Optoelectronic based Quantum : Entanglement Sustainability Improving at High Temperature

Ahmad Salmanogli1,2 and Dincer Gokcen*1 1Faculty of Engineering, Electrical and Electronics Engineering Department, Hacettepe University, Ankara, Turkey 2Faculty of Engineering, Electrical and Electronics Engineering Department, Çankaya University, Ankara, Turkey Abstract— In this study, the main focus is laid on the linked to each other in such a way that the distance design of the optoelectronic quantum illumination between them is not a concern [5], [19]-[20]. Quantum system to enhance the system performance, such as use the fundamental advantage of the classical operation at high temperature and confinement of the radars, which is the efficient penetration in clouds and thermally excited . The optomechanical based fogs due to photons. Also, quantum radars quantum illumination system has wieldy been studied, using entangled microwave photons dramatically and the results showed that operation at high enhance the signal to noise ratio, resolution, and temperature is so crucial to preserve the entanglement probability of detection as compared with the non- between modes. The main problem is that the mechanical entangled photons [1], [2], [9]- [10]. It has been part has to operate with a low frequency with which a reported that all advantages of the quantum radar are large number of thermally excited photons are generated specifically devoted to the entanglement phenomenon. and worsened the entanglement. To solve this problem, Unfortunately, the entanglement is so fragile and we focus on replacing the mechanical part with the unstable, and also it is generally difficult to create and optoelectronic components. In this system, the optical preserve easily. In other words, the environment noise, cavity is coupled to the microwave cavity through a specifically thermal noise, can easily destroy the Varactor diode excited by a photodetector. The entangled states [12], [17]. The most common problem photodetector is excited by the optical cavity modes and that the quantum radar system deals with is the drives the current flow as a function of incident light propagation of the entangled microwave photons into drives the Varactor diode at which the voltage drop is a function of current generated by the photodetector. To the atmosphere to detect the target. Designers cannot engineer the system, the effect of some parameters is control the free space temperature, pressure, and investigated. One of the critical parameters is the interaction between incident light with solid particles. microwave cavity to the photodetector coupling factor However, one of the crucial factors is the temperature by which the thermally induced photons can easily (µc). Our results indicate that this coupling factor induces a significant difference in the new design as affect entangled microwave photons associated with compared to the optomechanical quantum illumination low-level energy. Also, the low-level energy of the system. At some specific values of the coupling factor, the microwave is another factor of the fragility of modes remained completely entangled up to 5.5 K and the entangled states utilized by a quantum radar. This partially entangled around 50 K. point has been investigated in more detail in some published works [9], [10]. These studies focused on Index Terms—Quantum theory; quantum illumination some parameters such as teleportation fidelity [10], system; optoelectronic; entanglement signal to noise ratio and error probability [9] in the quantum illumination system. Moreover, the effect of I. INTRODUCTION some critical parameters, such as quantum noise and In recent years, the idea of using quantum phenomena quantum Brownian noise, have been investigated for to enhance the performance of conventional sensors the entanglement. Another interesting study related to has come to the fore in many applications. Among the quantum illumination system has focused on the these applications, radar systems [1]-[4], enhancement generation of the entangled microwave photons using of the image resolution [5]-[7], design of quantum Josephson parametric converter (JPC) [11]. In this illumination systems [8]-[13], quantum work, the generated microwave mode is amplified to communication networks [14]-[15], increase of the facilitate the detection process. plasmonic photodetector responsivity [16], The critical point about the system discussed above is enhancement of the plasmonic system decay rate [17], the generation of entangled photons at very low improvement of Raman signals [18], and so forth can temperatures. In [9] and [10], the optomechanical be counted. Primarily, a quantum radar utilizes the system had been utilized in which the mechanical part entangled microwave photons to enhance the frequency is so small. That is the reason, by which the detection, identification, and resolution [1], [4], [9], thermally induced photons are dramatically increased [10]. In the entangled particles, two particles are and eventually confined the entangled photons.

Therefore, in the studies mentioned, the operational manipulate the non-classical correlation between MC temperature is restricted to 15 mK. In [11], a JPC has and OC modes. One of the factors relates to OC modes been utilized to generate entangled photons due to the coupling to PD by which the current generation rate is related nonlinearity in which the operating frequency defined. Another factor is the coupling between VD is in the range of GHz; nonetheless, the system and MC mode with which the microwave photons operating temperature is limited to 7 mK. properties are affected. The latter one is a capacitive In the study, we use the optoelectronics subsystem to coupling between the optoelectronic device and MC. generate the entangled photons. The mechanical part As a short conclusion, the entanglement between two from the traditional tripartite system [22]-[26] is removed, and instead, the optoelectronic components modes will be changed by engineering the mentioned are utilized to couple the microwave cavity modes to coupling factors. The subsystem illustrated in Fig. 1a the optical cavity modes [21]. One of the interesting is the only stage one can manipulate and engineer the points related to this system is the high operating entangled microwave photons; in the following stages frequency of the optoelectronic subsystem. This shown in Figs. 1b, 1c, and 1d, there are no degrees of significantly reduces the thermally induced photons freedom either to manipulate or to improve the and the associated noises. It is important to note that entanglement between modes. Since the MC modes the entanglement between modes is strongly improved are generated by the coupled systems which are via the utilization of optoelectronic components. entangled with the OC modes, they are propagated into Unlike [21], in which the same subsystems had been the atmosphere (attenuation medium) to detect the modeled using optical pressure effect on the target. The effects of atmosphere medium are analyzed photodetector, the system of our interest is analyzed quantum mechanically through considering the with the canonical conjugate method [27]-[29]. Therefore, in contrast to the former approach [21], the medium as a sequence of the beam splitter (BS) [27], new one provides some degrees of freedom to which is schematically depicted in Fig. 1b. Each beam elaborate on the system completely. splitter has two inputs as the incident wave (ci-1) and thermally generated photons (bi) and two outputs as II. THEORY AND BACKGROUND the noise (asi) and the desired output (ci). The thermally The schematic of the system is illustrated in Fig. 1 in induced photons highly depend on the temperature of which each stage of the design is depicted. It is clearly the atmosphere varying between 190~300 K. It shown in Fig. 1a that the laser light is initially coupled depends on the atmosphere height. The propagation of to an optical cavity (OC), and consequently, the entangled photons into the atmosphere drastically outcoming from OC excites the photodetector (PD). affects the entanglement between modes. We utilized a quantum dot (QD) photodetector to Consequently, the effect of the scattering from the enhance the current generation [16]. Therefore, the target is considered (Fig.1c). The propagated signals sensitivity of the system can be strongly increased. have some entangled photons as well as separable The current flowing through the PD is a function of the ones; it is shown that the amount of the entangled excitation wave frequency. This indicates the current photons incident on target are strongly depended on flow highly depends on the OC modes. The current the atmospheric condictions. So the incident fields flow induces a voltage drop across the Varactor diode containing entaged and separable photons interact (VD) by which the capacitance of the VD is with the target atom’s field. The interaction between manipulated. Thus, the VD capacitance is a function two fields, here, is studied via the sequence of BS of flowing current, which was shaped as a function of containing two inputs as thermally induced photons OC modes. In other words, the VD capacitance (bti) and cai as the propagated signals and an output, implicitly depends on OC modes. As clearly shown in which is the scattered photons. The scattered photons Fig. 1a, by changing VD capacitance, the MC resonant amplitude and frequency are fully affected by the frequency is manipulated. Therefore, the MC modes target’s materials properties. In other words, it is the will be affected by the OC modes through coupling PD target’s field that manipulates the incident photons and VD. In this configuration, there are two crucial properties, and especially the entanglement between coupling factors that one can maneuver on them, to modes are strictly affected.

Fig. 1 Schematics of the optoelectronic based quantum illumination system; a) optical cavity coupled to microwave cavity through the optoelectronic device and Varactor diode, b) modeling of the attenuation medium (atmosphere) effect on the microwave cavity modes using BS, c) modeling of the target scattering using BS, d) modeling of the scattering signal transmission through the attenuation medium (atmosphere) using BS and finally the detection, e) photodetector from a top view; it illustrates the interaction of light (photons from OC) with QDs and shows an increment in charge carriers.

Finally, in Fig. 1d, the backscattered photons from the energy levels and even the effect of QD to generate target experience the atmosphere effect in the same more carriers are represented. way with Fig. 1b. However, there is a critical In the system illustrated in Fig. 1, most of the factors difference between them; in Fig. 1b the input is cω that can affect the entanglement between modes are containing the most entangled photons while in ct, discussed and modeled using BS. In the following, which is the scattered photons, most of the scattered theoretical analyses of the system will be presented in photons lost their entanglement. That means the such a way that one can fully understand the parts or atmosphere effect on entanglement properties are so stages of the system in detail. crucial in Fig. 1d. Also, the PD top view is depicted in After a short discussion about the general operation of Fig. 1e for better illustration. In this schematic, the QD the system illustrated in Fig. 1, the quantum radar

system (subsystem shown in Fig. 1a) is theoretically depletion layer width in the steady-state, and ℏ is the analyzed using the canonical conjugate method [13]. reduced Plank’s constants. and moreover µc = ’ The total Hamiltonian of the system containing OC, C (x)/C0. From MC-PD interaction Hamiltonian, MC, optoelectronics (photodetector-PD), and also the coupling factor is concluded as goω = (µcωω/2d) coupling between subsystems given by: ×√(ℏ/ωegmeff); this is such an important factor in  quantum radar system by which the non-classical HEA0 ()222  OCc 2 correlation between modes can be manipulated. Here in this study, by manipulation of this factor, we intend 2 P 1 22 to preserve the entanglement between modes even at HmXPDeffeg 2 22meff high temperatures. Also, gop = √(ωegαc /2ωcε0meff) is the OC-PD coupling rate. In Eq. 2, Hoc and HMC 22 QCv  dd (1) contain the field Hamiltonian plus cavity driving by HQMC  22CLC00 the external source. In this system, using the first-order AP perturbation theory, one can calculate the coupling HOCPDc   coefficient between OC and PD in unit volume as [16]: meff c 2 2 ggLopJegeg().() CxQ'()  0Vm (3) HCvQXMCPDdd 2  C0 2 2mc0eff  c 2 c  gLJegeg().() where (A, E), (X, P), and (Φ, Q) are the operators for eg0 Vm the vector potential and electric field of OC, PD where µ, g (hω ), V , and L(ω ) are the dipole electron-hole position and momentum operators, and J eg m eg momentum, PD density of state, volume, and MC related phase and charge operators, respectively. Lorentzian function, respectively. Using Eq. 3 one Additionally, ε , α , ω , ω , L, v , C’(x), C , C and 0 c eg c d 0 d, determines the α which depends on the PD properties, m are the free space permittivity, OC-PD coupling c, eff so by manipulation of the optical properties of PD, it coefficient, PD gap-related frequency, OC angular is possible to change the coupling between OC and frequency, inductance, MC input driving field, PD. We want to use this factor as a critical case for variable capacitor, total capacitor, connection engineering the coupling between cavity modes. capacitor between v and LC circuit, and electron-hole d After the calculation of the system total Hamiltonian, effective mass, respectively. the dynamic equation of motion is defined using In the next step, one can define the conjugate variable Heisenberg-Langevin equation. Here, it is necessary to of the operators A, X, and Φ based on the classical consider the effect of the damping rate and noise due definition of the conjugate variables [28]. The to the interaction of the system with the medium. Also, contributed Hamiltonian in terms of the creation and using rotating wave approximation, the MC and OC annihilation operators is presented as: are driven at the frequencies ∆ω = ωω – ωoω and ∆c= ωc     ()() joc t j oc t – ωoc, respectively; moreover, PD is driven by ∆eg = HOC c a c a c  i E c[] a c e  ac e ωeg – ωc. Thus, the system dynamic equation of motion  22 is given by: Heg () P q MR2 x x   aiaccc  copig()2  xP  ccca in Ea       ()() joo t j t   HMC c  c   j| v d | C d [ c e  c  e ] 2C0 cic  ig()2   q  c Ec pin x (4)  2    c eg  HOC PD() a c ac P x qPxeg  xopg aa cc () 20meff c        PPqxp xegpin g  c cx b    c  H q c cs MC PD2dm x s where κc, γp, and κω are the optical cavity decay rate, eg eff photodetector damping rate, and microwave cavity (2) decay rate, respectively. In this equation, Δc, Δω, and + + where (ac , ac), and (cω , cω) are the creation and Δeg are the related detuning frequencies, and Eω = annihilation operators for the optical and microwave vdCd√(ωω/2ћC0) and Ec = √(2Pcκc/ћωoc) where Pc is the cavities, respectively. Also, ωoc is the input laser OC excitation power [22]- [26]. Also, bin is the angular frequency; (Px, qx) refers to the momentum quantum noise acting on PD, and ain and cin are input and position normalized quadrature operator; Ec is the noises because cavities interact with the environment. OC cavity input driving rate; d stands for VD capacitor

A simple way to calculate the entanglement for of modes around the steady-state points (As, Ps, Xs, and continuous modes is to select a fixed point that OC and Cs) are given by: MC are driven and worked. Under this condition, the  driven field is so strong, and also the coupling constant aiaigApPaascccopsxsccin (){}2 between OC, PD, and MC, PD are so small; therefore,  cicigqCXcc (){}2 one can linearize the equation of motion by expanding  psscsin x around the steady-state field (driven field). Thus, it is   appropriate to focus on the linearization and calculate qpgaaxegxopcc  {} the quantum fluctuation around the semi-classical   * fixed point [22], [26]. To linearize the motion ppqgCcCcbxpxegpssin   x {} equation, the cavity modes are expressed as the (5) composition of a constant and a fluctuating part as ac The interaction among cavities, e.g., OC with PD and = As+δac, cω = Cs+δcω, qx = Xs+δqx, and Px = Ps+δpx, MC with PD can generate CV entanglement, such as where the capital letter with subscript “s” denotes the the quantum correlation between quadrature operator fixed point, and also δ indicates the fluctuation part. of the cavity fields [22]-[26]. Therefore, in the In the steady-state condition, for Re{As}>>1 and following, we need to express the OC and MC fields |Cs|>>1 by which the stability condition is satisfied, the quadrature fluctuation by a matrix form as: dynamic of motion around the fixed point can be safely linearized. Therefore, the quantum fluctuations   qx 02000 egop g 0  q   x   px egpp srp si  0022 g Cg C bin  px  in (6) 0200 g Ag P    2ccX  X c op sicc op s  X c     2Y in 0200 g op Ag src P op sc  Yc cc Yc   in   X 2X 2000g p Cg sip s q     X  Y in  2Y  2000gp Cg srp  sq     Y  

Ai,j u(0) n(t)

in in in in In Eq. 6, δXc , δYc , δXω , and δYω are the system operating temperature (subsystem illustrated in quadrature operator of the related noises. The solution Fig. 1a), respectively. Solving Eq. 6 gives the cavities of Eq. 6 yields to a general form as u(t) = exp(Ai,jt)u(0) mode fluctuation, then one can calculate the + ∫(exp(Ai,js).n(t-s))ds, where n(s) is the noise column entanglement between the modes. Here in this system, matrix. The input noises obeying the correlation we specifically focus on the entanglement between OC function [22], [26] and can be expressed as: and MC modes is so critical. Such bipartite entanglement can be quantified through Symplectic * a ininc( s )( asNs ')[ ( s ) 1] (') eigenvalue given by [30], [31]: * 1 as ininc( a )( sNs ')[ ( s )] (')    2  2det(  ) , * 2 (8) cinin ( s )( csNs ')[ ( s ) 1] (') (7)  det(ABC )  det( )  2det( ) * csinin ( c ) sNs ( ')[ s ( )] (') Using Eq. 8, justify that if 2η >= 1, the considered * bininm ( s )( b ')[ sNs () s1] (') modes are purely separable; otherwise, for 2η < 1 , two modes are entangled [31]. Also, in Eq. 8, A, B, and C b * ( s ) b ( sNs ')[ ()] s (') ininm are 2×2 correlation matrix elements [A, C; CT, B] -1 where N(ω) = [exp(ћω/kBTc)-1] is the equilibrium which can be presented, as an example, for OC-MC mean of the thermal photon numbers of different modes as: modes, and kB and Tc are the Boltzmann’s constant and

22  XXXYYXXY cccccccc    0.5 A   0.5 XYYXXYYY     22 cccccccc (9)  XXXYYXXY 22    0.5 B   22 0.5 YXXYYXYY    

0.5XXc  XXXXXYYXXY ccccc    0.5 C   0.50.5 YXXYYXYcccccc    YYYYY  

In order to study the entanglement between OC and briefly investigated from a theoretical perspective. MC modes, it is necessary to calculate the expectation However, one can consider [13] to study in detail value of the quadrature modes operators (e.g., <δXc>, about the mentioned effects. 2 2 <δXω>, <δXc >, <δXω >, etc.). First of all, we considered the effect of the attenuation Up to now, the system dynamics equation of motion is medium, schematically illustrated in Fig. 1b, as a lossy analytically derived using the canonical conjugate medium on the entangled modes cω propagating into method and Heisenberg-Langevin equations, and also the medium. Symplectic eigenvalue was used as a criterion to In this study, the atmosphere medium is considered as analyze the entanglement between two modes. After a package involving the scattering centers. These that, as given in the procedure illustrated in Fig. 1, we scattering centers can be modeled with BS using have to apply the effect of the attenuation medium, and quantum electrodynamic, as shown in Fig. 1b. The scattering from a target on the outcoming propagated modeling starts with the attenuation medium th photons. As the main goal of this study, the subsystem scattering agents in which for j BS, the input is (caωj, in Fig. 1a should be designed in such a way that other bj), and the output is (caω(j+1), asj). Therefore, the effects such as atmosphere and scattering from the continuous form using the attenuation medium’s target are not supposed to distort the entanglement complex coupling coefficient satisfying |t(ω)|2+|r(ω)|2 between modes completely. In the following, the = 1 where t(ω) and r(ω) are the transmission and impact of atmosphere and scattering from the target is reflection, can be expressed as:  R [(iKatmRiKatmR )][( )]()atmatm  z  cecidzaatm( )( ebz )2( )( , )   (10) 0 where ca(ω), Katm and κatm(ω) are the attenuation electrodynamics is utilized to model the scattering medium output mode operator, the real part of the effect. The model to analyze the reflection effect is wave vector, and imaginary part of the wave vector, given in Fig. 1c. The reflection from a target, in the respectively. The scattering agents exponentially quantum picture, can be defined as the scattering from attenuate the input mode operator and also introduce the target atoms. This process describes the interaction the effect of the noise operator expressed in the second between the electromagnetic quantum field with the part. In the same way, it is possible to examine the quantum field of atoms. During the scattering from the entanglement between two modes (ca(ω), ac) using Eq. target, the thermally excited photons play an important 8. role through which the entanglement behavior is Another critical factor in a quantum radar is the effect strongly affected. To describe the process, jth BS is of the reflection from the target, which can destroy the considered as a reflection agent, and the related entangled states. In the same way considered for the expression between the input and output operators is attenuation medium effect, the quantum given in the continuous form as: zt   ()zzt  [iKt zt ] [ iKt  t (  )] [ iKt   t (  )] z t (11) ct()() te   2()  t   zdzte t  ()  ci a ()    t ()   ze t b t ()  0 where ct(ω), Kt, and κt(ω) are target’s scattering output excited photons in the second term in Eq. 12 strongly mode operator, the real part of the wave vector, and distorts the entanglement. the imaginary part of the wave vector, respectively. In After the calculation of the reflection from the target, this equation, the first term handles the direct effect of the reflected photons are scattered into the atmosphere the target’s imaginary part of the dielectric constant, medium. So, it is necessary to apply the atmosphere while in the second term, the impact of the thermally effect once again to complete the processes in excited photons is taken into account. In other words, quantum radar. In this study, we ignore studying the this equation expresses that the amplitude of the entanglement after detection; however, one can refer incident wave ca(ω) is dramatically decreased. More to [33],[34] to fully understand about the detection importantly, the phase raised due to the thermally effect and the related quantities such as signal to noise ratio, error probability and so forth.

In the following, the simulation results are detailed, of the atmosphere and scattering from the target can and a comprehensive discussion about how the not be controlled; nonetheless, it is possible to define optoelectronics components in Fig. 1a can enhance the and design a suitable system (Fig. 1a) to generate the quantum radar system performance to create the entangled states at high temperatures. By this, we entangled photons at high temperature in contrast with intend to subside and decrease the harmful effects of a traditional tripartite subsystem utilized in the atmosphere and scattering from the target and preserve quantum illumination system [22]-[26]. the entanglement.

III. RESULTS AND DISCUSSIONS Table .1 Constant data parameters used to simulate In this section, all of the simulation results are the system [9]- [10], [22]- [26] presented and discussed. The data used to model the λc 875 nm system illustrated in Fig. 1 is tabulated in Table. 1. vd 0.1 mV First, the effect of the temperature (Tc) as a very µc 0.0002 critical parameter on the entanglement between modes d 100 nm are studied. We considered two-mode entanglement Egap 1.42 ev -1 between ac & cω and ac & cb at µc = 0.0002 and Dtd = γp 32 ns -31 20 m where Dtd is the distance between transmitter and m0 9.109383×10 Kg detector. In this study, as shown in Fig. 1, ac is the OC meff 0.45*m0 mode, cω is the MC mode, and cb is the mode L 120 pH backscattered from the target and before detection. κc 0.08*ωref The results are shown in Fig. 2 in which 2η is depicted κω 0.02*ωref 6 versus PD detuning frequency. It is shown that there is ωref 2π*10 Hz C0 2.67 nF an entanglement around ∆eg~0, meaning PD is excited Cd 2 pF with a frequency ωc so close to ωeg. Fig. 2a shows that Pc 30 mW two modes remain entangled when the temperature Tc reached up to 3500 mK. Actually, there is an objection One of the critical factors to design such a system is MC-PD coupling factor g manipulated by µ . g can with the increase of T up to 3500 mK at the traditional ωp c ωp c be managed via other parameters such as d, m , ω tripartite system, which has been utilized to generate eff ω, and ωeg. The simulations are performed at Tc = 5000 entangled photons. The problem with increasing Tc up mK and Dtd = 20 m to study the entanglement of modes to 3500 mK is that thermally excited photons that can ac & cω (Fig. 3). It is clearly observable that by profoundly affect the entanglement between modes. increasing the coupling factor of MC and PD, the However, when the MC generated modes are entanglement between states is sharply increased. In propagated into the atmosphere to detect the target, fact, this factor creates a significant difference signal characteristics are not known, and there is between this work and others [9]-[10], [22], [26] in actually no control on signals. The effects of the which the traditional tripartite systems have been used. atmosphere and scattering from the target are studied For better illustration, the critical region of the figure using Eqs. 10 and 11, and the results are shown in Fig. is zoomed in and shown as an inset figure. Eventually, 2b. Accordingly, establishing entangled modes at it is possible to design a system to preserve the entangled states when the operating temperature is higher temperature T > 1000 mK becomes negligible, c increased. In the following, it will be shown that the the backscattering signals turn out to be completely generation of entangled photons at a higher separable. Thus, we should care about the subsystem temperature can preserve the entangled states at harsh at which the entangled photons are created. The effect atmospheric conditions.

Fig. 2 Temperature effect on entanglement between (a) ac & cω, (b) ac & cb at µc = 0.0002 and Dtd = 20 m, κatm = -6 2*10 1/m, κt = 18.2 1/m.

Fig. 3 MC-PD coupling effect on entanglement between ac & cω at Tc = 5000 mK and Dtd = 20 m The other vital parameter studied in this work is thermally excited photons will be increased transmitter-detector (Dtd) distance shown in Fig. 4. In significantly. This leads to decreasing the this study, the system operating temperature is entanglement between modes. Fig. 4d shows that, supposed to be around 1000 mK and for different Dtd, when the distance is increased to 2000 m, the the entanglement between different modes, such as ac entanglements between ac & ca, ac & ct, and ac & cb & cω, ac & ca (attenuation medium effect), ac & ct leak away entirely, and the input photons for the (target’s scattering effect), and ac & cb (backscattering detector are fully separable. It is contributed to the photons and then propagation into the atmosphere), fragility of the entangled states that are easily affected are studied. According to Eqs. 10 and 11, by increasing by the thermally excited photons and noise. the distance between transmitter and receiver, the

Fig. 4 Transmitter-detector (Dtd) distance effect on entanglement between different modes at µc = 0.0002, Tc = 1000 -6 mK, κatm = 2*10 1/m, κt = 18.2 1/m. In the following, we will consider two figures in which the correlation between modes after propagation into the effect of Tc at different modes of quantum radar is the atmosphere and scattering from the target. To studied. These results can be regarded as a significant confirm this point, one can consider Fig. 6 in which all contribution of this article to the quantum simulation conditions are the same as Fig. 5 except µc, entanglement and quantum illumination systems. The which controls the coupling strength. According to foundation of this study is the design of a system in Fig. 6, especially the backscattering modes ac & cb, which entanglement between modes can be preserved remained entangled even when the temperature is at high temperatures. We focused on the MC-PD increased up to 50 K and 150 K at some detuning coupling factor through which one can manipulate the frequencies. Increasing the coupling between MC and non-classical non-correlation between modes. Fig. 5 PD, the generated modes become strongly non reveals that for weak coupling, all modes become classically correlated to each other, even though the separable when Tc is increased up to 3500 mK. It is propagation into the atmosphere and scattering from worthy of mentioning that the MC-PD coupling factor the target cannot force the entanglement to leak away. directly affects ac & cω, in which cω is propagated into Therefore, the entanglement between ac & cb is just the atmosphere. Thus, the change of the coupling contributed to the entanglement between ac & cω, factor between MC and PD can implicitly manipulate which is established at a very high temperature.

-4 -6 Fig. 5 Temperature effect on entanglement between different modes at µc = 2*10 , and Dtd = 20 m, κatm = 2*10 1/m, κt = 18.2 1/m. The entangled region in Fig. 6 is depicted with the photocurrent flowing. The factor µc is a critical factor dashed circle. Moreover, for better illustration, some that is manipulated implicitly through the OC modes. critical regions of figures are zoomed in and shown as While in the traditional tripartite system, the optical an inset figure. Fig. 6 illustrates that at a relatively high pressure generated by OC creates a displacement in temperature like 50 K, it is possible to generate the capacitor electrodes and induces the change in the entangled photons, and an entangled microwave capacitance. Additionally, working with a mechanical photon can propagate into the atmosphere, and the part confine the operational frequency by which the entangled photons can also be detected. thermally induced noises can be crucial and limit the Optoelectronic components thoroughly contribute to operating temperature [9-12]. all these exciting features and operating at high However, it is evident that increasing Dtd actively temperatures. In this study, the methodology used for destroys the entanglement between modes. It is coupling between MC and PD is entirely different as because, in the design of the system, we didn’t compared to the traditional tripartite systems [9-12], consider an amplifier to intensify the signals before which are designed based on the alteration of the propagation. The amplification of the entangled distance between the electrodes of the capacitor. In photons to generate more entangled photons is very this study, the width of the depletion layer formed in critical [11], [32]. It is challenging to achieve both VD determines the capacitance value. The change in frequency and momentum conservation after the the depletion layer width, leading to the shift of µc, amplification of the photons. So, we preferred to affects the voltage drop, which is created due to the design the quantum radar system without amplifier.

-4 Fig. 6 Temperature effect (Tc) on entanglement between different modes at µc = 3.09*10 , and Dtd = 20 m, κatm = -6 2*10 1/m, κt = 18.2 1/m. IV. CONCLUSIONS transmitted into the atmosphere to detect the target. In this study, an optoelectronic based quantum radar We theoretically derived the effect of the attenuation was designed, modeled, and analyzed. First, an medium and scattering from the target using a optoelectronic subsystem was designed to generate the sequential BS system to model the impact of the entangled photons. This subsystem was the most environment on the incident photons. Finally, critical part of our quantum radar, and it was analyzed entanglements between the different modes were using the canonical conjugate method. Using this simulated and presented. As a remarkable result, it was method enabled control over the coupling between shown that one could manipulate the MC-PD coupling MC and PD to manipulate the system to preserve the factor to effectively subside the temperature effect on entanglement between photons. Additionally, this the entanglement between OC mode and microwave method provided answers to questions such as which generated mode. The simulation results revealed that parameter specifically subsides the temperature effect at a temperature around 50 K, it was possible to on the system and so forth. Following the generation generate the entangled photons and make them of the entangled microwave photons, it was propagate into the atmosphere as an entangled

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[30] R. Simon, “Peres-Horodecki separability criterion Ahmad Salmanogli received his B.S. and M.Sc. for continuous variable system,” physical review degrees in Electrical Engineering and letter, vol. 84, pp. 2726-2729, 2000. Nano&Optoelectronics from Tabriz University. His [31] W. Ge, M. E. Tasgin, and M. S. Zubairy, major interests are Quantum electronics, “Conservation relation of nonclassicality and Quantum Plasmonic, Plasmonic-Photonic entanglement for Gaussian states in a beam splitter,” engineering, quantum optics, and plasmonic based Phys Rev A, vol. 92, pp. 052328-052336, 2015. nanosensor. [32] E. Pomarico, B. Sanguinetti, P. Sekatski, H. Dincer Gokcen (M’08) received the B.S. degree in Zbinden and N. Gisin, “Experimental amplification of electrical engineering from Yildiz Technical an entangled photon: what if the detection loophole is University in 2005, and Ph.D. degree in electrical ignored?”, New Journal of Physics, vol. 13, pp. engineering from University of Houston in 2010. He 063031-45, 2011. has been with National Institute of Standards and Technology, Globalfoundries, and Aselsan, before joining Hacettepe University as an Assistant Professor in 2016. His research interest includes nanofabrication, process engineering technologies, quantum devices, and sensors.