Description:FORM 2

THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003

COMPLETE SPECIFICATION
(See section 10, rule 13)

“A SYSTEM FOR POLARIZATION BASED TOPOLOGICAL PHOTON DETECTION AND METHOD THEREOF”

Indian Institute of Technology, Mandi, of IP & TT Cell, SRIC Office, IIT Mandi, Kamand, Himachal Pradesh 175005, India,

The following specification particularly describes the invention and the manner in which it is to be performed.

 
CROSS-REFERENCE TO RELATED APPLICATIONS AND PRIORITY
[01] The present application does not claim priority from any application.

TECHNICAL FIELD
[02] The present invention relates generally to the field of single-photon detection, quantum photonics, and optical measurement systems. More particularly, the invention pertains to a phase-correlated Single-Photon Avalanche Diode (SPAD) based detection architecture configured for polarization-resolved photon detection and topology-linked photon state inference.

BACKGROUND
[03] Single-photon detection forms the backbone of modern quantum optics, quantum communication, and advanced photonic measurement systems. Among various detector technologies, Single-Photon Avalanche Diodes (SPADs) are widely utilized due to their high detection efficiency, compact structure, and capability to operate at room temperature. Conventional SPAD-based systems, particularly those used in time-correlated single-photon counting (TCSPC), primarily measure photon arrival time and intensity. However, these systems treat photon detection events as statistically independent and do not preserve phase relationships or inter-channel correlations, limiting their ability to extract deeper physical properties of light.
[04] Recent developments in structured light and topological photonics have demonstrated that photons can carry additional information through properties such as orbital angular momentum, geometric phase, and topology-protected states. These properties are highly robust against environmental perturbations and are increasingly important in quantum communication, sensing, and information processing applications. However, existing techniques for detecting such topology-linked photon characteristics rely heavily on interferometric setups, spatial mode decomposition, and phase-sensitive optical components. These methods are inherently complex, sensitive to noise, and require precise alignment and controlled environments, making them difficult to scale and deploy in practical systems.
[05] Further, conventional polarization-resolved SPAD systems lack the ability to maintain phase coherence across multiple detection channels. Additionally, many existing systems depend on full quantum state tomography, which is computationally intensive and impractical for real-time or high-throughput applications.

SUMMARY
[06] Before the present system for polarization based topological photon detection and method thereof, are described, it is to be understood that this application is not limited to the particular devices, and methodologies described, as there can be multiple possible embodiments which are not expressly illustrated in the present disclosure. It is also to be understood that the terminology used in the description is for the purpose of describing the particular versions or embodiments only, and is not intended to limit the scope of the present application. This summary is provided to introduce concepts related to the system for polarization based topological photon detection and the method thereof are further described below in the detailed description. This summary is not intended to identify essential features of the claimed subject matter nor is it intended for use in determining or limiting the scope of the claimed subject matter.
[07] In one implementation a system for polarization based topological photon detection is disclosed. The system comprising an optical input module is configured to transmit incident photons to Single Photon Avalanche Diode (SPAD) Detectors via Division-of-Focal-Plane (DoFP) Polarization Filter or Polarization Beam Splitter (PBS), the SPDA detectors each comprises SPDA and an avalanche event detected by the SPDA once the incident photon hits the SPDA detector. The system comprising a phase-coherent timing module is configured to assign synchronized timestamps to the avalanche events to polarization channels. The system comprising a polarization analysis module is configured to analyze temporal correlations between the avalanche events across the polarization channels. The system comprising an inference module is configured to extract topology-linked photon output based on a temporal correlation data and a polarization correlation data.
[08] In another implementation, a method of polarization based topological photon detection. The method comprises a step of directing incident photons received from an optical input module towards Single Photon Avalanche Diode (SPAD) detector via a Division-of-Focal-Plane (DoFP) Polarization Filter or a Polarization Beam Splitter (PBS). The method comprises a step of detecting an avalanche event by the SPDA. The avalanche events get generated when a photon hits the SPDA detector. The method comprises a step of quenching and resetting the single photon avalanche diode by using quenching and reset circuit. The method comprises a step of analyzing topology-linked photon output through an inference module.

BRIEF DESCRIPTION OF THE DRAWINGS
[09] The foregoing detailed description of embodiments is better understood when read in conjunction with the appended drawings. For the purpose of illustrating the disclosure, example constructions of the disclosure are shown in the present document; however, the disclosure is not limited to the specific methods and systems disclosed in the document and the drawings.
[10] The detailed description is given with reference to the accompanying figures. In the figures, the left-most digit(s) of a reference number identify the figure in which the reference number first appears. The same numbers are used throughout the drawings to refer like features and components.
[11] Figure 1 illustrates a block diagram of a system for polarization based topological photon detection, in accordance with an embodiment of the present subject matter;
[12] Figure 2A illustrates block diagrams of polarization by using a division-of-focal-plane (DoFP) polarization filter, in accordance with an embodiment of the present subject matter;
[13] Figure 2B illustrates block diagrams of polarization by using a polarization beam splitter, in accordance with an embodiment of the present subject matter;
[14] Figure 3 illustrates details of a phase-coherent timing module, in accordance with an embodiment of the present subject matter;
[15] Figure 4A illustrates schematic of a polarization-resolved photon detection and topology-linked inference workflow, in accordance with an embodiment of the present subject matter;
[16] Figure 4B illustrates exemplary schematic of the polarization-resolved single-photon detection and topology-linked inference workflow in accordance with an embodiment of the present subject matter;
[17] Figure 5 illustrates of a topology-to-polarization mapping schematic for topology-linked photon detection, in accordance with an embodiment of the present subject matter;
[18] Figure 6 illustrates a camera implementation configured for parallel topology-linked photon detection, in accordance with an embodiment of the present subject matter; and
[19] Figure 7 illustrates a method of polarization based topological photon detection, in accordance with an embodiment of the present subject matter.

DETAILED DESCRIPTION
[20] Some embodiments of this disclosure, illustrating all its features, will now be discussed in detail. The words "comprising," "having," "containing," and "including," and other forms thereof, are intended to be equivalent in meaning and be open ended in that an item or items following any one of these words is not meant to be an exhaustive listing of such item or items, or meant to be limited to only the listed item or items. It must also be noted that as used herein and in the appended claims, the singular forms "a," "an," and "the" include plural references unless the context clearly dictates otherwise. Although any device and methods similar or equivalent to those described herein can be used in the practice or testing of embodiments of the present disclosure, the exemplary, a system for polarization based topological photon detection and method thereof are now described. The disclosed embodiments are merely exemplary of the disclosure, which may be embodied in various forms.
[21] Various modifications to the embodiment will be readily apparent to those skilled in the art and the generic principles herein may be applied to other embodiments. However, one of ordinary skill in the art will readily recognize that the present disclosure for the system for polarization based topological photon detection and method thereof is not intended to be limited to the embodiments illustrated, but is to be accorded the widest scope consistent with the principles and features described herein.
[22] The present subject discloses a system for polarization based topological photon detection and method thereof. Figure 1 illustrates a block diagram of the system (100) for polarization based topological photon detection. The system (100) comprising an optical input module (200) is configured to transmit incident photons to Single Photon Avalanche Diode (SPAD) Detectors (400) via Division-of-Focal-Plane (DoFP) Polarization Filter (300 A) or Polarization Beam Splitter (PBS) (300 B). The SPAD detectors (400A, B) each comprises SPDA and an avalanche event detected by the SPAD once the incident photon hits the SPAD detector (400). When a photon hits the SPAD a large avalanche current gets generated i.e., a photon is detected.
[23] The SPAD Detectors (400) each comprises Single Photon Avalanche Diode operated in a geiger mode and configured to detect the incident photons. The SPAD Detectors (400) each comprises quenching and reset circuit (402) configured to quench the large avalanche current which reduces a voltage below breakdown level and reset (i.e., the voltage is restored) the single photon avalanche diode upon detection of the avalanche events by the SPAD detectors (400A, 400B).
[24] Further, The SPAD detectors (400A, 400B) are configured to detect phase-dependent intensity variations, orbital angular momentum, vortex core displacement, phase singularity transitions, and symmetry-dependent intensity distributions of the incident photons.
[25] The SPAD detectors (400A, 400B) configured to provide the detected the avalanche event (i.e., signals) to a phase-coherent timing module (500). The phase-coherent timing module (500) is configured to assign synchronized timestamps to the avalanche events to polarization channels. The polarization channels get already generated after passing through DoFP filters (300 A) or PBS (300 B). Further, the phase-coherent timing module (500) also receives topology-to-polarization mapping signals from a topology-to-polarization mapping module (202). The topology-to-polarization mapping module (202) receives input from the Optical Input Module (200).
[26] The system (100) comprising a polarization analysis module (600) is configured to analyse temporal correlations between the avalanche events across the polarization channels. an inference module (700) is configured to extract topology-linked photon output (800) based on a temporal correlation data and a polarization correlation data. The temporal correlation data is derived from the synchronized timestamps of the avalanche events and the polarization correlation data is outcome of a topology-to-polarization mapping module (202). The inferred topology-linked photon outputs (800) include orbital angular momentum signatures, geometric phase-related features, winding number-related characteristics and symmetry-dependent intensity variations.
[27] Now referring to Figure 2A illustrates block diagrams of polarization using a division-of-focal-plane (DoFP) polarization filter. An embodiment is realized in an array of SPAD detectors (400A, B, C) or camera configuration. In the embodiment, the DoFP polarization filter (300A) is integrated with the array of SPAD detectors (400 A, 400B, 400C) pixels, where each pixel acts as an individual SPAD detectors (400A, B, C) elements in a spatial array, each associated with the DoFP polarization filter arrangement for resolving different polarization states at different spatial locations.
[28] Now in an alternative embodiment of polarization, Figure 2B illustrates block diagrams of polarization by using a polarization beam splitter. An optical coupling interface (300B1) is integrated in between the optical input module (200) and the PBS (300 B), which separates orthogonal polarization components and directs such components to separate SPAD detectors (400 A, 400B) (herein also referred as channels). As an example, the optical interface (300B1) is provided to accept free-space structured light or fiber-guided photons. Electromagnetic shielding and noise isolation layers are incorporated to suppress thermal and electronic noise, ensuring accurate photon detection aligned with the photon generation region.
[29] Figure 3 illustrates details of a phase-coherent timing module (500). A shared reference clock (502) is distributed to multiple time-tagging units (504A, 504B) associated with corresponding the SPAD detectors (400A, 400B) to time-stamp the avalanche events. The SPDA detectors (400A, B) provides input to the time tagging unit (504) in form of photon events (i.e., avalanche events). The SPAD detector (400A) defines a first polarization-resolved detection channel and the SPAD detector (400B) defines a second polarization-resolved detection channel. Per-channel timing offsets are compensated using a timing offset calibration unit (506) to ensure phase-comparable timing data across polarization-resolved detection channels.
[30] Figure 4A illustrates schematic of a polarization-resolved photon detection and topology-linked inference workflow. the SPAD detectors (400A, 400B) capture the incident photons for two polarization channels, generating the temporal correlation data (i.e., a time-tagged photon detection data). The polarization correlation data (which is outcome of a topology-to-polarization mapping module (202)) are extracted by the polarization analysis module (600) and analyzed through an inter-channel temporal correlator (602) of the interface module (700), including cross-correlation, delay compensation, and coherence metrics. The resulting correlation features feed into a topology-linked inference engine (702) to generate topology-linked invariant photon outputs, providing robust photon-based observables for downstream analysis. The inferred topology-linked photon outputs (800) include orbital angular momentum signatures, geometric phase-related features, winding number-related characteristics and symmetry-dependent intensity variations.
[31] The orbital angular momentum (OAM) signatures refer to distinctive photon properties associated with helical or twisted wavefronts, where a light carries angular momentum due to its spatial phase structure. Such signatures enable identification of vortex beams and structured light modes based on their rotational phase characteristics. The geometric phase-related features arise from phase changes accumulated due to the evolution of the photon’s polarization or path, rather than physical distance traveled. They provide robust, invariant information that remains stable under environmental disturbances and optical phase fluctuations. The winding number-related characteristics describe a number of times the optical phase wraps around a singularity point in a structured light field. The winding number is used to quantify topological properties of photons, such as vortex order and phase rotation behavior. The symmetry-dependent intensity variations refer to spatial intensity patterns of light that depend on a symmetry of an optical field or photon structure. Such variations help identify underlying photon states by analyzing how intensity is distributed across different spatial or polarization configurations.
[32] Figure 4B illustrates exemplary schematic of the polarization-resolved single-photon detection and topology-linked inference workflow. The incident photons are detected simultaneously in two orthogonal polarization channels (H and V) using the single-photon avalanche diode (SPAD) detectors (400A, 400B), generating time-tagged photon arrival sequences for each polarization. These time-resolved detection streams are processed to extract polarization observables by polarization analysis module (600) through the inter-channel temporal correlator (602), including cross-correlation between polarization channels, temporal delay compensation to correct channel-dependent offsets, and coherence-based metrics to quantify polarization-dependent photon correlations. The resulting correlation features are aggregated and passed to a topology-linked inference engine (702) which is part of the interface module (700), where relational and invariant structures in the photon correlation space are identified. This inference stage produces topology-linked invariant photon outputs that are robust against noise, timing jitter, and polarization fluctuations, enabling stable photon-based observables for downstream physical, biological, or information-processing analyses. The phase-coherent timing module (500) is configured to provide shared clock within the system (100).
[33] Figure 5 illustrates of a topology-to-polarization mapping schematic for topology-linked photon detection using phase-correlated single-photon avalanche diode (SPAD) detectors (400A,400B). The optical input module (200) (herein also referred as a topology-linked structured photon source) (1) is processed through the topology-to-polarization mapping module (202), generating an incident photon wavefront (3) that is separated by a polarization analysis element (4) into orthogonal polarization components. The horizontally polarized component is detected by a first SPAD detector (400A), and the vertically polarized component is detected by a second SPAD detector (400B), both synchronized through the shared phase-coherent timing and correlation link provided by the phase-coherent timing module (500). The correlated polarization observation (602) is generated by the polarization analysis module (600) from time-synchronized and timing-offset-compensated avalanche events obtained from the SPAD detectors (400A, 400B), enable inference of topology-linked photon outputs. Further, a phase-comparable detection events defined as processed avalanche events from the SPAD detectors (400A, 400B).
[34] Figure 6 illustrates a camera (300 A1) implementation for parallel topology-linked photon detection. A topology-linked structured photon field originating from the optical input module (200) and by the topology-to-polarization mapping module (202) (herein also refer as a photon source) is processed through polarization analysis elements and incident on a plurality of SPAD detection pixels arranged in a SPAD array or the camera (300 A1) each pixel comprises a polarization-resolved SPAD detection channel. The SPAD array or the camera (300 A1) is coupled to integrated phase-coherent timing module (500) configured to provide synchronized time-tagging across all polarization channels. Spatially distributed photon detection events are processed in parallel by topology-linked interference engine (702) and inter-channel temporal correlator (602) to generate the topology-linked photon output (800) derived from polarization-resolved, phase-correlated photon data.
[35] Now, referring to a Figure 7 which illustrates a method (900) for polarization based topological photon detection in accordance with an embodiment of the present subject matter. The order in which the method (900) is described is not intended to be construed as a limitation, and any number of the described method blocks can be combined in any order to implement the method (900) or alternate methods. Additionally, individual blocks may be deleted from the method (900) without departing from the spirit and scope of the subject matter described herein. For ease of explanation, in the embodiments described below, the method (900) may be considered for polarization based topological photon detection using the system (100).
[36] At step (902): The method (1100) comprises directing incident photons received from an optical input module (200) towards Single Photon Avalanche Diode (SPAD) detector (400) via a Division-of-Focal-Plane (DoFP) Polarization Filter (300 A) or a Polarization Beam Splitter (PBS) (300 B).
[37] At step (904): The method (1100) comprises detecting an avalanche event generated by the SPDA (400), the avalanche events get generated when a photon hits the SPDA detector (400).
[38] At step (906): The method (1100) comprises quenching and resetting the single photon avalanche diode by using quenching and reset circuit (402).
[39] At step (908): The method (1100) comprises Analysing, topology-linked photon output (characteristics) (800) through an inference module (700).
[40] The method (900) may be read along with suitable embodiments and exemplary embodiments of the system (100) and aforesaid mentioned embodiments are suitably applicable to method (900).
[41] The system (100) and method (900) may be used in quantum communication systems, including quantum key distribution (QKD) receivers, as well as in optical quantum computing and quantum state verification modules.
[42] The system (100) and method (900) may be used in quantum sensing, precision optical measurement, and real-time correlation-based photon analysis applications.
[43] The system (100) and method (900) may be used for topological photonics characterization, structured light analysis, and detection of optical vortex and orbital angular momentum (OAM) states.
[44] The system (100) and method (900) may be used in time-resolved single-photon imaging, LiDAR systems, and integrated SPAD arrays or single-photon camera technologies.
[45] The system (100) and method (900) may be used for polarization-resolved photon detection and noise-resilient photonic measurements under ambient and non-ideal operating conditions.
[46] The system (100) provides a significant technical advancement over conventional single-photon detection systems by introducing a phase-coherent, polarization-resolved SPAD-based architecture capable of extracting correlation-based and topology-linked photon information without relying on interferometric techniques or cryogenic operation. Unlike traditional SPAD systems that are limited to independent photon counting and intensity measurements, the system (100) enables synchronized time-stamping across multiple polarization channels, thereby facilitating inter-channel temporal correlation and invariant feature extraction. Aforesaid advancement allows indirect inference of phase-related and topological photon characteristics, such as geometric-phase proxies and orbital-angular-momentum-linked signatures, using only polarization and timing data. As a result, the system (100) enhances robustness against optical phase drift, environmental noise, and intensity fluctuations while maintaining room-temperature operability. Furthermore, the architecture supports scalable and modular integration into multi-channel photonic systems, enabling real-time quantum verification, structured photon detection, and topology-aware measurement in practical and non-ideal environments.
[47] The above are only preferred embodiments of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should be regarded as the protection scope of the present invention.
, Claims:WE CLAIM:

1. A system (100) for polarization based topological photon detection, the system (100) comprising:
an optical input module (200) is configured to transmit incident photons to Single Photon Avalanche Diode (SPAD) detectors (400) via Division-of-Focal-Plane (DoFP) Polarization Filter (300 A) or Polarization Beam Splitter (PBS) (300 B), wherein the SPDA detectors (400) each comprises SPDA and an avalanche event detected by the SPDA once the incident photon hits the SPDA detector (400);
a phase-coherent timing module (500) is configured to assign synchronized timestamps to the avalanche events to polarization channels, wherein the polarization channels get already generated after passing through DoFP filters (300 A) or PBS (300 B);
a polarization analysis module (600) is configured to analyse temporal correlations between the avalanche events across the polarization channels; and
an inference module (700) is configured to extract topology-linked photon output (800) based on a temporal correlation data and a polarization correlation data.

2. The system (100) as claimed in claim 1, wherein the SPAD Detectors (400) each comprises Single Photon Avalanche Diode operated in a geiger mode and configured to detect the incident photons.

3. The system (100) as claimed in claim 1, wherein the inferred topology-linked photon outputs (800) include orbital angular momentum signatures, geometric phase-related features, winding number-related characteristics and symmetry-dependent intensity variations.

4. The system (100) as claimed in claim 1, wherein the temporal correlation data is derived from the synchronized timestamps of the avalanche events and the polarization correlation data is outcome of a topology-to-polarization mapping module (202).

5. The system (100) as claimed in claim 1, wherein the SPAD each comprises quenching and reset circuit (402) configured to quench and reset the single photon avalanche diode upon detection of the avalanche events by SPAD detectors (400A, 400B).

6. The system (100) as claimed in claim 1, wherein the SPAD detectors (400A, 400B) are configured to detect phase-dependent intensity variations, orbital angular momentum, vortex core displacement, phase singularity transitions, and symmetry-dependent intensity distributions of the incident photons.

7. A method (900) of polarization based topological photon detection, the method (900) comprising:
directing (902), incident photons received from an optical input module (200) towards Single Photon Avalanche Diode (SPAD) detector (400) via a Division-of-Focal-Plane (DoFP) Polarization Filter (300 A) or a Polarization Beam Splitter (PBS) (300 B);
detecting (904), an avalanche events by the SPDA (400), wherein the avalanche events get generated when a photon hits the SPDA detector (400);
quenching and resetting (906) the single photon avalanche diode by using quenching and reset circuit (402); and
analysing (908), topology-linked photon output (800) through an inference module (700).