AbstractQuantumGate

AbstractQuantumGate

Abstract type for quantum gates in the quantum circuit representation. Provides common interfaces between ITensors calcurations and quantikz representations. Available gates in ITensor Library

ControlledGate(control::Int, target::Int, gate_type::Symbol)

Two-qubit controlled gate without parameters. gate_type specifies the operation applied to the target qubit. Available types include:

• :CNOT: Controlled-NOT gate (alias: :CX)
• :CY, :CZ: Controlled-Y and Controlled-Z gates
• :CPHASE: Controlled-Phase gate

FourQubitGate(qubit1::Int, qubit2::Int, qubit3::Int, qubit4::Int, gate_type::Symbol)

Four-qubit gate acting on the specified qubits. Available gate_type include:

• :CCCNOT: Triple-controlled NOT gate

MultiQubitGate(qubits::Vector{Int}, gate_type::Symbol)

General n-qubit gate acting on an arbitrary number of qubits. This allows for gates acting on more than 4 qubits or custom multi-qubit operations.

Fields

• qubits::Vector{Int}: Vector of qubit indices (1-based) that the gate acts on.
• gate_type::Symbol: The type of gate to apply.

Examples

# 5-qubit controlled gate
gate = MultiQubitGate([1, 2, 3, 4, 5], :C4NOT)

# Custom multi-qubit gate
gate = MultiQubitGate([1, 3, 5, 7], :CustomGate)

Notes

• The interpretation of gate_type depends on the number of qubits and the specific gate.
• For standard gates with 1-4 qubits, prefer using the specific gate types for clarity.
• This is useful for gates with 5 or more qubits, or for custom multi-qubit operations.

ParametricControlledGate(control::Int, target::Int, gate_type::Symbol, params::Vector{Float64})

Two-qubit controlled gate with parameters. Available gate_type include:

• :CRx, :CRy, :CRz: Controlled rotation gates (argument: [θ])
• :CRn: Controlled rotation about an arbitrary axis (arguments: [θ, ϕ, λ])

ParametricMultiQubitGate(qubits::Vector{Int}, gate_type::Symbol, params::Vector{Float64})

General n-qubit parametric gate acting on an arbitrary number of qubits with parameters.

Fields

• qubits::Vector{Int}: Vector of qubit indices (1-based) that the gate acts on.
• gate_type::Symbol: The type of gate to apply.
• params::Vector{Float64}: Parameters for the gate (e.g., rotation angles).

Examples

# Multi-qubit rotation gate
gate = ParametricMultiQubitGate([1, 2, 3], :MultiRz, [π/4])

# Custom parametric gate
gate = ParametricMultiQubitGate([1, 3, 5], :CustomRotation, [π/2, π/4, π/8])

ParametricSingleGate(qubit::Int, gate_type::Symbol, params::Vector{Float64})

Quantum gate acting on a single qubit with one or more parameters. params is a vector of parameters such as rotation angles (e.g., $\theta, \phi, \lambda$). Available gate_type include:

• :Rx, :Ry, :Rz: Rotation gates around the x, y, and z axes (argument: [θ])
• :Rn: Rotation about an arbitrary axis $n=(\theta, \phi, \lambda)$ (arguments: [θ, ϕ, λ])

ParametricTwoQubitGate(qubit1::Int, qubit2::Int, gate_type::Symbol, params::Vector{Float64})

Two-qubit gate with parameters, typically used for coupling operations. Available gate_type include:

• :Rxx, :Ryy, :Rzz: Ising (XX, YY, ZZ) coupling gates (argument: [ϕ])

QuantumCircuit

Represents a quantum circuit consisting of a fixed number of qubits and a sequence of gates.

Fields

• nqubits::Int: The total number of qubits in the circuit.
• gates::Vector{AbstractQuantumGate}: A list of quantum gates to be applied sequentially.
• initial_states::Vector{AbstractInitialState}: Initial state specification for each qubit. Defaults to [BasisState("0")] for all qubits if not specified.

Initial States Usage

The initial_states field can be specified in two ways:

1. Single state for all qubits: Use a vector with one element

   initial = AbstractInitialState[BasisState("0")]  # All qubits in |0⟩
   initial = AbstractInitialState[ProductState(["0", "1", "+"])]  # Qubits in |0⟩, |1⟩, |+⟩

2. Per-qubit states: Use a vector with one element per qubit

   initial = AbstractInitialState[BasisState("0"), BasisState("1")]  # First qubit |0⟩, second |1⟩

Note: ProductState should be used as a single element, not within a multi-element vector.

SingleQubitGate(qubit::Int, gate_type::Symbol)

Quantum gate acting on a single qubit without parameters. gate_type specifies the type of gate. Available types include:

• :X, :Y, :Z: Pauli operators
• :H: Hadamard gate
• :S, :T: Phase shift gates (aliases: :Phase, :π/8)
• :Proj0, :Proj1: Projection operators ($|0\rangle\langle0|$ and $|1\rangle\langle1|$)

ThreeQubitGate(qubit1::Int, qubit2::Int, qubit3::Int, gate_type::Symbol)

Three-qubit gate acting on the specified qubits. Available gate_type include:

• :Toffoli: Controlled-Controlled-NOT gate (aliases: :CCNOT, :CCX)
• :Fredkin: Controlled-SWAP gate (alias: :CSWAP)

TwoQubitGate(qubit1::Int, qubit2::Int, gate_type::Symbol)

Two-qubit gate without a specific control/target structure. Available gate_type include:

• :SWAP: Swap gate
• :iSWAP: Imaginary Swap gate
• :√SWAP: Square root of Swap gate

add_gate!(circuit::QuantumCircuit, gate::AbstractQuantumGate)

Appends a quantum gate to the end of the circuit's gate sequence. Returns the modified QuantumCircuit object to allow for method chaining.

set_state!(circuit::QuantumCircuit, initial_states::Vector{AbstractInitialState})

Sets the initial state of the quantum circuit. This replaces any existing initial state specification. Returns the modified QuantumCircuit object to allow for method chaining.