Two-photon quantum state engineering in nonlinear photonic nanowires

Abstract

We propose and analyze a generic technique to engineer the two-photon quantum state generated by spontaneous parametric downconversion (SPDC) in nonlinear photonic nanowires using any suitable material system. Through dispersion engineering in nanowires, the group velocity of each photon involved in the SPDC process can be tuned such that pure heralded single photons or maximally polarization entangled photons can be directly generated on a chip. Implementations in III-V semiconductor and ferroelectric waveguides demonstrate minimal frequency correlations with Schmidt numbers of ∼1 for heralded single photons, and maximal entanglement with concurrences of ∼1 for polarization entangled photons.

Uncovering dispersion properties in semiconductor waveguides to study photon-pair generation

“…In other words, at least one of the interacting modes is a higher order mode [26,27]. Even though accurate measurements of the refractive index of bulk AlGaAs exist [28], the effective indices of different spatial modes propagating in BRWs can usually be investigated only numerically [29][30][31]. While the refractive index can be simulated quite accurately, the group index calculated from these models can be far off from the true experimental value.…”

Lithium Niobate on Insulator: An Emerging Platform for Integrated Quantum Photonics

“…In LNOI, the degrees of freedom offered by nanostructuring can be fully exploited for controlling the properties of the generated quantum state, for example, its spatial [66,73] and spectral composition. [67,109] Whereas photon pairs are the basis for quantum applications in quantum cryptography, imaging, [110] and some implementations of photonic quantum computation algorithms, [111] sources of pure single photons are needed for universal quantum computing. [112] Pure single photons can be generated with photon-pair sources using heralding, [113][114][115] where only one of the photons of a pair is used as a quantum resource, whereas the other heralds the presence of this resource.…”

“…In LNOI, the degrees of freedom offered by nanostructuring can be fully exploited for controlling the properties of the generated quantum state, for example, its spatial [ 66,73 ] and spectral composition. [ 67,109 ]…”

Deterministic separation of arbitrary photon pair states in integrated quantum circuits

“…This effect is shown in Figure 11; as the state's spectral entanglement and hence Schmidt Number is increased, P S is asymptotically restored towards unity through increases in P 0 S and P I S . In SPDC, spectral entanglement depends partly on the dispersion properties of the source [16,17]. However, it is generally dominated by the amount of wavelength anti-correlation imparted by the pump bandwidth.…”