Apparatus and methods for reduction of crosstalk in integrated photonics …
US20260147154A1
Abstract
Apparatus and method for minimum crosstalk between waveguides via on chip filtering and scatter mitigation necessary to provide tunable addressing of atomic memories. Methods are disclosed to improve the extinction ratio between coherent optical outputs capable of selectively striking a single atom in an array of atoms confined in a trapped memory.
Description (excerpt)
CROSS-REFERENCE TO RELATED APPLICATIONS This application is a continuation of currently pending U.S. Non-Provisional application Ser. No. 18/191,013 filed Mar. 28, 2023. The contents of which is expressly incorporated herein by reference in its entirety. STATEMENT OF GOVERNMENT INTEREST The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment of any royalty thereon. BACKGROUND OF THE INVENTION This invention relates generally to the mitigation of scatter in integrated photonics devices with application to reduction of crosstalk between integrated waveguides and the ability to accurately address quantum memories such as a trapped ion system. OBJECTS AND SUMMARY OF THE INVENTION The present invention provides new design paradigms for integrated photonic devices that reduce the amount of stray light reaching the output facet such that a higher extinction ratio is created between any two outputs. This is critical for the addressing of quantum memories where crosstalk between intended control signals applied to the desired qubits and stray signals effecting other qubits can lead to decoherence and other detrimental effects. Briefly stated the present invention discloses methods to redesign any state-of-the-art integrated photonic chip for the desired outcome of reducing cross talk as measured between waveguides spaced such to address a quantum memory system such as but not limited to trapped ions. The invention's methods are not limited to quantum memory applications and can be used similarly to reduce photon induced quasi-particle poisoning in superconducting devices among other applications. A preferred embodiment of the present invention consists of a Silicon Nitride (SiN) integrated photonic device (also called the chip herein), which can be made compatible with CMOS fabrication methods, consisting of a plurality of waveguides carrying a plurality of wavelengths for the purpose of trapping, addressing and controlling atomic memories. Such waveguides may collect, emit, split, combine, route, distribute, intensity modulate, phase modulate, polarization rotate, or all of the above, the carried light. The preferred embodiment is described in terms of SiN waveguides, but any integrated optical platform such as Silicon on Insulator (SoI), Lithium Niobate (LiNbO), or Aluminum Nitride (AIN) among others can be substituted. The wavelengths used are dependent on the type of memory and can altered. The preferred embodiment described herein assumes a plurality of wavelengths for trapping and controlling a plurality of barium ions, but other quantum memories can be substituted. On chip scattering has several sources that lead to crosstalk and background modes of propagation on the chip, also known as slab modes. These stray photons can have detrimental effects on the system by acting as background photons, thus reducing the extinction ratio for the optical laser fields that control a quantum memory. The preferred embodiment of the present invention comprises a trapped ion system such as singly ionized Barium 133. Other ionizations or atomic species such as Ytterbium, Barium, Rubidium or Calcium among others or mixtures of such species and ionizations represent minor changes. Each ion in the trap is held in close proximity to its nearest neighbor, usually in a chainlike configuration. The desired delivery system for laser light is such that a single ion is strongly illuminated while no other ion receives any stray light. This implies an extinction ratio of 100% or equivalently zero crosstalk. Such an extinction ratio is not producible in any physical system due to realistic physical properties. However, the goal of maximizing the extinction ratio or equivalently reducing the crosstalk between closely spaced optical beams or waveguides remains an open problem in the state of the art. This high extinction ratio includes the desired wavelengths for controlling the quantum memory as well as removing undesired wavelengths such pump wavelengths for non-linear optics. Spontaneous parametric down conversion (SPDC), second harmonic generation (SHG) or other non-linear processes can be performed (not depicted) to obtain photons at a desired wavelength. As an example, but not limited to, SPDC from 775 to produce 1550 nm photons. Depending on the material of the chip this can be performed on or off chip by industry standard methods. This can lead to an additional requirement for addressing quantum memories. The pump photons at the undesired wavelength, in our example the 775 nm photons, need to be filtered out of the waveguides to an extremely high degree of approximately −140 dBm. This refers not just to the slab modes around the waveguide but to 775 nm photons that propagate in the waveguides to the output facet. The presen
Filing details
- Inventors
- Michael L. Fanto
- Assignee
- Government Of The United States As Represented By The Secretary Of The Air …
- Filed
- Oct 20, 2025
- Granted
- Application pending
Bibliographic data and excerpted text sourced from Google Patents (public record) as part of IP TechMatch's current-filings monitor. This filing is not part of the 2019 historical archive. For the authoritative full text, drawings, and legal status, see the source links above or consult USPTO records directly.