arXiv subjects

Ahmad Salmanogli

Publications and source records attributed to Ahmad Salmanogli.

At least 19 recordsLinked to original sources

arXiv2026

Design of Qubit Readout Circuit for Purcell-Rate Suppression by Two-Path Interference

The Purcell effect, a common issue in qubit-resonator systems leading to both fidelity and nonclassicality losses is studied while its suppression is achieved using a novel qubit readout circuit design. Our approach utilizes a unique coupling architecture in which, the qubit first interacts with a filter resonator before coupling to the readout resonator. This configuration enables precise control over the Purcell decay rate and ac Stark factor without impacting on measuring time. The mentioned factor is highly sensitive to the coupling strength between the readout resonator and the filter, meaning that the factor adjustment directly impacts the qubit state detection. A major advantage of this design is that tuning the resonator-filter coupling strength is relatively straightforward, offering flexibility in fine-tuning ac Stark factor. This work extensively analyzes the system using full quantum mechanical theory, deriving the total Hamiltonian and investigates mode dynamics via quantum Langevin equations. Key parameters influencing the nonclassicality of output signals are also explored through quantum correlation metrics, including symplectic eigenvalues, quantum discord, and classical discord. The main goal is to find any compromises exsting between the ac Stark factor increasing and the quantum correlation created in the readout circuit. By optimizing the critical factors, by which the ac Stark factor mainly affected, the proposed design not only improves the distinguishability of the qubit states but also ensures robust nonclassicality in the output signals. Results demonstrate the potential of the proposed system to bridge the gap between a high fidelity readout and quantum correlation preservation in scalable quantum architectures.

quant-ph↗

arXiv2026

A Unified Quantum Neural Network Framework for Hamiltonian Learning and Emulation of Unknown Quantum Systems

Accurate identification of unknown quantum systems is essential for quantum computing, sensing, and control because the Hamiltonian governs quantum state evolution. This work proposes a QNN based framework for black box Hamiltonian learning and quantum system emulation using full density matrix trajectory learning. Unlike approaches based only on final states or selected observables, the method exploits the complete temporal evolution of the density matrix under Lindblad dynamics. A synthetic dataset of physically admissible Hamiltonians and dissipation parameters is generated to emulate experimental measurements. The QNN learns a nonlinear mapping from control inputs to a 32-dimensional Hamiltonian coefficient vector, enabling reconstruction and differentiable emulation of the unknown system. Chirped excitation and randomized initial quantum states are incorporated to improve robustness and provide richer dynamical information. Performance is evaluated using trajectory density loss, quantum-state fidelity, and trace distance. Randomized initialization improves state-level reconstruction, increasing fidelity to 0.929 for the single qubit benchmark and 0.787 for the unknown system, while reducing trace distance to 0.124 and 0.316, respectively. In contrast, chirped excitation primarily improves optimization by accelerating convergence and reducing trajectory density loss. Finally, the learned Hamiltonian is mapped onto a physical two qubit bus resonator architecture in the dispersive regime, yielding key circuit parameters including transmon capacitances, Josephson inductances, qubit separation, and bus-resonator length. The framework therefore establishes a data-driven pathway from black box quantum system identification to physical quantum emulation, with potential applications in quantum digital twin modeling.

quant-ph↗

arXiv2026

Implementing Grover Algorithm on Quantum Chip Architecture Optimized with QGHNN for Fidelity and Entanglement Preservation

This study introduces a superconducting quantum chip architecture designed to simultaneously preserve entanglement and readout fidelity, addressing one of the key trade-offs in the development of scalable quantum hardware. In conventional quantum circuits, strong qubit qubit coupling enhances entanglement but often leads to undesired crosstalk, dephasing, and reduced measurement fidelity. To mitigate these effects, we propose a hybrid multiqubit configuration consisting of nine transmon qubits organized into interior and exterior groups, interconnected via a flux tunable qubit and a network of distributed resonators. The interior qubits along with tunable qubit form an entanglement core, while the exterior qubits operate in the dispersive regime under large detuning to enable readout. The degree of entanglement can be dynamically tuned by adjusting the coupling between the central tunable qubit and the interior qubits. The total Hamiltonian includes all significant coupling contributions, encompassing effective exchange interactions among interior and exterior qubits, as well as their mediated couplings through interface resonators. By numerically solving the complete Hamiltonian alongside the Lindblad master equation, the system dynamics are characterized, allowing evaluation of both spectroscopic features and separation fidelity. Simulation results demonstrate that the proposed design maintains strong entanglement by creating the avoided-crossing region while sustaining measurement fidelity around 0.995 under realistic noise conditions. These findings confirm that entanglement strength and readout fidelity can be co-optimized within a single, reconfigurable architecture, establishing a viable route toward high-performance and scalable superconducting quantum processors.

quant-ph↗

arXiv2025

Technical Review on RF-Amplifiers for Quantum Computer Circuits: New Architectures of Josephson Parametric Amplifier

Josephson Parametric Amplifiers (JPAs) are key components in quantum information processing due to their ability to amplify weak quantum signals with near-quantum-limited noise performance. This is essential for applications such as qubit readout, quantum sensing, and communication, where signal fidelity and coherence preservation are critical. Unlike CMOS and HEMT amplifiers used in conventional RF systems, JPAs are specifically optimized for millikelvin (mK) cryogenic environments. CMOS amplifiers offer good integration but perform poorly at ultra-low temperatures due to high noise. HEMT amplifiers provide better noise performance but are power-intensive and less suited for mK operation. JPAs, by contrast, combine low power consumption with ultra-low noise and excellent cryogenic compatibility, making them ideal for quantum systems. The first part of this study compares these RF amplifier types and explains why JPAs are preferred in cryogenic quantum applications. The second part focuses on the design and analysis of JPAs based on both single Josephson junctions and junction arrays. While single-junction JPAs utilize nonlinear inductance for amplification, they suffer from gain compression, limited dynamic range, and sensitivity to fabrication variations. To overcome these challenges, this work explores JPA designs using Josephson junction arrays. Arrays distribute the nonlinear response, enhancing power handling, linearity, impedance tunability, and coherence while reducing phase noise. Several advanced JPA architectures are proposed, simulated, and compared using quantum theory and CAD tools to assess performance trade-offs and improvements over conventional designs.

quant-ph↗

arXiv2025

Design of Advanced Readout and System-on-Chip Analog Circuits for Quantum Chip

In this work, we design an advanced quantum readout architecture that integrates a four qubit superconducting chip with a novel parametric amplifier ended with analog front-end circuit. Unlike conventional approaches, this design eliminates the need for components such as Purcell filters. Instead, a Josephson Parametric Amplifier is engineered to simultaneously perform quantum-limited signal amplification and suppress qubit energy leakage. The design features a tailored gain profile across C-band, with sharp peaks (24 dB) and troughs (0 dB), enabling qubit frequencies to align with gain minima and resonator frequencies with gain maxima.

quant-ph↗

arXiv2024

Design of a Specialized Low Noise Amplifier for Enhancing Non-Classicality in Quantum Applications

In this study, we present the design and analysis of a Low Noise Amplifier tailored specifically for quantum applications. We selected the HEMT for its unique noise reduction properties, crucial for quantum engineering. The main goal is to minimize the noise figure within the C-band frequency range (4-8 GHz) to induce nonclassicality in quantum signals. While achieving a noise figure of less than 0.065 dB within this band, we recognized the trade-off with gain, mitigated by incorporating additional stages to maintain noise figure at optimal levels. Quantum analysis of the circuit, employing a simplified model of HEMT due to its complexity, revealed insights into its nonlinear properties and interactions between circuit components and environmental factors. Leveraging Qutip toolbox in Python, we conducted time-evolution analysis of the system, revealing the circuit's behavior as an open quantum system under cryogenic conditions. Our investigation extends to quantifying quantum correlation (quantum discord) and its relationship with noise figure, posing important questions regarding the direct impact of its minimization on circuit nonclassicality at cryogenic temperatures. This comprehensive study sheds light on the intricate interplay between circuit design, and its influence on the relationship between the noise figure and quantum correlation.

quant-ph↗

arXiv2024

Technical Review of Four Different Quantum Systems: Comparative Analysis of Quantum Correlation, Signal-to-Noise Ratio, and Fidelity

This technical review examines the different methods and approaches have been used to create microwave modes of quantum correlation. Specifically, we consider the electro-opto-mechanical, optoelectronics, 4-coupled qubits, and InP HEMT coupled with two external oscillator methods, and evaluate their effectiveness for quantum applications. Since these systems are open quantum systems, they interact with their own environment medium and thermal bath. To ensure an accurate comparison, we analyzed all of the systems using the same criteria. Thus, at first all systems are introduced briefly, then the total Hamiltonian is theoretically derived, and finally, the system dynamics are analogously analyzed using the Lindblad master equation. We then calculate the quantum correlation between cavity modes, signal-to-noise ratio, and fidelity for each system to evaluate their performance. The results show that the strength and nature of the calculated quantities vary among the systems. An interesting result is the emergence of mixing behavior in the quantum correlation and signal-to-noise ratio for systems that use different cavities. It also identified a significant similarity between the 4-coupled qubits and InP HEMT coupled with external oscillators methods, where an avoided-level crossing occurs in the quantum correlation. Additionally, the study results reveal a high consistency between the signal-to-noise ratio and classical discord.

quant-ph↗

arXiv2024

Design of Ultra-Low Noise Amplifier for Quantum Applications (QLNA)

The present article primarily focuses on the design of an ultra-low-noise amplifier specifically tailored for quantum applications. The circuit design places a significant emphasis on improving the noise figure, as quantum-associated applications require the circuit's noise temperature to be around 0.4 K. This requirement aims to achieve performance comparable to the Josephson Junction amplifier. Although this task presents considerable challenges, the work concentrates on engineering the circuit to minimize mismatch and reflection coefficients, while simultaneously enhancing circuit transconductance. These efforts aim to improve the noise figure as efficiently as possible. The results of this study indicate the possibility of achieving a noise figure of approximately 0.009 dB for a unique circuit design operating at 10 K. In a departure from traditional approaches, this study employs quantum mechanical theory to analyze the circuit comprehensively. By employing quantum theory, the researchers derive relationships that highlight the crucial quantities upon which the circuit design should focus to optimize the noise figure. For example, the circuit's gain power, which depends on the circuit's photonic modes, is theoretically derived and found to affect the noise figure directly. Ultimately, by merging quantum theory with engineering approaches, this study successfully designs a highly efficient circuit that significantly minimizes the noise figure in a quantum application setting.

quant-ph↗

arXiv2024

Design of Fully Integrated 45 nm CMOS System-on-Chip Receiver for Readout of Transmon Qubit

This study unveils a comprehensive design strategy, intricately addressing the realization of transmon qubits, the design of Josephson parametric amplifiers, and the development of an innovative fully integrated receiver dedicated to sensing ultra-low-level quantum signals. Quantum theory takes center stage, leveraging the Lindblad master and quantum Langevin equations to design the transmon qubit and Josephson parametric amplifier as open quantum systems. The mentioned quantum devices engineering integrated with the design of a fully integrated 45 nm CMOS system-on-chip receiver, weaves together a nuanced tapestry of quantum and classical elements. On one hand, for the transmon qubit and parametric amplifier operating at 10 mK, critical quantum metrics including entanglement, Stoke projector probabilities, and parametric amplifier gain are calculated. On the other hand, the resulting receiver is a symphony of high-performance elements, featuring a wide-band low-noise amplifier with a 0.8 dB noise figure and ~37 dB gains, a sweepable 5.0 GHz sinusoidal wave generator via the voltage-controlled oscillator, and a purpose-designed mixer achieving C-band to zero-IF conversion. Intermediate frequency amplifier, with a flat gain of around 26 dB, and their low-pass filters, generate a pure sinusoidal wave at zero-IF, ready for subsequent processing at room temperature. This design achieves an impressive balance, with low power consumption (~122 mW), a noise figure of ~0.9 dB, high gain (~130 dB), a wide bandwidth of 3.6 GHz, and compact dimensions (0.54*0.4 mm^2). The fully integrated receiver capability to read out at least 90 qubits positions this design for potential applications in quantum computing. Validation through post-simulations at room temperature underscores the promising and innovative nature of this design.

physics.app-ph↗

arXiv2023

Quantum Parametric Amplification and NonClassical Correlations due to 45 nm nMOS Circuitry Effect

This study unveils a groundbreaking exploration of using semiconductor technology in quantum circuitry. Leveraging the unique operability of 45 nm CMOS technology at deep cryogenic temperatures (~ 300 mK), a novel quantum electronic circuit is meticulously designed. Through the intricate coupling of two matching circuits via a 45 nm nMOS transistor, operating as an open quantum system, the circuit quantum Hamiltonian and the related Heisenberg-Langevin equation are derived, setting the stage for a comprehensive quantum analysis. Central to this investigation are three pivotal coefficients derived, which are the coupling between the coupled oscillator charge and flux operators through the internal circuit of the transistor. These coefficients emerge as critical determinants, shaping both the circuit potential as a parametric amplifier and its impact on quantum properties. The study unfolds a delicate interplay between these coefficients, showcasing their profound influence on quantum discord and the gain of the parametric amplifier. Consequently, the assimilation of 45 nm CMOS technology with quantum circuitry makes it possible to potentially bridge the technological gap in quantum computing applications, where the parametric amplifier is a necessary and critical device. The designed novel quantum device serves not only as a quantum parametric amplifier to amplify quantum signals but also enhances the inherent quantum properties of the signals such as non-classicality. Therefore, one can create an effective parametric amplifier that simultaneously improves the quantum characteristics of the signals. The more interesting result is that if such a theory becomes applicable, the circuit implemented in the deep-cryogenic temperature can be easily compatible with the next step of circuitry while keeping the same electronic features compatibility with the quantum processor.

quant-ph↗

arXiv2023

Quantum Correlation at Zero-IF: InP HEMT Circuitry Effect

The quantum correlation between microwave modes in an RF electronic circuit is analyzed and studied. An open quantum system operating at 4.2 K is designed in which InP HEMT as the nonlinear component couples two external oscillators to each other. The quantum theory is applied to completely analyze the system, by which the related quantum Hamiltonian containing all noise sources is derived. The Lindblad Master equation is used to analyze the time evolution of the expanded closed system that covers the environmental effects. In the following, the state of the system defined is determined in terms of the ensemble average state using the density matrix; then, the ensemble average of the different operators is calculated. Accordingly, the covariance matrix of the quantum system is derived, and the quantum discord as a key quantity to determine the quantum correlation is calculated. As an interesting point, the results show that InP HEMT mixes two coupling oscillator modes so that the quantum correlation is created at different frequency productions such as 2nd, 3rd, and 5th. The harmonics suitable for sampling and digitalization is the zero-IF (downside of 2nd harmonics) band at which the quantum correlation is generated. Another point is that there is no quantum correlation at the frequency resonance of each oscillator coupled to InP HEMT.

quant-ph↗

arXiv2022

Quantum Correlation of Microwave Two-mode Squeezed State Generated by Nonlinearity of InP HEMT

This study significantly concentrates on cryogenic InP HEMT high-frequency circuit analysis using quantum theory to find how the transistor nonlinearity can affect the quantum correlation of the modes generated in the circuit. Firstly, the total Hamiltonian of the circuit is derived, and the dynamic equation of the motion contributed is examined using the Heisenberg-Langevin equation. Using the nonlinear Hamiltonian, some components are attached to the intrinsic internal circuit of InP HEMT to fully address the circuit characteristics. The components attached are arisen due to the nonlinearity effects. As a result, the theoretical calculations show that the states generated in the circuit are mixed, and no pure state is produced. Accordingly, the modified circuit generates the two-mode squeezed thermal state, which means one can focus on calculating the Gaussian quantum discord to evaluate quantum correlation. It is also found that the nonlinearity factors (addressed as the nonlinear components in the circuit) can intensely influence the squeezed thermal state by which the quantum discord is changed. Finally, as the primary point, it is concluded that although it is possible to enhance the quantum correlation between modes by engineering the nonlinear components; however, quantum discord greater than unity, entangled microwave photons, seems a challenging task since InP HEMT operates at 4.2 K.

quant-ph↗

arXiv2022

Qubit Coupling to Reservoir Modes: Engineering the Circuitry to Enhance the Coherence Time

In this study, a circuitry model of the coupling of a qubit to reservoir modes is defined to clearly determine the effect of the reservoir modes on the qubit decay and dephasing rates. The main goal is to theoretically calculate the dephasing and decay rate of a qubit, particularly due to the circuitry effect. Firstly, the Hamiltonian of the system (coupling of a qubit to the reservoir modes) is defined and used to derive the time evolution of the density matrix for the qubit energy levels. By calculating the qubit level density evolutions, one can estimate at which frequency the maximum coupling occurs and, in addition, knows about the role of the electromagnetic bias in the qubit. Secondly, the qubit decay rate is theoretically derived. The results show that the decay rate is strongly affected by circuitry elements such as the qubit capacitor and, more importantly, the coupling capacitor between the qubit and the reservoir modes. As the main result, it is shown that the slight decrease in the coupling capacitors significantly affects the relaxation time even more than the qubit capacitor. Consequently, the dephasing rate, which is the effect of the reservoir modes on the transition frequency of the qubit, is theoretically examined using the Heisenberg-Langevin equation. Finally, by transforming the Heisenberg-Langevin equations into the Fourier domain, the number of photons of the qubit due to coupling to reservoir modes are calculated. This is considered to be the photons generated in the qubit owing to the noise effect. This term significantly influences the qubit coherence time.

quant-ph↗

arXiv2022

Squeezed States Generation using Cryogenic InP HEMT Transistor Nonlinearity

This study focuses on generating and manipulating squeezed states with two external oscillators coupled by an InP HEMT transistor operating at cryogenic temperatures. First, the small-signal nonlinear model of the transistor at high frequency at 5 K is analyzed using quantum theory, and the related Lagrangian is theoretically derived. Subsequently, the total quantum Hamiltonian of the system is derived using Legendre transformation. The Hamiltonian of the system includes linear and nonlinear terms, by which the effects on the time evolution of the states are studied. The main result shows that the squeezed state can be generated owing to the nonlinearity of the transistor, and more importantly, it can be manipulated by some specific terms introduced in the nonlinear Hamiltonian. In fact, the nonlinearity of the transistors induces some effects such as capacitance, inductance, and second-order transconductance, by which the properties of the external oscillators are changed. These changes may lead to squeezing or manipulation of the parameters related to squeezing in the oscillators. In addition, it is theoretically derived that the circuit can generate two-mode squeezing. Finally, second-order correlation (photon counting statistics) is studied as a complementary task, and the results demonstrate that the designed circuit exhibits antibunching, where the quadrature operator shows squeezing behavior.

quant-ph↗

arXiv2022

Entangled Microwave Photons Generation using Cryogenic Low Noise Amplifier (Transistor Nonlinearity Effects)

This article mainly focuses on one of the important phenomena in the quantum realm called entanglement. It is clear that entanglement created due to the nonlinearity property has been arisen by some different methods. This study in contrast uses a unique approach in which a cryogenic low noise amplifier is designed and using the transistor nonlinearity effect (third-order nonlinearity) entangled microwave photons are created. It is supposed that the low noise amplifier contains two coupled oscillators resonating with different frequencies. The mentioned oscillators are coupled to each other through the gate-drain capacitor and nonlinear transconductance as an important factor by which the entangled microwave photons are strongly manipulated. For entanglement analysis, the Hamiltonian of the system is initially derived, then using the dynamic equation of motion of the designed amplifier the oscillator's number of photons and also the phase sensitive cross-correlation factor are calculated in Fourier domain to calculate the entanglement metric. As a main conclusion, the study shows that the designed low noise amplifier using nonlinearity of the transistor has the ability to generate the entangled microwave photons at very low intrinsic transconductance and more importantly when the noise figure is strongly minimized. Additionally, a cryogenic low noise amplifier is designed and simulated to verify that it is possible to achieve an ultra-low noise figure by which the probability of the generation of the entangled microwave photons is increased.

quant-ph↗

arXiv2021

Entanglement Engineering by Transmon Qubit in a Circuit QED

this study significantly emphasizes on the entanglement engineering using a transmon qubit. A transmon qubit is created with two superconducting islands coupled with two Josephson Junction embedded into a transmission line. The transmon qubit energies are manipulated through its coupling to the transmission line. The key factor here is the coupling factor between transmission line and qubit by which the quantum features of the system such as transmon decay rate, energy dispersion, and related coherence time are controlled. To complete knowledge about the design, the system is quantum mechanically analyzed and the related Hamiltonian is derived. Accordingly, the dynamics equation of motions is derived and so the energy dispersion and the coupled system coherence time are investigated. The system engineering should be established in such a way that satisfies the energy dispersion and the coherence time. However, to analyze the entanglement between modes, it needs to calculate the number of photons of the transmission lines and the transmon qubit, and also the phase sensitive cross-correlation. The important section of this study emphasizes on engineering the coupling between the transmon qubit and transmission line to enhance the entanglement. The results show that around the Josephson Junction location where the more coupling is established the more entanglement between modes is created.

quant-ph↗

arXiv2021

An Exact Method using Quantum Theory to Calculate the Noise Figure in a Low Noise Amplifier

In this article, a low noise amplifier is quantum mechanically analyzed to study the behavior of the noise figure. The analysis view is changed from the classic to quantum, because using quantum theory produces some degrees of freedom, which may be ignored when a circuit is analyzed using a classical theory. For this reason, the associated Lagrangian is initially derived for the circuit and then using Legendre transformation and canonical quantization procedure the classical and quantum Hamiltonian are derived, respectively. Consequently, the dynamic equation of motion of the circuit is introduced by which all of the circuit measurable observations such as voltage and current fluctuations are calculated. As an interesting point of this study, the low noise amplifier is deliberately supposed as two oscillators connecting to each other sharing the mutual specifications and accordingly the voltage and current are expressed in terms of the oscillators photon number. As a result, one can analyze the critical quantity such as the noise figure in terms of the oscillators photon number and also the photons coupling between oscillators. The latter mentioning term is considered as a factor to engineering the amplifier critical quantities. Additionally, the considered circuit is designed and classically simulated to testify the derived results using the quantum theory.

quant-ph↗

arXiv2020

Optoelectronic based Quantum Radar: Entanglement Sustainability Improving at High Temperature

In this study, the main focus is laid on the design of the optoelectronic quantum illumination system to enhance the system performance, such as operation at high temperature and confinement of the thermally excited photons. The optomechanical based quantum illumination system has wieldy been studied, and the results showed that operation at high temperature is so crucial to preserve the entanglement between modes. The main problem is that the mechanical part has to operate with a low frequency with which a large number of thermally excited photons are generated and worsened the entanglement. To solve this problem, we focus on replacing the mechanical part with the optoelectronic components. In this system, the optical cavity is coupled to the microwave cavity through a Varactor diode excited by a photodetector. The photodetector is excited by the optical cavity modes and drives the current flow as a function of incident light drives the Varactor diode at which the voltage drop is a function of current generated by the photodetector. To engineer the system, the effect of some parameters is investigated. One of the critical parameters is the microwave cavity to the photodetector coupling factor. Our results indicate that this coupling factor induces a significant difference in the new design as compared to the optomechanical quantum illumination system. At some specific values of the coupling factor, the modes remained completely entangled up to 5.5 K and partially entangled around 50 K.

quant-ph↗