Merge pull request #92 from hongyehu/main

Add Rydberg atom chain quantum system

src/quantum_system_templates/_quantum_system_templates.jl

@@ -3,12 +3,14 @@ module QuantumSystemTemplates
 export TransmonSystem
 export TransmonDipoleCoupling
 export MultiTransmonSystem
+export RydbergChainSystem
 
 using ..QuantumUtils
 using ..QuantumSystems
 
 using LinearAlgebra
 
 include("transmons.jl")
+include("rydberg.jl")
 
 end

src/quantum_system_templates/rydberg.jl

@@ -0,0 +1,91 @@
+@doc raw"""
+    RydbergChainSystem(;
+        C::Float64=862690*2π,  
+        distance::Float64=10.0, # μm
+        cutoff_order::Int=2, # 1 is nearest neighbor, 2 is next-nearest neighbor, etc.
+        local_detune::Bool=false, # If true, include one local detuning pattern.
+    ) -> QuantumSystem
+
+Returns a `QuantumSystem` object for the Rydberg atom chain in the spin basis
+    |g⟩ = |0⟩ = [1, 0], |r⟩ = |1⟩ = [0, 1].
+
+```math
+H = \sum_i 0.5*\Omega_i(t)\cos(\phi_i(t)) \sigma_i^x - 0.5*\Omega_i(t)\sin(\phi_i(t)) \sigma_i^y - \sum_i \Delta_i(t)n_i + \sum_{i<j} \frac{C}{|i-j|^6} n_i n_j
+```
+
+
+# Keyword Arguments
+- `C`: The Rydberg interaction strength in MHz*μm^6.
+- `distance`: The distance between atoms in μm.
+- `cutoff_order`: Interaction range cutoff, 1 is nearest neighbor, 2 is next nearest neighbor.
+- `local_detune`: If true, include one local detuning pattern.
+"""
+function generate_pattern(N::Int, i::Int)
+    # Create an array filled with 'I'
+    qubits = fill('I', N)
+    # Insert 'n' at position i and i+1, ensuring it doesn't exceed the array bounds
+    if i <= N && i+1 <= N
+        qubits[i] = 'n'
+        qubits[i+1] = 'n'
+    end
+    return join(qubits)
+end
+function generate_pattern_with_gap(N::Int, i::Int, gap::Int)
+    # Create an array filled with 'I'
+    qubits = fill('I', N)
+    # Insert 'n' at position i and i+gap+1, ensuring it doesn't exceed the array bounds
+    if i <= N && i+gap+1 <= N
+        qubits[i] = 'n'
+        qubits[i+gap+1] = 'n'
+    end
+    return join(qubits)
+end
+"""
+Embed a character into a string at a specific position.
+"""
+function lift(x::Char,i::Int, N::Int)
+    qubits = fill('I', N)
+    qubits[i] = x
+    return join(qubits)
+end
+
+function RydbergChainSystem(;
+    N::Int=3, # number of atoms
+    C::Float64=862690*2π,  
+    distance::Float64=10.0, # μm
+    cutoff_order::Int=1, # 1 is nearest neighbor, 2 is next-nearest neighbor, etc.
+    local_detune::Bool=false,
+)
+    PAULIS = Dict("I" => [1 0; 0 1], "X" => [0 1; 1 0], "Y" => [0 -im; im 0], "Z" => [1 0; 0 -1], "n" => [0 0; 0 1])
+    if cutoff_order == 1
+        H_drift = sum([C*kron_from_dict(generate_pattern(N,i),PAULIS)/(distance^6) for i in 1:N-1])
+    elseif cutoff_order == 2
+        H_drift = sum([C*kron_from_dict(generate_pattern(N,i),PAULIS)/(distance^6) for i in 1:N-1])
+        H_drift += sum([C*kron_from_dict(generate_pattern_with_gap(N,i,1),PAULIS)/((2*distance)^6) for i in 1:N-2])
+    else
+        error("Higher cutoff order not supported")
+    end
+    H_drives = Matrix{ComplexF64}[]
+    # Add global X drive
+    Hx = sum([0.5*kron_from_dict(lift('X',i,N), PAULIS) for i in 1:N])
+    push!(H_drives, Hx)
+    # Add global Y drive
+    Hy = sum([0.5*kron_from_dict(lift('Y',i,N), PAULIS) for i in 1:N])
+    push!(H_drives, Hy)
+    # Add global detuning
+    H_detune = -sum([kron_from_dict(lift('n',i,N), PAULIS) for i in 1:N])
+    push!(H_drives, H_detune)
+    params = Dict{Symbol, Any}(
+        :N => N,
+        :C => C,
+        :distance => distance,
+        :cutoff_order => cutoff_order,
+        :local_detune => local_detune,
+    )
+    return QuantumSystem(
+        H_drift,
+        H_drives;
+        constructor=RydbergChainSystem,
+        params=params,
+    )
+end