Description:FORM 2

THE PATENTS ACT, 1970
(39 OF 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, Rule 13]

TITLE OF INVENTION
QUANTUM ILLUMINATION AND ESTIMATION OF OBJECT REFLECTIVITY USING POLARIZATION-ENTANGLED PHOTON PAIRS

APPLICANT DETAILS
Applicant : INDIAN INSTITUTE OF SCIENCE
Nationality : INDIAN
Address: C V RAMAN AVENUE, BANGALORE 560012, INDIA.

PREAMBLE TO THE DESCRIPTION
The following complete specification particularly describes the invention and the manner in which it is to be performed.

FIELD OF THE INVENTION
Embodiments of the present disclosure relate to a Quantum Illumination method and system with polarization-entangled photon pairs using CHSH value corresponding to a quantum correlation and a residual of quantum correlation as an indicator for the presence of an object in a noisy background or an extremely noisy background. In addition, the embodiment of the disclosure presents a normalized correlation measure to estimate the reflectivity of the object.
BACKGROUND
Generally, quantum correlations in the form of entanglement are a salient feature of quantum mechanics and is central to many quantum information processing protocols and quantum technology developments. However, these are generally known to be highly sensitive to environmental noise and can be easily destroyed thereby affecting advantages gained by nonclassical correlations. Quantum Illumination (QI) using quantum correlations between pair of entangled photons for object detection in a noisy environment is probably a known exception for object detection.
Usually, approaches that are in use for QI rely upon two entangled pair of beams in the form of signal photons and idler photons, which form a probe for object detection, wherein signal photons are directed to a region of space containing the object merged in background noise and the idler photon is stored locally until the signal reflects from the object. The enhancement of performance of QI over classical analog stands as a challenge and is made possible by using detection and joint measurement techniques which capture the nonclassical correlations between the stored idler photons and the reflected signal photons by isolating background noise. Typically, QI measurements focus on reducing uncertainty in unknown parameter estimation and false signal using quantum correlation. Thus, QI extends principles of target detection accuracy, ranging sensitivity, and degree of resilience towards preponderant noise from conventional lidar technology, radar technology to quantum metrology, and there is a need in the art for a better, efficient, and highly accurate method of detection of objects of very low reflectivity without any ambiguity of false detection especially in noisy background with very low signal to noise ratio by using quantum resources like entanglement and other forms of quantum correlations.

SUMMARY
Embodiments of the present disclosure relate to a method and system for determining a low reflectivity object and for quantifying reflectivity of an object, especially when the object located within a noisy background or an extremely noisy background. An embodiment of the present disclosure related to receiving simultaneously a signal photon along a signal path and an idler photon along an idler path at a receiver. In an embodiment, the signal photon and the idler photon are generated at simultaneously instant of time at source. In an embodiment, the signal photon and the idler photon being entangled in polarization degree of freedom at the source itself. In an embodiment, the signal photon configured to take at least one of a signal path or a reference path, and the idler photon configured to take an idler path.
In an embodiment the present disclosure conclusively denotes the presence of an object within a noisy background or an extremely noisy background, when a computed (which may be referred to as calculating or estimating) quantum correlation in the form of Clauser-Horne-Shimony-Holt (CHSH parameter) is greater than a first threshold value for quantum correlation. In an embodiment, the present disclosure conclusively denotes the presence of an object within a noisy background or an extremely noisy background, when a computed CHSH value is greater than a second threshold value for a residual of quantum correlation. In an embodiment, the CHSH value is computed using a coincidence measurement of the signal photon and the idler photon in different combination of polarization along the path of the signal photon and the path of the idler photon.

BRIEF DESCRIPTION OF THE DRAWINGS
The detailed description is described with reference to the accompanying figures. Features, aspects, and advantages of the subject matter of the present disclosure will be better understood with regard to the following description and the accompanying drawings. The figures are intended to be illustrative, not limiting, and are generally described in context of the embodiments, and it should be understood that it is not intended to limit the scope of the disclosure to these particular embodiments. In the figures, the same numbers may be used throughout the drawings to reference features and components. In order that the present disclosure may be readily understood and put into practical effect, reference will now be made to exemplary embodiments as illustrated with reference to the accompanying figures. The figures together with detailed description below, are incorporated in and form part of the specification, and serve to further illustrate the embodiments and explain various principles and advantages.
Figure 1 illustrates an exemplary set-up of the working of the system 100 in accordance with embodiments of the present disclosure.
Figure 2 illustrates an exemplary experimental set up 200 demonstrating generation of an entangled pair of photons forming a source in accordance with the embodiments of the present disclosure.
Figure 3 illustrates an exemplary experimental set up 300 demonstrating detection of an object using entangled photons in accordance with the embodiments of the present disclosure.
Figure 4 is an exemplary method illustrating generation of polarization entangled photons in accordance with an embodiment of the present disclosure.
Figure 5 is an exemplary method illustrating computing/estimating detecting the presence of an object in accordance with an embodiment of the present disclosure.
Figure 6 is an exemplary illustration of theoretically computed CHSH values in accordance with the embodiments of the present disclosure.
Figure 7 is an exemplary illustration of experimentally obtained maximum value of CHSH parameter in accordance with the embodiments of the present disclosure.
Figure 8 is an exemplary illustration of experimentally obtained maximum of CHSH values for different SNR for in accordance with the embodiments of the present disclosure.
Figure 9 is an exemplary plot illustrating of the effect of depolarizing noise, which shows the maximum of CHSH value Smax.
Throughout the drawings, identical reference numbers designate similar, but not necessarily identical elements. The figures as disclosed herein are not necessarily to scale, and the size of some parts may be exaggerated to more clearly illustrate the example shown. Moreover, the drawings are meant to only be provided as examples and/or implementations consistent with the description, and the description may not be limited to the examples and/or implementations provided in the drawings.

DETAILED DESCRIPTION
The following describes technical solutions in exemplary embodiments of the subject matter of the present disclosure with reference to the accompanying drawings. In this application as disclosed herein, "at least one" means one or more, and "a plurality of" means two or more. The term "and/or" describes an association relationship for describing associated objects and represents that three relationships may exist. For example, A and/or B may represent the following cases: Only A exists, both A and B exist, and only B exists, where A and B may be singular or plural. The character "/" usually indicates an "or" relationship between the associated objects. "At least one item (piece) of the following" or a similar expression thereof means any combination of the items, including any combination of singular items (piece) or plural items (pieces). For example, at least one item (piece) of a, b, or c may represent a, b, c, a and b, a and c, b and c, or a, b, and c, where a, b, and c each may be singular or plural.
It should be noted that in this application articles “a”, “an” and “the” are used to refer to one or to more than one (i.e., to at least one) of the grammatical object of the article. The terms “comprise” and “comprising” are used in the inclusive, open sense, meaning that additional elements may be included. It is not intended to be construed as “consists of only”. Throughout this specification defined above, unless the context requires otherwise the word “comprise”, and variations such as “comprises” and “comprising”, will be understood to imply the inclusion of a stated element or step or group of elements or steps but not the exclusion of any other element or step or group of elements or steps. The term “including” is used to mean “including but not limited to”. “Including” and “including but not limited to” are used interchangeably. In the structural formulae given herein and throughout the present disclosure, the following terms have been indicated meaning, unless specifically stated otherwise.
Unless otherwise defined, all terms used in the disclosure, including technical and scientific terms, have meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. By means of further guidance, term definitions are included for better understanding of the present disclosure. The term ‘about’ as used herein when referring to a measurable value such as a parameter, an amount, a temporal duration, and the like, is meant to encompass variations of ±10% or less, preferably ±5% or less, more preferably ±1% or less and still more preferably ±0.1% or less of and from the specified value, insofar such variations are appropriate to perform the present disclosure. It is to be understood that the value to which the modifier ‘about’ refers is itself also specifically, and preferably disclosed.
It should be noted that in this application, the term such as "example" or "for example" or “exemplary” is used to represent giving an example, an illustration, or descriptions. Any embodiment or design scheme described as an "example" or "for example" in this application should not be explained as being more preferable or having more advantages than another embodiment or design scheme. Exactly, use of the word such as "example" or "for example" is intended to present a related concept in only a specific manner.
It should be understood that in the embodiments of the present subject matter that "B corresponding to A" indicates that B is associated with A, and B can be determined based on A. However, it should be further understood that determining B based on A does not mean that B is determined based on only A. B may alternatively be determined based on A and/or other information.
In the embodiments of this application, "a plurality of" means two or more than two. Descriptions such as "first", "second" in the embodiments of this application are merely used for indicating and distinguishing between described objects, do not show a sequence, do not indicate a specific limitation on a quantity of devices in the embodiments of this application, and do not constitute any limitation on the embodiments of this application.
Embodiments of the present disclosure relate to a method and system for determining a low reflectivity object and quantifying reflectivity of an object, especially when the object located within a noisy background or an extremely noisy background. An embodiment includes simultaneously receiving a signal photon along a signal path and an idler photon along an idler path at a receiver. In an embodiment, the signal photon and the idler photon are generated at simultaneously instant of time at source. In an embodiment, the signal photon and the idler photon being entangled in polarization degree of freedom at the source itself. In an embodiment, the signal photon configured to take at least one of a signal path or a reference path, and the idler photon configured to take an idler path, wherein conclusively denotes the presence of an object within a noisy background or an extremely noisy background, when a computed quantum correlation parameter in the form of CSHS value is greater than a first threshold value for quantum correlation, and conclusively denotes the presence of an object within a noisy background or an extremely noisy background, when a computed CSHS value is greater than a second threshold value for a residual of quantum correlation. In an embodiment, the CHSH value is computed using a coincidence measurement of the signal photon and the idler photon in different combination of polarization along the path of the signal photon and the path of the idler photon. In an embodiment, when the presence of the object is confirmed, the normalized CHSH value which decreases with decrease in reflectivity of object is computed to estimate the reflectivity of object.
Exemplary embodiments of the present disclosure relate to a method and system for determining a low reflectivity object and for quantifying reflectivity of an object, especially when the object located within a noisy background or an extremely noisy background. In an exemplary case, the present disclosure related to receiving simultaneously a signal photon along a signal path and an idler photon along an idler path at a receiver (hereinafter also referred to as a measurement unit). In an exemplary case, the signal photon and the idler photon are generated at simultaneously instant of time at source. In an exemplary case, the signal photon and the idler photon being entangled in polarization degree of freedom at the source itself. In an exemplary case, the signal photon configured to take at least one of a signal path or a reference path, and the idler photon configured to take an idler path.
An exemplary case the present disclosure conclusively denotes the presence of an object within a noisy background or an extremely noisy background, when a computed CHSH value is greater than a first threshold value for quantum correlation. In an exemplary case the present disclosure conclusively denotes the presence of an object within a noisy background or an extremely noisy background, when a computed CSHS value is greater than a second threshold value for a residual of quantum correlation. In an exemplary case, the CHSH value is computed using a coincidence measurement of the signal photon and the idler photon in different combination of polarization along the path of the signal photon and the path of the idler photon.
In an exemplary case, the method and system additionally includes receiving the signal photon along a reference path at a receiver. In an exemplary case, the method and system conclusively denotes a reflectivity for the object when a computed normalized CHSH value corresponds to a pre-defined value mapped to the reflectivity, wherein the normalized CHSH value is computed using a coincidence measurement of the signal photon and the idler photon in different combination of polarization along the path of the signal photon, path of the reference photon and the path of the idler photon.
In an exemplary case, the method and system include a first pair of photons along the reference path and the idler path, and a second pair of photons along the signal path and the idler path. In the exemplary case, the first pair of photons and the second pair of photons being a subset of entangled pairs of photons. In the exemplary case, the entangled pair of photons being generated at a simultaneously instant of time T1.
In an exemplary case, computing (which may be referred to as calculating or estimating) the CHSH value (S) includes a coincidence measurement of the signal photons along the signal path and a idler photon along a idler path by changing the polarization combination of the photons. In an exemplary case, computing (which may be referred to as calculating or estimating) a normalized CHSH value (¯S) includes a coincidence measurement of the signal photons along the reference path and a idler along a idler path along with the coincidence measurement of signal photon along the signal path and the idler photon along a idler path. In an exemplary case, a combination of signal photon along signal path and idler photon along reference path and the idler photon along idler path are generated at simultaneously instant of time and are entangled in polarization degree of freedom.
In an exemplary case, the coincidence measurement is performed at a receiver based on a non-interferometry technique, and the coincidence measurement includes extracting information from the coincidence of the signal photon along signal path and idler photon along the idle path, and the signal photon along reference path and the idler photon along the idle path, in all combination of polarization degree of freedom of the signal photon and the idler photon. In an exemplary case, the non-interferometry technique implemented at the receiver includes isolating noise from the signal photon along signal path 138, the signal photon being received from the object.
In an exemplary case, the coincidence measurement for the pair of photons includes simultaneously detecting the signal photon travelling along the signal path and the idler photon travelling along the idle; and the signal photon travelling along reference path and idler photon travelling along the idle path. In an exemplary case, simultaneously detecting the signal photon along the signal path and along the reference path conclusively indicates the signal photon received at the receiver along signal path is a noise signal. In an exemplary case, simultaneously detecting the signal photon along the signal path and along the reference path without a simultaneous detection of idler photon conclusively indicates the signal photon along the signal path is a noise signal.
An exemplary case includes producing a pair of polarization-entangled photons at source 110, wherein the pair of polarization-entangled photons comprise the signal photon 112 and the idler photon 114 generated simultaneously. In the exemplary a polarization-entangled photons source produced by sourcing a pre-determined input wavelength F1 to a parametric down conversion unit. In the exemplary case, the polarization-entangled photon pairs of the signal photon and the idler photon have a same frequency/wavelength. In an exemplary case, the polarization-entangled pairs being the signal photon and the idler photon are generated at a simultaneously instant of time. In the exemplary case, the signal photon and the idler photon has a wavelength of F2, wherein the wavelength F2 = 2xF1. In an exemplary case, the entangled photons may have different frequencies. In An exemplary case, the polarization-entangled pairs always includes photons in a complementing polarization state, where if signal photon is in horizontal polarization, the idler photon will be in vertical polarization and vice versa thereby the signal photon and the idler photon being an entangled pair. It should be obvious to a person of ordinary skill in the art that various other techniques may be used to produce the polarization entangled photons all such sources and methods for generating polarization entangled photon pairs fall within the scope of the present disclosure.
An exemplary case includes transmitting the signal photon wherein the signal photon is distributed along the signal path and the reference path. In an exemplary case, signal photon along signal path is directed to detect the object and signal photon along the reference path is sent directly to the measuring unit. In an exemplary case, the computed CHSH value (S) between the signal photon along the signal path and the signal path confirms the presence of object. In an exemplary case, confirmation of object is when the first threshold value is 2 for the quantum correlation, and the second threshold value is between a range of 1.44 and 2 for the residual of quantum correlation.
In an exemplary case, the computed normalized CHSH value (¯S) using coincidence counts of photons in combination of polarization state of photons along the signal path and the idler path are normalized with coincidence counts of photons in reference path confirming a reflectivity of the object, for a pre-defined correlation value mapped to reflectivity of object. In an exemplary case, an optimized coincidence count of the idler photon and the signal photon may be obtained by varying the path length of the idler photon to match the total path length of the signal photon, from source to object and object to measurement unit, to range the position and distance of the object.
In an exemplary case, for any entangled state of photons in signal path, reference path and idler path the present disclosure conclusively indicates the presence of the object if the computed CHSH (S) for the first threshold is 2 for the quantum correlation, and for the second threshold is between 1.44 and 2 for the residual of quantum correlation. In an exemplary case, for any entangled pair of photons in the signal path, the reference path and idler path conclusively indicate reflectivity of the object corresponding to a decrease in the normalized CHSH value, (¯S) with decrease in reflectivity.
Reference is now made to Figure 1, which illustrates an exemplary set-up of the working of the system 100 in accordance with embodiments of the present disclosure. Embodiments of the present disclosure are related to a method and a system to determine a low reflectivity object 125 and further to quantifying reflectivity of object 125. In an exemplary embodiment, system 100 include source 110 and a receiver 130, and further includes an environment 120. In an embodiment, a pair of polarization-entangled photons is produced at source 110, wherein the pair of polarization-entangled photons comprise the signal photon 112 and the idler photon 114 generated simultaneously. It should be obvious to a person of ordinary skill in the art that various other techniques may be used to produce the polarization entangled photons all such sources and methods for generating polarization entangled photon pairs fall within the scope of the present disclosure. In the exemplary case source 110 configured to generate a polarization-entangled photons by receiving photons at a pre-determined input frequency F1. In the exemplary case, source 110 parametrically down convert the photons to generate a pair of polarization-entangled photons, wherein the pair of polarization-entangled photon comprising a signal photon 112 and an idler photon 114, the signal photon 112 and the idler photon 114 have a same frequency.
In an exemplary case, environment 120 includes an object 125 located within environment 120, wherein environment 120 comprises a noisy background. In the exemplary case, system 100 further includes receiver 130. Reciiver 130 is configured to receive a signal photon 112 along a signal path 138 and/or a reference path 134 and an idler photon 114 along an idler path 136. In the exemplary case, the signal photon 112 along the signal path 138 and/or the reference path 134 and the idler photon 114 from the idler path 138 arrive simultaneously at a receiver 130. In the exemplary case, receiver 130 is configured to compute a CHSH value (S). In the exemplary case, computing (which may be referred to as calculating or estimating) CHSH value includes performing a coincidence measurement of the signal photon 112 and the idler photon 114 in different combination of polarization of photons of the signal photon 112 along the signal path 138 and the idler photon 114 along the idler path 136. In the exemplary case, the CHSH value conclusively denotes presence of the object 125 within the noisy background 120 if the computed CHSH value (S) is greater than a first threshold value, or the computed CHSH value (S) is greater than a second threshold and less than the first threshold indicating a residual of quantum correlation. In the exemplary case, the first threshold has a value of 2 and the second threshold has a value 1.44.
In an embodiment, quantifying reflectivity of the object 125 in the noisy background 120 is determined at the receiver 130. In the exemplary case, receiver 130 is configured to compute a normalized CHSH value (¯S) by measuring a coincidence of the signal photon 112 and the idler photon 114 in different combination of polarization of the signal photons along the signal path 138, the signal photons along the reference path 134 and the idler photon along the idler path 136. In the exemplary case, the normalized CHSH values (¯S) are mapped to pre-defined set of values corresponding to reflectivity of an object.
In the exemplary case, the signal photon 112 is received along the reference path 134 and the idler photon 114 is received along the idler path 136 at the receiver 130, and the signal photon 112 is received along the signal path 138 and the idler photon 114 is received along the idler path 136 at the receiver 130, wherein the signal photon 112 and the idler photon 114 being an entangled pair of photons being simultaneously generated at the source 110 at an instant of time T1.
In the exemplary embodiment, the coincidence measurement is performed at a receiver 130 based on a non-interferometry. In the exemplary embodiment the coincidence measurement includes extracting information from a coincidence of the signal photon 112 along signal path 138 and idler photon 114 along the idler path 136, and the signal photon 112 along reference path 134 and the idler photon 114 along the idle path 136 in all combinations of polarization degree of freedom of the signal photon 112 and the idler photon 114. I the exemplary case, the non-interferometry implemented at the receiver 130 comprises isolating the noise 120 from the signal photon 112 along signal path 138 received from the object 125. It should be obvious to a person skilled in the art that other techniques may be used to perform coincidence measurements and all such techniques fall within the scope of the present disclosure.
In the exemplary case, receiver 130 of system 100 configured to simultaneously detect the signal photon 112 along signal path 138 and the signal photon 112 along the reference path 134 and/or the signal photon 112 along the signal path 138 and the signal photon 112 along the reference path 134 without a simultaneous detection of idler photon 114. In the exemplary case, this allows to conclusively indicate the signal photon received at the receiver 130 along signal path 138 is a noise signal and no object has been detected.
In the exemplary case, source 110 of system 100 configured to produce polarization-entangled photons. In the exemplary case, source 110 sources a pre-determined input wavelength F1 to a parametric down conversion unit, wherein a pair of polarization-entangled photons 112, 114 are generated and the polarization-entangled photons 112, 114 have a same frequency. In the exemplary case, the polarization-entangled pairs being the signal photon 112 and idler photon 114 , which are generated at a simultaneously instant of time at the source 110, wherein the signal photon 112 and the idler photon 114 has a wavelength of F2, wherein the wavelength F2 = 2xF1. In the exemplary case, the signal photon 112 and the idler photon 114 include complementing polarization state. In the exemplary case, if signal photon 112 is in a horizontal polarization state the idler photon 114 is in a vertical polarization state and if signal photon 112 is in a vertical polarization state the idler photon 114 is in a horizontal polarization state thereby making the photons as an entangled pair. It should also be obvious to a person of ordinary skill in the art that the polarization entangled photons may have different frequencies and all such variation fall within the scope of the present disclosure.
In the exemplary case, the signal photon 112 along signal path 132 is directed to detect the object 125 and signal photon 112 along the reference path 134 is directed to the receiver130. In the exemplary case, any entangled photons in the signal path 138, the reference path 134 and the idler path 136 conclusively indicating presence of object based on the CHSH value (S) and reflectivity of the object corresponding to a decrease in normalized CHSH value (¯S) with decrease in object reflectivity.
Source 110 is preferably a monochromatic light source such as a laser source configured to emit radiation at a pre-defined wavelength. Source 112 emits first photon 112 and second photon 114, where first photon 112 and second photon 114 are entangled at source in polarization and path degree of freedom. Photons from an input source need to be down converted to form an pair of photons at source 110. In case of down-conversion Spontaneous parametric down-conversion (also known as SPDC, parametric fluorescence or parametric scattering) is a nonlinear instant optical process that converts one photon of higher energy (namely, a pump photon), into a pair of photons (namely, a signal photon, and an idler photon) of lower energy. In accordance with the present disclosure, source 110 is configured to produce a pair of photons, first photon 112 and second photon 114, wherein the photons are entangled in degrees of polarization.
First photon 112 (hereinafter also referred to as signal photon) may be considered as a signal photon and second photon 114 (hereinafter also referred to as an idler photon) may be considered as a idler photon. Signal photon 112 may be configured to take either one of signal path 132 or reference path 134. Idler photon may be configured to take the idler path 136. Signal photon Along the reference path 134 may be received at detection unit 130 along with idler photon 136. When both signal photon 112 is received along reference path 134 and idler photon 114 received along idler path 136, at a simultaneously instant at detection unit 130, the result may be conclusive that the photon(s) received via signal path 138 may be a noise signal. A CHSH value (S) 135 computed at the detector unit 130 is used to determine the presence of an object or whether the signal photon received is particularly related to noise received at detector 130 (detector and detector unit are being interchangeably used in the present disclosure).
Signal photon 112 generated at source 110 along with idler photon 114, may take an alternate path. Signal photon 112 may take signal path 132 and be directed to detect object 125, which may be placed in a noisy environment 150, where noisy environment in a specific embodiment may be a cloudy environment. It should therefore be obvious to a person skilled in the art that the object may be embedded or located within various other noisy environments and any noisy environment falls within the scope of the present disclosure. Signal photon 112 taking signal path 132 and directed to detect object 125, and on detection of object signal photon 112 will be reflected from object 125 along signal path 138. Signal photon taking signal path 132 and signal path 136 with idler photon taking idler path 136 at detector 130, may be used to compute the CHSH value (S) and conclusive indicating the presence of object 125 in noisy background 120 based on the computed CSHS value (S), which has been previously disclosed.
In the exemplary case, the entangled photon pairs may be represented by the equation

The CHSH values may be computed using the equation.

Experimentally, E(a, ß) may be computed using coincidence detection for various combination of angles,

where N(a, ß) is the coincidence count at the rotation angle of the polarization - a, ß.
Further, the normalized CHSH value may be computed using the correlation value E(a, ß) concerning to CHSH value changes to

where Ref value is from reference and idler path coincidence counts and Act is from signal path and idler path coincidence.
In an exemplary case, entangled light sources may be used for illuminating objects which offers advantages over conventional illumination methods by enhancing the detection sensitivity of a reflecting object. In the exemplary case, quantum advantage lies in practically leverage quantum correlations to isolate background noise 120 and detect the low reflectivity object 125. Embodiments of the present disclosure experimentally demonstrated the advantages of using polarization-entangled photon pairs for quantum illumination and show that the quantum correlation measure using CHSH value (S) computed is robust against background noise and any losses due to background noise. In the exemplary case, residual of quantum correlations is used identifying the object of reflectivity, where reflectivity ? as low as 0.05 and when signal-to-noise ratio is as low as 0.003 for reflectivity ? = 0.7, which surpasses earlier demonstrated results. In the exemplary case, robustness of correlation measure with photon attenuation in atmospheric condition may be analyzed to show the practical feasibility of the real time application.
In an exemplary case, quantum information (QI) is computed experimentally, where a QI scheme using polarization-entangled photons, which uses Bell’s inequality measurement, CHSH value (S)_as the quantum correlation measure may be demonstrated. In the exemplary case, the CHSH value (S) is used for identifying the presence of object and normalized CHSH value (S), where S is used for predicting the reflectivity of the object after detecting the presence of the object. In the exemplary case, the CHSH value (S) helps in identifying the range of CHSH value where quantum correlations may be absent but may be marked as a residual of quantum correlation obtained due to the entanglement in the probe state. In the exemplary case, a value of S > 2 in the scheme indicates the quantum correlation, and a value of v2 = S = 2 signifies classical residual to the quantum correlations, which may be used for conclusively confirming the presence of object in any noisy background or noisy environment. In the exemplary case, these bounds are fixed by using the maximum S value that can be achieved with the same polarizing angles for a separable state, i.e., S = v2. In the exemplary case, in accordance with the embodiment of the present disclosure, experimental results show quantum correlation, S > 2 up to object reflectivity ? = 0.1 and residual of quantum correlation, 2 = S = 2 for ? = 0.05. In the exemplary case, even in presence of background noise with signal-to-noise ratio (SNR) of 0.03 a value of S > v2 when reflectivity is of the order of ? = 0.7. In the exemplary case, in comparison to another scheme, signal path 132 and idler path 136 may be divided into four channels each. In the exemplary case, eight (8) detectors may be used to perform or measurements in real time, and range of the object can be estimated by calculating the delay in arrival time with a high degree of accuracy.
In the current exemplary QI scheme as disclosed herein, the entangled state comprises signal photon 112 which will be directed towards the target 120 (object 120 within the noisy background 120) idler photon 114 which will be directly sent to the detector 130 (also referred to as receiver). A correlation measurement, CHSH value (S), between the returning signal photon 112 when object 125 is present and idler photon 114 at the receiver 130 isolates the noise and confirm the presence of the object 125. In the exemplary case, polarization-entangled photons are used, where signal photon 112 is split into two beams, where one beam is directed to detect object 125 and the other beam sent to the detector 130. Idler photon 114 serves as a reference and a final measurement is based on the joint detection and CSHS value of the photon pair.
Reference is now made to Figure 2, which illustrates an exemplary experimental set up 200 demonstrating generation of an entangled pair of photons in accordance with the embodiments of the present disclosure. In the exemplary experimental setup illustrated, various modification could be made to the setup to achieve the same results following the principles of the present disclosure, and it should be obvious to a person skilled in the art that all such modification fall within the scope of the present disclosure.
In the exemplary experimental setup, polarization-entangled photons at 810 nm are generated from an SPDC process using a BBO nonlinear crystal. The crystal is type-II phase matched with a thickness of 3 mm. The schematic of the experimental setup for generating entangled photons pairs is illustrated in Figure 2. BBO crystal was pumped using a continuous wave diode laser at 405 nm with a spectral line width of 0.6 nm and a pump power of 10 mW. A half-waveplate at 405 nm is used to set the pump polarization perpendicular to the optical axis of the BBO crystal. An achromatic lens of 25 mm was used to tightly focus the pump laser into the centre of the crystal. The spatial distribution of the horizontal and vertically polarized SPDC photon pairs is captured using an EMCCD camera. A typical image of the generated SPDC photon pairs is shown in the inset. The two intersection regions in the image are the polarization-entangled photons.
A wedge-mirror was used to direct the entangled photons into two arms for ease of coupling to a single-mode optical fiber. To compensate for the transverse and longitudinal walk-off of horizontally polarized photons to the vertically polarized photons, a half-waveplate at an angle of p/4 was employed and BBO compensation crystal of 1.5 mm thickness in both arms. The residual pump photons are filtered using an interference filter (810 ± 10 nm) before entering to the single-mode fiber. The single-mode fibers are preloaded with a fiber polarization controller to correct the random polarization on the photons induced by the fiber.
To quantify the polarization entanglement the fiber coupled entangled photons are sent to fiber-coupled single photon counting modules (SPCM) after passing through a polarizer. The output of the SPCMs is fed to a time-correlated single photon counter. Initially, the coincidence visibility of the photons in the horizontal (H)/vertical (V) and Anti-diagonal (A)/diagonal (D) polarization basis are maximized. The visibility in the H/V and A/D basis is maximized by turning the coupling to optical fiber and tilting the BBO compensator crystals. The measured visibility of the polarization entangled source in the H/V basis is around 97% while in the A/D basis, it is around 94%. The calculated CHSH value for the source is 2.72 ± 0.05.
Reference is now made to Figure 3, which illustrates an exemplary experimental set up 300 demonstrating detection of an object using entangled photons in accordance with the embodiments of the present disclosure. The setup 300 consist of three modules, source module 310 to generate the entangled photon source, illumination unit 320, which consists of the object placed within a noisy background and measurement unit 330, consisting of detectors to perform measurements. Each of the functioning of these unit will be explained further below. As illustrated a Laser is provided as input to source unit 310 (described in Figure 2) to generate an entangled pair of photons. The entangled pair of photons generated at the source 310, where one photon from the entangled pair is considered to be the signal photon and the second photon from the entangled pair is the idler photon. As disclosed with respect to Figure 1, the signal photon may take the signal path and/or the reference path, and the idler photon takes the idler path,
The illumination unit 320 as illustrated in Figure 3 includes an object that is kept in a noisy background, wherein for the experimental setup a strong white light source is used to create a noisy background wherein the object is embedded. The signal photon taking the path to be object may be reflected from the object and collected at measurement unit 330, wherein the signal photon travelling the path through the object, arriving at measurement unit 330 (also referred to as a receiver in the present disclosure) includes the signal photon with noise data. Alternatively, if the signal photon takes the reference path, then the photons collected at measurement unit (receiver) 330 via the signal photon path implies that the photons are purely due to noise and not that reflected from an object in the noisy environment/background. The path length of the signal photons, the reference photon and the idler photon may be adjusted along the fiber used in the experimental setup to demonstrate enablement of the present disclosure. From the photons collected at measurement unit 330, measurements may be made, and the presence of an object may be predicted with a high level of accuracy, from the reference values and the object information values.
Exemplary Figure 3 illustrates the schematic of the experimental setup used 300 for quantum illumination using polarization entangled photon pairs, signal, and idler. The generated fibre-coupled signal and idler photon counts were about 7000 c/s. The entangled photons in the signal path and idler path were passed through a 50:50 beam splitter. The reflected photons from both the signal path and idler path were sent directly to measurement unit 330. The transmitted signal photons were sent towards the object in illumination unit 320 whereas the transmitted idler photons were sent directly to measurement unit 330. The object used in illumination unit 320 was a beam splitter having varying/different reflectivity ?. In the exemplary case, the reflectivity ? was varied in the range from 1 to 0.05. Finally, the CHSH value was computed between the photons that were reflected from the object and the transmitted arm of the idler. Through this procedure, the property of the object’s reflectivity was analysed in real-time with a high level of accuracy. In the exemplary case, referencing the signal photons and idler photons may be done to compute the quantum correlations for two types of scenarios.
In the exemplary case, while demonstrating the effects of noise and depolarizing effects, primarily the direct measurement of the CHSH value were relied upon from the object arm and one of the idler arms. To investigate the impact of noise, a fibre-coupled white halogen light source was connected to one of the arms of the object beam splitter. In an exemplary case, this may be a tuneable thermal light source, allowing adjustments to be made to attain various SNR values, where the SNR was varied from 1 to 2×10-3.
In the exemplary experimental case, realizing depolarizing noise is challenging, with an approach to address this including using two calcite crystals and quarter-waveplate in the signal arm, where the quarter-waveplates’ rotation angle serve as depolarizing values, or another approach is to introduce a combination of a quarter-wave plate, a half waveplate, and another quarter-waveplate(Q-H-Q) in the signal arm to achieve the depolarizing noise. In the exemplary case, the quarter-waveplates are fixed at angles of -p/4 and p/4, while the half-waveplate is rotated to serve as the depolarizing value. Then the quantum state may be represented by the equation
,
where, the 2nd term in the equation above reflects the depolarizing factor. As the angle ? increases the depolarizing effect increases, and it may be maximum when HWP angle is p/4 because in half-waveplate, 2? dependence is an inherent factor, and in the expression, 4? term were obtained, so the depolarizing value p becomes 1 when the half-waveplate angle becomes p/4.
In the exemplary experimental case, in accordance with the present disclosure, it was demonstrated that a QI scheme using polarization-entangled photons, which uses Bell’s inequality measurement, CHSH value as the quantum correlation may be measured. In the experimental case, the CHSH value, S is used for identifying the presence of object and normalised CHSH value, ¯S, is used for predicting the reflectivity of the object after detecting the presence of the object. In the exemplary experimental case, unlike other quantum correlation measures used for QI, the CHSH value assists in identifying the range of value of S where quantum correlations are absent but can be marked as a residual of quantum correlation obtained due to the entanglement in the probe state for the photons. In the exemplary experimental case, the value of S > 2 in the scheme indicates the quantum correlation, and v2 = S = 2 signifies classical residual to the quantum correlations which can be used for confirming the presence of object. In the exemplary experimental case, these bounds are fixed by using the maximum S value that can be achieved with the same polarizing angles for a separable state, that is S = v2. In the exemplary experimental case, results show a quantum correlation, i.e., S > 2 up to object reflectivity ? = 0.1 and residual of quantum correlation, v2 = S = 2 for object reflectivity ? = 0.05. In the exemplary experimental case, even in presence of background noise with signal-to-noise ratio (SNR) of the order of 0.03, a quantum correlation value S > v2 was obtained when the object reflectivity ? = 0.7. In the exemplary experimental case, comparing with another scheme, if the signal path and idler path are divided into four channels each, then use of 8 detectors allows measurements to be performed in real time and range of the object may be estimated by computing (which may be referred to as calculating or estimating) the delay in arrival time with respect to the photons in the measurement unit 330.
In the exemplary experimental case, apart from considering reflectivity of the object and SNR, another crucial aspect of object detection using a quantum probe includes the estimation and effect on purity of quantum probes due to atmospheric attenuation. In the exemplary experimental case, considering a NOON state as a probe, where the atmosphere affects the interference pattern, and the standard deviation of an operator dA may be considered as a measure to obtain a bound. In the exemplary experimental case, modeled single photon attenuation due to the atmosphere and how the CHSH value behaves with distance are measured. In the exemplary experimental case, these type of attenuation effects and accordingly estimate that up to 25 kms distance the value of S > v2 may be obtained, which is a significant advantage over know techniques, and the presence of an object may be easily identified by use of this technique. In the exemplary experimental case, this distance covers the lateral distance of atmosphere where attenuation of the photons occurs.
Reference is now made to Figure 4, which is an exemplary method illustrating generation of polarization entangled photons in accordance with an embodiment of the present disclosure. At step 410 source photons from a laser are provided to a polarization-entangled photon generating unit as shown in Figure 2. The photon provided as input are at a frequency/wavelength of F1 to generate the polarization entangled photon pair. At step 420, the photon at frequency F1 is down converted to polarization entangled photon pair having a frequency F2, where F2 = F1 *2. One of the photons from the pair of photons is the signal photon 112 and the other photon from the pair is the idler photon 114, which has been described with respect to Figure 1 and Figure 2. At step 430, the signal photon 112 is transmitted along the signal path 132 or along the reference path 134 and the idler photon is transmitted along the idler path 136, which has been previously described with respect to Figure 1, Figure 2 and Figure 3.
Reference is now made to Figure 5, which is an exemplary method illustrating computing (estimating) detecting the presence of an object in accordance with an embodiment of the present disclosure. At step 510, the signal photon travelling along the signal path 138 and/or along the reference path 134 and the idler photon travelling along the idler path 136 is received at receiver 130. At step 520, a CHSH value (S) and a normalized CHSH value (¯S) may be computed, which has been described in details with respect to Figure 1, Figure 2 and Figure 3, by performing a coincidence measurement at the receiver 130 and the presence/absence of an object can be determined. At step 530, based on the CHSH value and the presence of an object in the noisy background may be determined, either in the quantum correlation region or residual quantum correlation region. Based on the normalized CHSH value (¯S) allows to quantity the object reflectivity for extremely low reflectivity object.
Reference is now made to Figure 6, which illustrates an exemplary theoretically computed CHSH values using different, entangled, pure separable, and maximally mixed state as probes for two different theoretical models, which are presented as a function of object reflectivity (?) ranging from 0.05 to 1. Depending on the maximum value n using each probe state, the quantum bound, classical bound (CB) and the residual quantum bound (RQB) may be obtained or computed. The region within the bounds is shown in different shades of grey scale. For all the probe states the standard CHSH value (Smax) shows different values that set the bounds but remains constant for all non-zero object reflectivity ?. Except for the case of maximally mixed state, normalized CHSH value (¯Smax) decreases with decrease in object reflectivity ?. In the case of maximally mixed state for both scenarios, CHSH-value remain 0.
Reference is now made to Figure 7, which illustrates an exemplary experimentally obtained maximum value of CHSH value, Smax for an object of different reflectivity (?). As illustrated in the Figures, the cross points show the experimentally obtained data for various object reflectivity, and at an object reflectivity ? ˜ 0.05 the CHSH-value goes below 2 but lies in the residual of quantum region. Decrease in the value of CHSH value (S) indicates the limit of reflected photons getting close to the dark counts of the detectors. The inset figure shows how the normalized CHSH-value (¯Smax) changes with different object reflectivity ?, where the curve along the cross marked points represent the theoretical computed values.
In the plot illustrated is experimentally obtained CHSH value, Smax when objects of different object reflectivity ? were illuminated using polarization-entangled photons. The upper shaded region in the plot shows the bound on the value of Smax to be quantum. The data points with error bars show the value of Smax for different object reflectivity. It should be noted that the Smax remains the same for object reflectivity ? up to 0.3. However, when the object reflectivity is 0.2, the reflected signal from the object is 700 c/s and when the object reflectivity is 0.05, the reflected signal from the object further decreases to 175 c/s, which is comparable to the dark count of the detector. As a result of the random effect of dark counts, the S-value dropped below 2 for object reflectivity ? = 0.05, but it remains in the residual quantum region. The inset in the Figure shows the effect of object reflectivity on ¯Smax. The data points with error bar shows the experimental data and the theoretical model (solid line) is shown for comparison, and hence experimental results confirm that using Smax the presence of an object may be confirmed with a high degree of accuracy and by using ¯Smax, the object reflectivity ? can be easily estimated.
Reference is now made to Figure 8, which illustrates an exemplary experimentally obtained data of the effect of back-ground noise. In the exemplary experimental data maximum of CHSH value for different SNR, wherein. at the x-axis is log of SNR. The CHSH value remains within the quantum and residual of quantum bound for SNR value as low as 0.002 for object reflectivity ? = 0.9 (top line, indicated with a dashed line) and for SNR value of 0.03 for object reflectivity ? = 0.7 (bottom line, indicated as a dotted line). Here the CHSH-value drops due to false coincidence counts.
In the plot the experimentally obtained maximum of CHSH value when background thermal noise was introduced. The square data points and star data points shown are for object reflectivity, ? of 0.9 and 0.7, respectively. By keeping the signal counts fixed, the background thermal noise was increased. The SNR was varied from 1 to 2 × 10-3. The SNR is plotted in log10 scale, where with increasing the thermal background noise the Smax value remains almost the same for SNR above 0.3 ( -1.522 ).
For object reflectivity ? = 0.9 further increasing the noise level results in slow decrease in Smax from 2.598±0.008 to 2.217±0.019 when SNR reaches 0.005 (-2.30). Further increasing the noise level, the Smax drops below to 2 but still inside the residual of quantum bound, Smax = 1.507±0.012 at SNR of 0.002 (-2.69). For object reflectivity ? = 0.7, a similar trend is seen. However, at SNR 0.002 (-2.69), the Smax value becomes 1.199±0.007. These results indicate the decrease is S value is seen only when the reflected photon detection counts reaches the limits of detector dark counts.
Reference is now made to Figure 9, which illustrates an exemplary plot of the effect of depolarizing noise, which shows the maximum of CHSH value, Smax. The square data points and star data points show the experimentally obtained Smax for object reflectivity ? of 0.9 and 0.7, with a change in depolarization value. The solid line shows the theoretical model curve. The plot shows the maximum value of Smax as a function of depolarization value for object reflectivity, ? 0.9 and 0.7. The depolarization value was estimated from the polarization visibility of entangled photons by varying the half-waveplate in the Q-H-Q as mentioned in the second term of Equation above. The data points (square) and data points (asterisk) show the Smax for ? = 0.9 and ? = 0.7. The solid line shows the theoretical model using Equation above. The observed data matches with the theoretical mode.
In the exemplary experiment it was demonstrated that the QI protocol using polarization-entangled photon pairs based on the CHSH value as a measure of quantum correlation. The experimental results were aligned with the theoretical predictions. Quantum correlation was computed across various object reflectivity, assessed the impact of background noise on quantum correlation, and explored classical correlation. However, residual of quantum phenomena contributes to extending the limits. Additionally, the effect of depolarizing noise in the signal arm was also considered and its influence on the CHSH value. Finally, a photon attenuation scheme was used to determine the distance over which our scheme maintains quantum correlations, and the CHSH value were quantified which captures only classical correlation but can be called and used as the residual of quantum correlation for illumination purpose. Explicit use of residual of quantum correlation identify the presence of an object of low reflectivity even when SNR is as low as 0.003.
Although the present disclosure has been described with reference to several preferred embodiments, it should be understood that the present disclosure is not limited to the preferred embodiments disclosed here. Embodiments of the present disclosure are intended to cover various modifications and equivalent arrangements within the spirit and scope of the appended claims. Although the foregoing disclosure has been described in some detail for purposes of clarity of understanding, it will be apparent that certain changes and modifications may be practised within the scope of the appended claims. Examples of the present disclosure have been described in language specific to structural features and/or methods. It should be noted that there are many alternative ways of implementing both the process and apparatus of the present invention. Accordingly, embodiments of the present disclosure are to be considered illustrative and not restrictive, and the invention is not to be limited to the details given herein but may be modified within the scope and equivalents of the appended claims. It should be understood that the appended claims are not necessarily limited to the specific features or methods described. Rather, the specific features and methods are disclosed and explained as examples of the present disclosure
, C , C , Claims:We Claim:

A method for determining a low reflectivity object 125 and quantifying reflectivity of the object 125, the object 125 located within a noisy background 120, the method comprising:
receiving a signal photon 112 along a signal path 138 and/or a reference path 134 and an idler photon 114 along an idler path 136 at a receiver 130, wherein the signal photon 112 along the signal path 138 and/or the reference path 134 and the idler photon 114 from the idler path 138 arrive simultaneously at a receiver 130; and
estimating a quantum correlation parameter in form of Clauser-Horne-Shimony-Holt (CHSH) value (S) at the receiver 130, wherein estimating the CHSH value comprises:
a coincidence measurement of the signal photon 112 and the idler photon 114 in different combination of polarization of photons of the signal photon 112 along the signal path 138 and the idler photon 114 along the idler path 136; and
conclusively denoting presence of the object 125 within the noisy background 120 if
the computed CHSH value (S) is greater than a first threshold value;
the computed CHSH value (S) is greater than a second threshold and less than the first threshold, indicating a residual of quantum correlation.

The method as claimed in claim 1, wherein the first threshold value is 2 and the second threshold value is 1.44.

The method as claimed in claim 1, the method comprising:
quantifying reflectivity of the object 125 in the noisy background 120 by
estimating a normalized CHSH value (¯S) by
performing a coincidence measurement of the signal photon 112 and the idler photon 114 in different combination of polarization of the signal photons along the signal path 138, the signal photons along the reference path 134 and the idler photon along the idler path 136.

The method as claimed in claim 2, wherein the normalized CHSH value (¯S) are mapped to pre-defined set of values corresponding to reflectivity of an object.

The method as claimed in claim 1, the method comprising:
receiving the signal photon 112 along the reference path 134 and the idler photon 114 idler path 136, and
receiving the signal photon 112 along the signal path 138 and the idler photon 114 along the idler path 136;
wherein the signal photon 112 and the idler photon 114 being an entangled pair of photons simultaneously generated at a source 110 at a same instant of time T1.

The method as claimed in claim 1, wherein the coincidence measurement is performed at a receiver 130 based on a non-interferometry, and the coincidence measurement comprises:
extracting information from coincidence of
the signal photon 112 along signal path 138 and idler photon 114 along the idler path 136, and
the signal photon 112 along reference path 134 and the idler photon 114 along the idle path136
in all combinations of polarization degree of freedom of the signal photon 112 and the idler photon 114.
The method as claimed in claim 5, wherein the non-interferometry implemented at the receiver 130 comprises:
isolating the noise 120 from the signal photon 112 along signal path 138 received from the object 125.

The method as claimed in 1, the method comprising:
detecting simultaneously
the signal photon 112 along signal path 138 and the signal photon 112 along the reference path 134; and/or
the signal photon 112 along the signal path 138 and the signal photon 112 along the reference path 134 without a simultaneous detection of idler photon 114 along the idler path 136
and conclusively indicating the signal photon received at the receiver 130 along signal path 138 is a noise signal.

The method as claimed in claim 1, the method comprising:
producing a pair of polarization-entangled photons at the source 110, wherein the pair of polarization-entangled photons comprise the signal photon 112 and the idler photon 114 generated simultaneously.

The method as claimed in claim 8, wherein the signal photon 112 and the idler photon 114 comprises complementing polarization state, the complementing polarization states being:
if signal photon 112 is in a horizontal polarization state the idler photon 114 is in a vertical polarization state and
if signal photon 112 is in a vertical polarization state the idler photon 114 is in a horizontal polarization state
thereby making the photons as an entangled pair.

The method as claimed in claim 9, wherein the signal photon 112 along signal path 132 is directed to detect the object 125 and signal photon 112 along the reference path 134 is directed to the receiver 130.

The method as claimed in claim 2, wherein any entangled photons in the signal path 138, the reference path 134 and the idler path 136 conclusively indicating presence of object based on the CHSH value (S) and reflectivity of the object corresponding to a decrease in normalized CHSH value (¯S) with decrease in object reflectivity.

A system 100 to determine a low reflectivity object 125 and quantifying reflectivity of the object 125, the system comprising a source 110, an environment 120 and a receiver 130,
the source 110 configured to generate:
a polarization-entangled photons by receiving photons at a pre-determined input frequency F1;
parametrically down convert the photons to generate a pair of polarization-entangled photons, wherein the pair of polarization-entangled photon comprising a signal photon 112 and an idler photon 114, the signal photon 112 and the idler photon 114 have a same frequency;
the environment 120 comprises:
an object 125 located within the environment 120, wherein the environment 120 comprises a noisy background;
the receiver 130 configured to
receive a signal photon 112 along a signal path 138 and/or a reference path 134 and an idler photon 114 along an idler path 136, wherein the signal photon 112 along the signal path 138 and/or the reference path 134 and the idler photon 114 from the idler path 138 arrive simultaneously at a receiver 130; and
estimate a CHSH value (S) at the receiver 130, wherein estimating CHSH value comprises:
performing a coincidence measurement of the signal photon 112 and the idler photon 114 in different combination of polarization of photons of the signal photon 112 along the signal path 138 and the idler photon 114 along the idler path 136; and
conclusively denoting presence of the object 125 within the noisy background 120 if
the estimated CHSH value (S) is greater than a first threshold value; and
the estimated CHSH value (S) is greater than a second threshold and less than the first threshold indicating a residual of quantum correlation.

The system as claimed in claim 13, wherein the first threshold is 2 and the second threshold is 1.44.

The system as claimed in claim 13, wherein quantifying reflectivity of the object 125 in the noisy background 120 is determined by
estimating a normalized CHSH value (¯S) by
a coincidence measurement of the signal photon 112 and the idler photon 114 in different combination of polarization of the signal photons along the signal path 138, the signal photons along the reference path 134 and the idler photon along the idler path 136.

The system as claimed in claim 14, wherein the normalized CHSH values (¯S) are mapped to pre-defined set of values corresponding to reflectivity of an object.

The system as claimed in claim 13, wherein
the signal photon 112 is received along the reference path 134 and the idler photon 114 is received along the idler path 136 at the receiver 130, and
the signal photon 112 is received along the signal path 138 and the idler photon 114 is received along the idler path 136 at the receiver 130;
wherein the signal photon 112 and the idler photon 114 being an entangled pair of photons being simultaneously generated at the source 110 at an instant of time T1.

The system as claimed in claim 13, wherein the coincidence measurement is performed at a receiver 130 based on a non-interferometry, and the coincidence measurement comprises:
extracting information from a coincidence of
the signal photon 112 along signal path 138 and idler photon 114 along the idler path 136, and
the signal photon 112 along reference path 134 and the idler photon 114 along the idle path136
in all combinations of polarization degree of freedom of the signal photon 112 and the idler photon 114.

The method as claimed in claim 18, wherein the non-interferometry implemented at the receiver 130 comprises isolating the noise 120 from the signal photon 112 along signal path 138 received from the object 125.

The system as claimed in 13, the system configured to simultaneously detect
the signal photon 112 along signal path 138 and the signal photon 112 along the reference path 134 ; and/or
the signal photon 112 along the signal path 138 and the signal photon 112 along the reference path 134 without a simultaneous detection of idler photon 114,
conclusively indicating the signal photon received at the receiver 130 along signal path 138 is a noise signal.

The system as claimed in claim 13, the system configured to produce a pair of polarization-entangled photons at the source 110, wherein the pair of polarization-entangled photons comprise the signal photon 112 and the idler photon 114 generated simultaneously.

The system as claimed in claim 21, wherein the signal photon 112 and the idler photon 114 comprises complementing polarization state, the complementing polarization states being:
if signal photon 112 is in a horizontal polarization state the idler photon 114 is in a vertical polarization state and
if signal photon 112 is in a vertical polarization state the idler photon 114 is in a horizontal polarization state
thereby making the photons as an entangled pair.

The system as claimed in claim 22, wherein the signal photon 112 along signal path 132 is directed to detect the object 125 and signal photon 112 along the reference path 134 is directed to the receiver130.

The system as claimed in claim 14, wherein any entangled photons in the signal path 138, the reference path 134 and the idler path 136 conclusively indicating presence of object based on the CHSH value (S) and reflectivity of the object corresponding to a decrease in normalized CHSH value (¯S) with decrease in object reflectivity.