Mohsen Akbari

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

  1. Ahmad Salmanogli,
  2. Hesam Zandi,
  3. Mahdi Esmaeili,
  4. Abolfazl Eskandari,
  5. and Mohsen Akbari
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.
arxiv pdf

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

  1. Ahmad Salmanogli,
  2. Hesam Zandi,
  3. Mahdi Esmaeili Turan Poshti,
  4. M. Hossein Eskandari,
  5. Ertan Zencir,
  6. and Mohsen Akbari
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.
arxiv pdf

Purcell Rate Suppressing in a Novel Design of Qubit Readout Circuit

  1. Ahmad Salmanogli,
  2. Hesam Zandi,
  3. Saeed Hajihosseini,
  4. Mahdi Esmaeili,
  5. M. Hossein Eskandari,
  6. and Mohsen Akbari
The Purcell effect, a common issue in qubit-resonator systems leading to fidelity loss 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 linking 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.
arxiv pdf