Predefined Models of Quantum States

struct BarrettKokBellPair <: QuantumSavory.StatesZoo.AbstractTwoQubitState

Fields:

• ηᴬ: Individual channel transmissivity from source A to entanglement swapping station, ∈[0,1]

• ηᴮ: Individual channel transmissivity from source B to entanglement swapping station, ∈[0,1]

• Pᵈ: Total excess noise (photons per qubit slot) in photon detectors, ≥0, usually ≪1

• ηᵈ: Detection efficiency of photon detectors, ∈[0,1]

• 𝒱: Mode matching parameter for individual interacting photonic pulses with |V| evaluates mode overlap and arg(V) evaluates the carrier phase mismatch, |V|∈[0,1]

• m: A single parity bit determined by the click pattern (m = 0 for [0, 1, 1, 0] or [1, 0, 0, 1]; m = 1 for [1, 1, 0, 0] or [0, 0, 1, 1])

• metadata

A symbolic representation of the noisy Bell pair state obtained in a Barrett-Kok style protocol (a sequence of two successful entanglement swaps), referred to as the "dual rail photonic qubit swap" in (Prajit Dhara and Guha, 2023) (see eq. C7).

See also BarrettKokBellPairW for the weighted density matrix.

BarrettKokBellPair(ηᴬ,ηᴮ)

Asymmetric noiseless perfectly mode-matched case ηᴬ≠ηᴮ, Pᵈ=0, ηᵈ=1, 𝒱=1, m=0

BarrettKokBellPair(η)

Symmetric noiseless perfectly mode-matched case ηᴬ=ηᴮ=η, Pᵈ=0, ηᵈ=1, 𝒱=1, m=0

The weighted version of BarrettKokBellPair, i.e. its trace is the probability of successfully heralding a Barrett-Kok Bell pair.

struct DepolarizedBellPair <: QuantumSavory.StatesZoo.AbstractTwoQubitState

Fields:

• p: Depolarization parameter p ∈ [0, 1], related to fidelity by F = (3p+1)/4

• metadata

A symbolic representation of the depolarized |Φ⁺⟩ = (|00⟩+|11⟩)/√2 Bell state: p |Φ⁺⟩⟨Φ⁺| + (1-p) I/4

where I/4 is the two-qubit maximally mixed state.

The fidelity F = ⟨Φ⁺|ρ|Φ⁺⟩ relates to the depolarization parameter by:

• F = (3p + 1) / 4
• p = (4F - 1) / 3

Can be constructed from either parameter:

• DepolarizedBellPair(p) — depolarization parameter p ∈ [0, 1]
• DepolarizedBellPair(F=F) — from fidelity F ∈ [1/4, 1]

An interactive explorer for two-qubit states. It returns a new figure.

Requires a Makie plotting backend to be imported.

using GLMakie
using QuantumSavory
using QuantumSavory.StatesZoo
stateexplorer(TheStateTypeYouWant) # an interactive Makie figure will be returned

See also stateexplorer!.

An interactive explorer for two-qubit states. It modifies the given figure.

Requires a Makie plotting backend to be imported.

See also stateexplorer.

Return the "interesting" parameters that a state from the StatesZoo has. A constructor that uses only these parameters needs to exist.

Used by stateexplorer to generate the most valuable plots of figures of merit.

Return the valid ranges and the "good" value for all parameters listed in stateparameters.

struct GenqoMultiplexedCascadedBellPairW <: QuantumSavory.StatesZoo.AbstractTwoQubitState

Fields:

• ηᵇ: Loss (transmissivity) in the Bell state measurement at the source (modes 3, 4, 5, 6), ∈[0,1]

• ηᵈ: Loss (transmissivity) in all of the detectors, ∈[0,1]

• ηᵗ: Outcoupling transmissivity for the bell-state modes (1,2,7,8), ∈[0,1]

• N: Mean photon number per mode of the state. This is a tradeoff parameter for fidelity vs rate. It has to be >0 (but the model becomes imprecise at N>0.2 due to the 2-photon cutoff of the Fock space used in derivation)

• metadata

Heralded multiplexed cascaded source (a.k.a. single mode model for zero added loss multiplexed (ZALM) source).

The state is not normalized and its trace corresponds to the probability of successful heralding.

Based on the cascaded source from (and Guha, 2022) and (and Englund, 2023).

Functions are included for both the photon-photon state as well as the spin-spin state following loading using Duan-Kimble style quantum memories

Implemented as a wrapper around the Genqo.jl package.

struct GenqoUnheraldedSPDCBellPairW <: QuantumSavory.StatesZoo.AbstractTwoQubitState

Fields:

• ηᵈ: Loss (transmissivity) in all of the detectors, ∈[0,1]

• ηᵗ: Outcoupling transmissivity for the bell-state modes (1,2,3,4), ∈[0,1]

• N: Mean photon number per mode of the state. This is a tradeoff parameter for fidelity vs rate. It has to be >0 (but the model becomes imprecise at N>0.2 due to the 2-photon cutoff of the Fock space used in derivation)

• metadata

Unheralded source of polarization Bell pairs, as described by (Kwiat et al., 1995).

Functions are included for both the photon-photon state as well as the spin-spin state following loading using Duan-Kimble style quantum memories

Implemented as a wrapper around the Genqo.jl package.