{HermitianMat}(d, \mathbb{C}) as a real vector space. This characterizes complex Hermitian-preserving maps as continuous R\mathbb{R}-linear maps when restricted to the domain and codomain of Hermitian matrices.

theorem

Extensionality of positive-preserving maps (PMaps)

#ext

Let Λ1\Lambda_1 and Λ2\Lambda_2 be positive-preserving maps (of type `PMap`) from input dimension dIndIn to output dimension dOutdOut over a field k\mathbb{k}. If the underlying matrix maps associated with Λ1\Lambda_1 and Λ2\Lambda_2 are equal (i.e., Λ1.map=Λ2.map\Lambda_1.\text{map} = \Lambda_2.\text{map}), then the positive-preserving maps themselves are equal (Λ1=Λ2\Lambda_1 = \Lambda_2).

theorem

Injectivity of the conversion from positive-preserving maps to Hermitian-preserving maps

#injective_toHPMap

Let dInd_{In} and dOutd_{Out} be finite types and k\mathbb{k} be a field (typically C\mathbb{C} or R\mathbb{R}). Consider the mapping `toHPMap` which casts a positive-preserving map (an element of `PMap`) to its underlying Hermitian-preserving map (an element of `HPMap`). This mapping is injective; that is, if two positive-preserving maps map to the same Hermitian-preserving map, they are identical.

instance

PMap\text{PMap} is a function type from HermitianMat(dIn,C)\text{HermitianMat}(d_{In}, \mathbb{C}) to HermitianMat(dOut,C)\text{HermitianMat}(d_{Out}, \mathbb{C})

#instFunLike

The type of positive-preserving maps PMap\text{PMap} between complex matrices of dimensions dInd_{In} and dOutd_{Out} behaves like a type of functions. It maps a Hermitian matrix ρHermitianMat(dIn,C)\rho \in \text{HermitianMat}(d_{In}, \mathbb{C}) to another Hermitian matrix Λ(ρ)HermitianMat(dOut,C)\Lambda(\rho) \in \text{HermitianMat}(d_{Out}, \mathbb{C}). This is implemented by composing the coercion of its underlying Hermitian-preserving map with the conversion from a positive-preserving map.

theorem

Evaluation of a Positive-Preserving Map on a Hermitian Matrix

#apply_hermitianMat_eq

Let Λ\Lambda be a positive-preserving map (an element of `PMap`) between the spaces of matrices of dimensions dInd_{In} and dOutd_{Out} over the complex numbers C\mathbb{C}. Let ρ\rho be a Hermitian matrix of dimension dInd_{In}, represented as a subtype pair ρ.1,ρ.2\langle\rho.1, \rho.2\rangle where ρ.1\rho.1 is the underlying matrix and ρ.2\rho.2 is the proof of its hermiticity. The application of the map Λ\Lambda to ρ\rho is equal to the Hermitian matrix whose underlying matrix is Λ.map\Lambda.map applied to ρ.1\rho.1, and whose hermiticity proof is given by the fact that Λ\Lambda is a Hermitian-preserving map (Λ.HP\Lambda.HP).

instance

The type of positive-preserving maps PMap\text{PMap} is a R\mathbb{R}-linear map class between Hermitian matrix spaces

#instLinearMapClass

Let PMap(dIn,dOut,C)\text{PMap}(d_{In}, d_{Out}, \mathbb{C}) be the type of positive-preserving maps between matrices of dimension dInd_{In} and dOutd_{Out} over the complex numbers C\mathbb{C}. These maps satisfy the properties of a linear map class over the real numbers R\mathbb{R}, mapping the space of Hermitian matrices of dimension dInd_{In} to the space of Hermitian matrices of dimension dOutd_{Out}.

instance

PMap\text{PMap} is a Class of Continuous Order Homomorphisms between Hermitian Matrix Spaces

#instContinuousOrderHomClass

The type of positive-preserving maps PMap(dIn,dOut,C)\text{PMap}(d_{In}, d_{Out}, \mathbb{C}) between spaces of complex matrices is an instance of a continuous order-preserving homomorphism class (`ContinuousOrderHomClass`). This means that for any such map Λ\Lambda, the induced function from the space of Hermitian matrices HermitianMat(dIn,C)\text{HermitianMat}(d_{In}, \mathbb{C}) to HermitianMat(dOut,C)\text{HermitianMat}(d_{Out}, \mathbb{C}) is both continuous and monotonic with respect to the Loewner order (the partial order \le defined by positive semidefiniteness).

theorem

PMaps preserve positivity of Hermitian matrices

#pos_Hermitian

Let MM be a positive-preserving map (PMap) from din×dind_{\text{in}} \times d_{\text{in}} complex matrices to dout×doutd_{\text{out}} \times d_{\text{out}} complex matrices. For any Hermitian matrix xx of dimension dind_{\text{in}} such that xx is positive semidefinite (0x0 \le x), the image M(x)M(x) is also positive semidefinite (0M(x)0 \le M(x)).

definition

Completely positive map from Kraus operators {Mk}\{M_k\}

#of_kraus_CPMap

Given a finite collection of matrices {Mk}kκ\{M_k\}_{k \in \kappa} where each MkM_k is a matrix of size dout×dind_{\text{out}} \times d_{\text{in}} over a field K\mathbb{K} (typically C\mathbb{C}), the map defined by the Kraus representation Φ(A)=kκMkAMk\Phi(A) = \sum_{k \in \kappa} M_k A M_k^\dagger is a completely positive map (CPMap) from din×dind_{\text{in}} \times d_{\text{in}} matrices to dout×doutd_{\text{out}} \times d_{\text{out}} matrices. Here, the underlying linear map is constructed using `MatrixMap.of_kraus`, and its complete positivity is guaranteed by the property that any map in Kraus form is completely positive.

theorem

Extensionality of PTP maps via their underlying linear maps

#ext

Let Λ1\Lambda_1 and Λ2\Lambda_2 be positive trace-preserving maps (PTP maps) between matrix spaces over a field K\mathbb{K}. If the underlying linear maps associated with Λ1\Lambda_1 and Λ2\Lambda_2 are equal (i.e., Λ1.map=Λ2.map\Lambda_1.\text{map} = \Lambda_2.\text{map}), then Λ1\Lambda_1 and Λ2\Lambda_2 are equal as PTP maps.

theorem

The map from PTP maps to P maps is injective

#injective_toPMap

Let PTPMap(din,dout,K)\text{PTPMap}(d_{in}, d_{out}, \mathbb{K}) be the space of positive trace-preserving maps between matrix spaces over a field K\mathbb{K}, and let PMap(din,dout,K)\text{PMap}(d_{in}, d_{out}, \mathbb{K}) be the space of positive-preserving maps. The canonical projection (or coercion) f:PTPMapPMapf: \text{PTPMap} \to \text{PMap}, which maps a positive trace-preserving map to its underlying positive-preserving map, is injective.

instance

PTPMap\text{PTPMap} is a function type from HermitianMat(dIn,C)\text{HermitianMat}(d_{In}, \mathbb{C}) to HermitianMat(dOut,C)\text{HermitianMat}(d_{Out}, \mathbb{C})

#instFunLike

The type of positive trace-preserving maps PTPMap\text{PTPMap} between complex matrices of dimensions dInd_{In} and dOutd_{Out} is equipped with an instance that allows it to behave as a type of functions. Specifically, it maps a Hermitian matrix ρHermitianMat(dIn,C)\rho \in \text{HermitianMat}(d_{In}, \mathbb{C}) to another Hermitian matrix Λ(ρ)HermitianMat(dOut,C)\Lambda(\rho) \in \text{HermitianMat}(d_{Out}, \mathbb{C}). This function behavior is defined by composing the coercion of its underlying positive-preserving map (PMap\text{PMap}) with the conversion from a positive trace-preserving map.

theorem

Agreement of Λ(ρ)\Lambda(\rho) and Λ.toPMap(ρ)\Lambda.\text{toPMap}(\rho) for Hermitian Matrices

#apply_hermitianMat_eq_toPMap

Let Λ\Lambda be a positive trace-preserving map (PTP map) from input dimension dInd_{In} to output dimension dOutd_{Out} over the complex numbers C\mathbb{C}. For any Hermitian matrix ρ\rho of dimension dInd_{In}, the application of Λ\Lambda to ρ\rho is equal to the application of its underlying positive-preserving map (`toPMap`) to ρ\rho.

instance

PTPMap\text{PTPMap} is a R\mathbb{R}-linear map class between Hermitian matrix spaces

#instLinearMapClass

Let PTPMap(dIn,dOut,C)\text{PTPMap}(d_{In}, d_{Out}, \mathbb{C}) be the type of positive trace-preserving maps between complex matrices of dimensions dInd_{In} and dOutd_{Out}. Then PTPMap(dIn,dOut,C)\text{PTPMap}(d_{In}, d_{Out}, \mathbb{C}) forms a class of R\mathbb{R}-linear maps from the space of Hermitian matrices of dimension dInd_{In} to the space of Hermitian matrices of dimension dOutd_{Out}.

instance

PTPMap\text{PTPMap} is a Continuous Order Homomorphism Class

#instHContinuousOrderHomClass

The type of positive trace-preserving maps (PTPMap\text{PTPMap}) from the space of dIn×dInd_{In} \times d_{In} Hermitian matrices to dOut×dOutd_{Out} \times d_{Out} Hermitian matrices over the complex numbers C\mathbb{C} forms a class of continuous order-preserving homomorphisms. Specifically, every such map Λ\Lambda is continuous and monotone, meaning that for any Hermitian matrices ρ1,ρ2HermitianMat(dIn,C)\rho_1, \rho_2 \in \text{HermitianMat}(d_{In}, \mathbb{C}), if ρ1ρ2\rho_1 \le \rho_2 (in the Loewner order), then Λ(ρ1)Λ(ρ2)\Lambda(\rho_1) \le \Lambda(\rho_2).

theorem

PTP Maps preserve positivity of Hermitian matrices

#pos_Hermitian

Let MM be a positive trace-preserving (PTP) map from the space of Hermitian matrices of dimension dInd_{In} to dOutd_{Out} over the complex numbers C\mathbb{C}. For any Hermitian matrix xx of dimension dInd_{In} such that xx is positive semidefinite (0x0 \le x), the result of applying the map M(x)M(x) is also positive semidefinite (0M(x)0 \le M(x)).

instance

`PTPMap` is a class of functions from `MState dIn` to `MState dOut`

#instMFunLike

The structure of positive trace-preserving maps (`PTPMap`) from an input dimension dInd_{In} to an output dimension dOutd_{Out} acts as a type of functions between mixed states. Specifically, for any such map Λ\Lambda and any mixed state ρ\rho of dimension dInd_{In}, the application Λ(ρ)\Lambda(\rho) is defined as the mixed state in dimension dOutd_{Out} whose underlying Hermitian matrix is the image of the matrix of ρ\rho under the map. This mapping is well-defined because Λ\Lambda preserves both the positive semidefiniteness and the unit trace of the state, and it is injective relative to the underlying linear map.

theorem

The application of a PTP map to a mixed state preserves mixed state properties

#apply_mstate_eq

Let Λ\Lambda be a positive trace-preserving map (PTP map) from input dimension dInd_{In} to output dimension dOutd_{Out} over the complex numbers C\mathbb{C}. Let ρ\rho be a mixed state of dimension dInd_{In} with associated Hermitian matrix ρ.M\rho.M (which is positive semidefinite and has trace 1). The application of the map Λ\Lambda to the mixed state ρ\rho, denoted Λ(ρ)\Lambda(\rho), is the mixed state in dimension dOutd_{Out} whose underlying matrix is obtained by applying the linear map part of Λ\Lambda to ρ.M\rho.M. This resulting state is well-defined because Λ\Lambda preserves both the positive semidefiniteness and the unit trace of the state.

instance

Positive trace-preserving maps are continuous functions between mixed state spaces

#instMContinuousMapClass

Let dInd_{In} and dOutd_{Out} be finite dimensional Hilbert space indices. The type of positive trace-preserving maps PTPMap(dIn,dOut)\text{PTPMap}(d_{In}, d_{Out}) from input mixed states to output mixed states is an instance of `ContinuousMapClass`. This means that every positive trace-preserving map ΛPTPMap(dIn,dOut)\Lambda \in \text{PTPMap}(d_{In}, d_{Out}) is continuous when viewed as a function between the topological spaces of mixed states MState dIn\text{MState } d_{In} and MState dOut\text{MState } d_{Out}, where both spaces are equipped with the subspace topology inherited from the space of complex matrices.

theorem

The matrix of the PTP-transformed state MρM \rho equals (M as a function)ρ(M \text{ as a function}) \rho

#val_apply_MState

Let MM be a positive trace-preserving (PTP) map from input dimension dInd_{In} to output dimension dOutd_{Out} over the complex numbers C\mathbb{C}. Let ρ\rho be a mixed state (represented by an object of type `MState dIn`). The underlying Hermitian matrix of the mixed state resulting from the application M(ρ)M(\rho) is equal to the result of applying the map MM (coerced as a function) to the Hermitian matrix associated with ρ\rho.

theorem

If the input dimension of a PTP map is non-zero, then the output dimension is non-zero

#nonemptyOut

Let Λ\Lambda be a positive trace-preserving (PTP) map from dIn×dInd_{In} \times d_{In} matrices to dOut×dOutd_{Out} \times d_{Out} matrices. If the input index set dInd_{In} is non-empty, then the output index set dOutd_{Out} must also be non-empty.

theorem

Equality of Matrix Maps Implies Λ1=Λ2\Lambda_1 = \Lambda_2 for CPTP Maps

#ext

Let Λ1\Lambda_1 and Λ2\Lambda_2 be completely positive trace-preserving (CPTP) maps from input dimension dInd_{In} to output dimension dOutd_{Out} over the field k\mathbb{k}. If the underlying linear matrix maps of Λ1\Lambda_1 and Λ2\Lambda_2 are equal, then Λ1=Λ2\Lambda_1 = \Lambda_2.

theorem

The inclusion of CPTP maps into PTP maps is injective

#injective_toPTPMap

Let CPTPMap(dIn,dOut,k)\text{CPTPMap}(d_{In}, d_{Out}, \mathbb{k}) be the set of completely positive trace-preserving linear maps and PTPMap(dIn,dOut,k)\text{PTPMap}(d_{In}, d_{Out}, \mathbb{k}) be the set of positive trace-preserving linear maps between matrix spaces of dimensions dInd_{In} and dOutd_{Out} over the field k\mathbb{k}. The forgetful map Φ:CPTPMapPTPMap\Phi: \text{CPTPMap} \to \text{PTPMap}, which treats a completely positive trace-preserving map as a positive trace-preserving map, is injective.

instance

Function-like instance for CPTP\text{CPTP} maps between matrix states

#instMFunLike

For a completely positive trace-preserving (CPTP) map Λ\Lambda from the space of density matrices (mixed states) MdIn\mathcal{M}_{d_{In}} to MdOut\mathcal{M}_{d_{Out}}, the structure provides an instance of a function-like mapping. Specifically, for any such map Λ\Lambda, there is a corresponding function Λ:MState(dIn)MState(dOut)\Lambda: \text{MState}(d_{In}) \to \text{MState}(d_{Out}) defined by its action on matrix states, ensuring that CPTP maps can be applied directly to states as mathematical functions.

theorem

Agreement of CPTP and PTP Map Application on Quantum States

#apply_mState_eq_toPTPMap

Let Λ\Lambda be a completely positive trace-preserving (CPTP) map from input dimension dInd_{In} to output dimension dOutd_{Out}. For any density matrix (quantum state) ρ\rho of dimension dInd_{In}, the application of Λ\Lambda to ρ\rho is equal to the application of its underlying positive trace-preserving (PTP) map to ρ\rho. That is, Λ(ρ)=toPTPMap(Λ)(ρ)\Lambda(\rho) = \text{toPTPMap}(\Lambda)(\rho).

theorem

The underlying map of a CPTP map is trace-preserving

#IsTracePreserving

Let Λ\Lambda be a completely positive trace-preserving (CPTP) map from din×dind_{in} \times d_{in} matrices to dout×doutd_{out} \times d_{out} matrices over the field k\mathbb{k}. Then its underlying linear map Λ.map\Lambda.\text{map} is trace-preserving.

definition

Construction of a CPTP map from Kraus operators MkM_k satisfying kMkMk=I\sum_k M_k^\dagger M_k = I

#of_kraus_CPTPMap

Given a finite family of matrices {Mk}kκ\{M_k\}_{k \in \kappa} where each MkMatdOut×dIn(k)M_k \in \text{Mat}_{d_{Out} \times d_{In}}(\mathbb{k}) satisfies the completeness relation kκMkMk=I\sum_{k \in \kappa} M_k^\dagger M_k = I, this definition constructs a completely positive trace-preserving (CPTP) map Λ\Lambda from MatdIn(k)\text{Mat}_{d_{In}}(\mathbb{k}) to MatdOut(k)\text{Mat}_{d_{Out}}(\mathbb{k}). The map is defined via the Kraus representation Λ(ρ)=kMkρMk\Lambda(\rho) = \sum_k M_k \rho M_k^\dagger.

theorem

Extensionality of positive unital maps (PUMaps)

#ext

Let Λ1\Lambda_1 and Λ2\Lambda_2 be positive unital maps (of type `PUMap`) from input dimension dInd_{In} to output dimension dOutd_{Out} over a field k\mathbb{k}. If the underlying matrix maps associated with Λ1\Lambda_1 and Λ2\Lambda_2 are equal (i.e., Λ1.map=Λ2.map\Lambda_1.\text{map} = \Lambda_2.\text{map}), then the positive unital maps themselves are equal (Λ1=Λ2\Lambda_1 = \Lambda_2).

theorem

Injectivity of the Forgetful Mapping from Positive Unital Maps to Positive Maps

#injective_toPMap

The function `PUMap.toPMap`, which sends a positive unital map to its underlying positive map, is injective. That is, for any two positive unital maps Λ1\Lambda_1 and Λ2\Lambda_2 between matrix spaces over the field k\mathbb{k}, if their underlying positive maps are equal, then Λ1=Λ2\Lambda_1 = \Lambda_2.

instance

PUMap\text{PUMap} acts as a function from HermitianMat(dIn,C)\text{HermitianMat}(d_{In}, \mathbb{C}) to HermitianMat(dOut,C)\text{HermitianMat}(d_{Out}, \mathbb{C})

#instFunLike

Positive Unital Maps (PUMap\text{PUMap}) from the space of dIn×dInd_{In} \times d_{In} complex Hermitian matrices to dOut×dOutd_{Out} \times d_{Out} complex Hermitian matrices can be treated as functions. Specifically, for any such map Λ\Lambda, its application to a Hermitian matrix ρHermitianMat(dIn,C)\rho \in \text{HermitianMat}(d_{In}, \mathbb{C}) is defined by the action of its underlying positive map.

theorem

Λρ=ΛPρ\Lambda \rho = \Lambda_{P} \rho for Positive Unital Maps

#apply_hermitianMat_eq_toPMap

Let Λ\Lambda be a positive unital map between complex matrix spaces, and let ρ\rho be a Hermitian matrix. The application of the positive unital map Λ\Lambda to ρ\rho is equal to the application of its underlying positive map to ρ\rho.

instance

Positive Unital Maps are R\mathbb{R}-Linear Maps between Hermitian Matrix Spaces

#instLinearMapClass

The type of positive unital maps from dIn×dInd_{In} \times d_{In} complex matrices to dOut×dOutd_{Out} \times d_{Out} complex matrices, denoted as PUMap(dIn,dOut,C)\text{PUMap}(d_{In}, d_{Out}, \mathbb{C}), satisfies the `LinearMapClass` requirements. Specifically, any such map Λ\Lambda acts as an R\mathbb{R}-linear map between the spaces of Hermitian\text{Hermitian} matrices HermitianMat(dIn,C)\text{HermitianMat}(d_{In}, \mathbb{C}) and HermitianMat(dOut,C)\text{HermitianMat}(d_{Out}, \mathbb{C}).

instance

PUMap\text{PUMap} are Continuous Order Homomorphisms between Hermitian Matrix Spaces

#instHContinuousOrderHomClass

Let PUMap(dIn,dOut,C)\text{PUMap}(d_{In}, d_{Out}, \mathbb{C}) be the space of positive unital maps from dIn×dInd_{In} \times d_{In} complex matrices to dOut×dOutd_{Out} \times d_{Out} complex matrices. Any such map ΛPUMap(dIn,dOut,C)\Lambda \in \text{PUMap}(d_{In}, d_{Out}, \mathbb{C}) is a continuous order-preserving homomorphism from the space of Hermitian matrices HermitianMat(dIn,C)\text{HermitianMat}(d_{In}, \mathbb{C}) to HermitianMat(dOut,C)\text{HermitianMat}(d_{Out}, \mathbb{C}). This implies that Λ\Lambda is continuous with respect to the matrix topologies and satisfies AB    Λ(A)Λ(B)A \le B \implies \Lambda(A) \le \Lambda(B) for any Hermitian matrices A,BA, B.

instance

Positive Unital Maps Preserve the Identity Matrix

#instOneHomClass

Let PUMap(dIn,dOut,C)\text{PUMap}(d_{In}, d_{Out}, \mathbb{C}) be the space of positive unital maps from dIn×dInd_{In} \times d_{In} complex matrices to dOut×dOutd_{Out} \times d_{Out} complex matrices. Any such map Λ\Lambda is a "one-preserving homomorphism" between the spaces of Hermitian matrices HermitianMat(dIn,C)\text{HermitianMat}(d_{In}, \mathbb{C}) and HermitianMat(dOut,C)\text{HermitianMat}(d_{Out}, \mathbb{C}). Specifically, Λ\Lambda maps the identity matrix IdInI_{d_{In}} to the identity matrix IdOutI_{d_{Out}} (i.e., Λ(I)=I\Lambda(I) = I).

theorem

Positive Unital Maps Preserve Positivity of Hermitian Matrices

#pos_Hermitian

Let MM be a positive unital map from the space of dIn×dInd_{In} \times d_{In} complex matrices to dOut×dOutd_{Out} \times d_{Out} complex matrices. For any Hermitian matrix xx of size dInd_{In} such that xx is positive semidefinite (0x0 \le x), its image under the map MxM x is also positive semidefinite (0Mx0 \le M x).

theorem

Extensionality of completely positive unital maps (CPUMaps)

#ext

Let Λ1\Lambda_1 and Λ2\Lambda_2 be completely positive unital maps (of type `CPUMap`) from input dimension dind_{in} to output dimension doutd_{out} over a field k\mathbb{k}. If the underlying linear maps associated with Λ1\Lambda_1 and Λ2\Lambda_2 are equal (i.e., Λ1.map=Λ2.map\Lambda_1.\text{map} = \Lambda_2.\text{map}), then the completely positive unital maps themselves are equal (Λ1=Λ2\Lambda_1 = \Lambda_2).

theorem

The map CPUMapCPMapPMapCPUMap \to CPMap \to PMap is injective

#injective_toPMap

The composition of the forgetful map from completely positive unital maps (CPUMapCPUMap) to completely positive maps (CPMapCPMap) and the forgetful map from completely positive maps to positive-preserving maps (PMapPMap) is injective. In other words, a completely positive unital map Λ\Lambda is uniquely determined by its underlying positive-preserving map.

instance

CPUMap\text{CPUMap} is a function type from HermitianMat(dIn,C)\text{HermitianMat}(d_{In}, \mathbb{C}) to HermitianMat(dOut,C)\text{HermitianMat}(d_{Out}, \mathbb{C})

#instFunLike

The type of completely positive unital maps, denoted as CPUMap(dIn,dOut,C)\text{CPUMap}(d_{In}, d_{Out}, \mathbb{C}), acts as a space of functions. Specifically, each element Λ\Lambda in this type maps a Hermitian matrix ρHermitianMat(dIn,C)\rho \in \text{HermitianMat}(d_{In}, \mathbb{C}) to a Hermitian matrix Λ(ρ)HermitianMat(dOut,C)\Lambda(\rho) \in \text{HermitianMat}(d_{Out}, \mathbb{C}). This functional behavior is realized through the coercion to its underlying positive-preserving map (PMap\text{PMap}).

theorem

Agreement of CPUMap and PMap actions on Hermitian matrices

#apply_hermitianMat_eq_toPMap

Let Λ\Lambda be a completely positive unital map (CPUMap) from input dimension dInd_{In} to output dimension dOutd_{Out} over the complex numbers C\mathbb{C}. For any Hermitian matrix ρ\rho of dimension dInd_{In} over C\mathbb{C}, the action of Λ\Lambda on ρ\rho is equal to the action of its underlying positive-preserving map (PMap) on ρ\rho.

instance

The type of completely positive unital maps CPUMap\text{CPUMap} is a R\mathbb{R}-linear map class between Hermitian matrix spaces

#instLinearMapClass

Let CPUMap(dIn,dOut,C)\text{CPUMap}(d_{In}, d_{Out}, \mathbb{C}) denote the type of completely positive unital maps between complex matrix spaces of dimensions dInd_{In} and dOutd_{Out}. This type forms a linear map class over the real numbers R\mathbb{R}, acting between the space of dIn×dInd_{In} \times d_{In} complex Hermitian matrices and the space of dOut×dOutd_{Out} \times d_{Out} complex Hermitian matrices.

instance

Completely positive unital maps are continuous order-preserving homomorphisms

#instHContinuousOrderHomClass

The type of completely positive unital maps from din×dind_{in} \times d_{in} complex Hermitian matrices to dout×doutd_{out} \times d_{out} complex Hermitian matrices, denoted as `CPUMap dIn dOut ℂ`, satisfies the `ContinuousOrderHomClass` predicates. This means that every such map is a continuous function between the spaces of Hermitian matrices that preserves the partial ordering \le defined on these matrices.

instance

Completely positive unital maps preserve the identity matrix

#instOneHomClass

The type of completely positive unital maps, denoted as `CPUMap dIn dOut ℂ`, which maps complex Hermitian matrices of dimension din×dind_{in} \times d_{in} to those of dimension dout×doutd_{out} \times d_{out}, satisfies the `OneHomClass` predicate. This means that any map MM in this class preserves the identity element, specifically M(Idin)=IdoutM(\mathbb{I}_{d_{in}}) = \mathbb{I}_{d_{out}}, where I\mathbb{I} denotes the identity matrix (the "one" element in the space of Hermitian matrices).

theorem

Completely positive unital maps preserve the positivity of Hermitian matrices

#pos_Hermitian

Let MM be a completely positive unital map from the space of din×dind_{in} \times d_{in} complex Hermitian matrices to the space of dout×doutd_{out} \times d_{out} complex Hermitian matrices. For any Hermitian matrix xHermitianMat(din,C)x \in \text{HermitianMat}(d_{in}, \mathbb{C}), if xx is positive semi-definite (i.e., 0x0 \le x), then its image M(x)M(x) is also positive semi-definite (i.e., 0M(x)0 \le M(x)).