Documentation

Operator(N::Int)

Initialize an empty operator on N qubits

Operator(o::OperatorTS1D)

Convert an OperatorTS1D to an Operator

OperatorTS1D(o::Operator; full=true)

Initialize a 1D translation invariant operator from an Operator $O=\sum_i o_i O_i$ where $O_i=T_i(O_0)$ and $T_i$ is the i-sites translation operator.
Set full=true if passing $O$, an Operator that is supported on the whole chain (i.e converting from a translation symmetric Operator)
Set full=false if passing $O_0$,a local term o such that the full operator is $O=\sum_i o_i T_i(O_0)$

Base.length(o::Operator)
Base.length(o::OperatorTS1D)

Number of pauli strings in an operator

Example

julia> A = Operator(4)
julia> A += "X111"
julia> A += "XYZ1"
julia> A += 2, "Y", 4
julia> length(A)
3

eye(N::Int)

Identity operator on N qubits

Base.:+(o::Operator, args::Tuple{Number, Vararg{Any}})
Base.:+(o::Operator, args::Tuple{Vararg{Any}})
Base.:+(o::Operator, term::Tuple{Number, String})
Base.:+(o::Operator, term::String)

Main functions to contruct spin operators. Identical signatures are available for -.

Examples

k-local terms can be added by adding a tuple to the operator. The first element of the tuple is an optional coeficient. The other element are couples (symbol,site) where symbol can be "X", "Y", "Z", "Sx", "Sy", "Sz", "S+", "S-" and site is an integer specifying the site on wich the symbol is acting.

A = Operator(4)
A += 2, "X",1,"X",2
A += 3, "Y",1,"X",2
A += "X",3,"X",4
A += 4,"Z",3
A += 5.2,"X",1,"Y",2,"Z",3

julia> A
(4.0 + 0.0im) 11Z1
(3.0 - 0.0im) YX11
(1.0 + 0.0im) 11XX
(2.0 + 0.0im) XX11
(5.2 - 0.0im) XYZ1

Full strings can also be added:

A = Operator(4)
A += 2, "1XXY"
A += 2im, "11Z1"

julia> A
(0.0 + 2.0im) 11Z1
(2.0 - 0.0im) 1XXY

+(x, y...)

Addition operator. x+y+z+... calls this function with all arguments, i.e. +(x, y, z, ...).

Examples

julia> 1 + 20 + 4
25

julia> +(1, 20, 4)
25

+(x, y...)

Addition operator. x+y+z+... calls this function with all arguments, i.e. +(x, y, z, ...).

Examples

julia> 1 + 20 + 4
25

julia> +(1, 20, 4)
25

Base.:+(o::Operator, args::Tuple{Number, Vararg{Any}})
Base.:+(o::Operator, args::Tuple{Vararg{Any}})
Base.:+(o::Operator, term::Tuple{Number, String})
Base.:+(o::Operator, term::String)

Main functions to contruct spin operators. Identical signatures are available for -.

Examples

k-local terms can be added by adding a tuple to the operator. The first element of the tuple is an optional coeficient. The other element are couples (symbol,site) where symbol can be "X", "Y", "Z", "Sx", "Sy", "Sz", "S+", "S-" and site is an integer specifying the site on wich the symbol is acting.

A = Operator(4)
A += 2, "X",1,"X",2
A += 3, "Y",1,"X",2
A += "X",3,"X",4
A += 4,"Z",3
A += 5.2,"X",1,"Y",2,"Z",3

julia> A
(4.0 + 0.0im) 11Z1
(3.0 - 0.0im) YX11
(1.0 + 0.0im) 11XX
(2.0 + 0.0im) XX11
(5.2 - 0.0im) XYZ1

Full strings can also be added:

A = Operator(4)
A += 2, "1XXY"
A += 2im, "11Z1"

julia> A
(0.0 + 2.0im) 11Z1
(2.0 - 0.0im) 1XXY

+(x, y...)

Addition operator. x+y+z+... calls this function with all arguments, i.e. +(x, y, z, ...).

Examples

julia> 1 + 20 + 4
25

julia> +(1, 20, 4)
25

add(o1::Operator, o2::Operator)
Base.:+(o1::Operator, o2::Operator)
Base.:+(o::Operator, a::Number)
Base.:+(a::Number, o::Operator)

Add two operators together or add a number to an operator

Example

A = Operator(4)
A += "XYZ1"
A += 1, "Y", 4
B = Operator(4)
B += 2, "Y", 2, "Y", 4
B += 1, "Z", 3

julia> A
(1.0 - 0.0im) 111Y
(1.0 - 0.0im) XYZ1

julia> B
(1.0 + 0.0im) 11Z1
(2.0 - 0.0im) 1Y1Y

julia> A+B
(1.0 + 0.0im) 11Z1
(2.0 - 0.0im) 1Y1Y
(1.0 - 0.0im) 111Y
(1.0 - 0.0im) XYZ1

julia> A+5
(1.0 - 0.0im) 111Y
(1.0 - 0.0im) XYZ1
(5.0 + 0.0im) 1111

+(x, y...)

Addition operator. x+y+z+... calls this function with all arguments, i.e. +(x, y, z, ...).

Examples

julia> 1 + 20 + 4
25

julia> +(1, 20, 4)
25

+(x, y...)

Addition operator. x+y+z+... calls this function with all arguments, i.e. +(x, y, z, ...).

Examples

julia> 1 + 20 + 4
25

julia> +(1, 20, 4)
25

+(x, y...)

Addition operator. x+y+z+... calls this function with all arguments, i.e. +(x, y, z, ...).

Examples

julia> 1 + 20 + 4
25

julia> +(1, 20, 4)
25

Base.:*(o1::Operator, o2::Operator)
Base.:*(o::Operator, a::Number)
Base.:*(a::Number, o::Operator)

Multiply two operators together or an operator with a number

Example

A = Operator(4)
A += "XYZ1"
A += 1, "Y", 4
B = Operator(4)
B += 2, "Y", 2, "Y", 4
B += 1, "Z", 3

julia> A
(1.0 - 0.0im) 111Y
(1.0 - 0.0im) XYZ1


julia> B
(1.0 + 0.0im) 11Z1
(2.0 - 0.0im) 1Y1Y

julia> A*B
(2.0 - 0.0im) X1ZY
(1.0 - 0.0im) 11ZY
(2.0 - 0.0im) 1Y11
(1.0 - 0.0im) XY11

julia> A*5
(5.0 - 0.0im) 111Y
(5.0 - 0.0im) XYZ1

*(x, y...)

Multiplication operator. x*y*z*... calls this function with all arguments, i.e. *(x, y, z, ...).

Examples

julia> 2 * 7 * 8
112

julia> *(2, 7, 8)
112

*(x, y...)

Multiplication operator. x*y*z*... calls this function with all arguments, i.e. *(x, y, z, ...).

Examples

julia> 2 * 7 * 8
112

julia> *(2, 7, 8)
112

Base.:-(o::Operator)
Base.:-(o1::Operator, o2::Operator)
Base.:-(o::Operator, a::Real)
Base.:-(a::Real, o::Operator)

Subtraction between operators and numbers

-(x, y)

Subtraction operator.

Examples

julia> 2 - 3
-1

julia> -(2, 4.5)
-2.5

-(x, y)

Subtraction operator.

Examples

julia> 2 - 3
-1

julia> -(2, 4.5)
-2.5

-(x, y)

Subtraction operator.

Examples

julia> 2 - 3
-1

julia> -(2, 4.5)
-2.5

com(o1::Operator, o2::Operator; epsilon::Real=0, maxlength::Int=1000)
com(o1::OperatorTS1D, o2::OperatorTS1D; anti=false)

Commutator of two operators. Set anti=true to compute the anti-commutator.

Example

julia> A = Operator(4)
julia> A += "X111"
julia> B = Operator(4)
julia> B += "Z111"
julia> B += "XYZ1"
julia> com(A,B)
(0.0 - 2.0im) Y111

diag(o::Operator)
diag(o::OperatorTS1D)

Diagonal of an operator. Keep the strings that only contain 1's or Z's. Return another operator.

Example

julia> A = Operator(4)
julia> A += 2,"1111"
julia> A += 3,"XYZ1"
julia> A += 3,"Z11Z"
julia> diag(A)
(2.0 + 0.0im) 1111
(3.0 + 0.0im) Z11Z

trace(o::Operator)
trace(o::OperatorTS1D)

Trace of an operator

Example

julia> A = Operator(4)
julia> A += 2,"1111"
julia> A += 3,"XYZ1"
julia> trace(A)
32.0 + 0.0im

opnorm(o::Operator)
opnorm(o::OperatorTS1D)

Frobenius norm

Example

julia> A = Operator(4)
julia> A += 2,"X",2
julia> A += 1,"Z",1,"Z",3
julia> opnorm(A)
8.94427190999916

dagger(o::Operator)
dagger(o::OperatorTS1D)

Conjugate transpose

Example

A = Operator(3)
A += 1im,"X",2
A += 1,"Z",1,"Z",3

julia> A

(1.0 + 0.0im) Z1Z
(0.0 + 1.0im) 1X1


julia> dagger(A)
(1.0 - 0.0im) Z1Z
(0.0 - 1.0im) 1X1

ptrace(o::Operator, keep::Vector{Int})

Partial trace.

keep is list of qubits indices to keep starting at 1 note that this still returns an operator of size N and doesnt permute the qubits this only gets rid of Pauli strings that have no support on keep and add their coeficient*2^N to the identity string

Example

A = Operator(5)
A += "XY1XZ"
A += "XY11Z"

julia> ptrace(A, [3,4])
(1.0 - 0.0im) XY1XZ
(8.0 - 0.0im) 11111

julia> ptrace(A, [1,5])
(1.0 - 0.0im) XY1XZ
(1.0 - 0.0im) XY11Z

Base.:^(o::Operator, k::Int)

kth power of o. Same as oppow.

oppow(o::Operator, k::Int)
oppow(o::OperatorTS1D, k::Int)

kth power of o. Same as ^.

trace_product(o1::Operator, o2::Operator; scale=0)
trace_product(o1::OperatorTS1D, o2::OperatorTS1D; scale=0)

Efficiently compute trace(o1*o2). This is much faster than doing trace(o1*o2). If scale is not 0, then the result is normalized such that trace(identity)=scale.

trace_product(A::Operator, k::Int, B::Operator, l::Int; scale=0)
trace_product(A::OperatorTS1D, k::Int, B::OperatorTS1D, l::Int; scale=0)

Efficiently compute trace(A^k*B^l). This is much faster than doing trace(A^k*B^l).

If scale is not 0, then the result is normalized such that trace(identity)=scale.

trace_product(A::Operator, k::Int; scale=0)

Efficiently compute trace(A^k). This is much faster than doing trace(A^k).

If scale is not 0, then the result is normalized such that trace(identity)=scale.

moments(H::Operator, kmax::Int; start=1, scale=0)
moments(H::OperatorTS1D, kmax::Int; start=1, scale=0)

Compute the first kmax moments of H. start is the first moment to start from.

If scale is not 0, then the result is normalized such that trace(identity)=scale.

rand_local2(N::Int)

Random 1-local operator

rand_local2(N::Int)

Random 2-local operator

rand_local1_TS1D(N::Int)

Random 1-local OperatorTS1D

rand_local2_TS1D(N::Int)

Random 2-local OperatorTS1D

truncate(o::Operator, N::Int; keepnorm::Bool = false)

Remove all terms of length > N. Keep all terms of length <= N. i.e remove all M-local terms with M>N

Example

A = Operator(4)
A += "X",1,"X",2
A += "Z",1,"Z",2,"Z",4

julia> A
(1.0 + 0.0im) ZZ1Z
(1.0 + 0.0im) XX11

julia> ps.truncate(A,2)
(1.0 + 0.0im) XX11

trim(o::Operator, N::Int; keepnorm::Bool = false, keep::Operator=Operator(N))

Keep the first N terms with largest coeficients.

keepnorm is set to true to keep the norm of o.

keep is an operator that specify a set of strings that cannot be removed

Example

A = Operator(4)
A += 1,"XXXX"
A += 2,"XX11"
A += 3,"XX1X"
A += 4,"ZZXX"
B = Operator(4)
B += 1,"XX11"
B += 1,"XX1X"

julia> trim(A,2)
(4.0 + 0.0im) ZZXX
(3.0 + 0.0im) XX1X

julia> trim(A,2;keep=B)
(4.0 + 0.0im) ZZXX
(3.0 + 0.0im) XX1X
(2.0 + 0.0im) XX11

 prune(o::Operator, alpha::Real; keepnorm::Bool = false)

Keep terms with probability 1-exp(-alpha*abs(c)) where c is the weight of the term

cutoff(o::Operator, epsilon::Real; keepnorm::Bool = false)

Remove all terms with weight < epsilon

Example

A = Operator(4)
A += 1,"XXXX"
A += 2,"XX11"
A += 3,"XX1X"
A += 4,"ZZXX"

julia> cutoff(A, 2.5)
(3.0 + 0.0im) XX1X
(4.0 + 0.0im) ZZXX

add_noise(o::Operator, g::Real)

Add depolarizing noise that make the long string decays. g is the noise amplitude.

Example

A = add_noise(A, 0.1)

Reference

https://arxiv.org/pdf/2407.12768

k_local_part(o::Operator, k::Int)

Return the k-local part of o. I.e all the strings of lenght k.

Example

A = Operator(4)
A += "X",1,"X",2
A += "Z",1,"Z",2,"Z",4
A += "1X11"

julia> A
(1.0 + 0.0im) ZZ1Z
(1.0 + 0.0im) 1X11
(1.0 + 0.0im) XX11

julia> k_local_part(A,2)
(1.0 + 0.0im) XX11

lanczos(H::Operator, O::Operator, steps::Int, nterms::Int; keepnorm=true, maxlength=1000)
lanczos(H::OperatorTS1D, O::OperatorTS1D, steps::Int, nterms::Int; keepnorm=true, maxlength=1000)

Computer the first steps lanczos coeficients for Hamiltonian H and initial operator O

At every step, the operator is trimed with trim and only nterms are kept.

Using maxlength speeds up the commutator by only keeping terms of length <= maxlength

lanczos(H::Operator, O::Operator, steps::Int, nterms::Int; keepnorm=true, maxlength=1000)
lanczos(H::OperatorTS1D, O::OperatorTS1D, steps::Int, nterms::Int; keepnorm=true, maxlength=1000)

Computer the first steps lanczos coeficients for Hamiltonian H and initial operator O

At every step, the operator is trimed with trim and only nterms are kept.

Using maxlength speeds up the commutator by only keeping terms of length <= maxlength

rk4(H::Operator, O::Operator, dt::Real; hbar::Real=1, heisenberg=false, M=2^20, keep::Operator=Operator(N))

Single step of Runge–Kutta-4 with time independant Hamiltonian. Returns O(t+dt). Set heisenberg=true for evolving an observable in the heisenberg picture. If heisenberg=false then it is assumed that O is a density matrix.

rk4(H::Function, O::Operator, dt::Real, t::Real; hbar::Real=1, heisenberg=false)

Single step of Runge–Kutta-4 with time dependant Hamiltonian. H is a function that takes a number (time) and returns an operator.

compress(o::Operator)
compress(o::OperatorTS1D)

Accumulate repeated terms and remove terms with a coeficient smaller than 1e-20

op_to_strings(o::Operator)

takes an operator, return (coefs, strings) where coefs is a list of numbers and strings is a list of pauli string coefs[i] multiply strings[i]

op_to_dense(o::Operator)

Convert an operator to a dense matrix.

shift_left(O::Operator)

Shift evey string left so they start on site 1. This usefull for using translation symmetry in 1D systems

Example

A = Operator(4)
A += "XYZ1"
A += "11ZZ"
A += "1XZY"
A += "ZZ11"

julia> shift_left(A)
(1.0 - 0.0im) XZY1
(1.0 - 0.0im) XYZ1
(2.0 + 0.0im) ZZ11