Alp Sipahigil (Advisor)

Research advised by BSAC Co-Director Alp Sipahigil

Sipahigil Group:  List of Projects | List of Researchers

Micrometer-Scale Merged-Element Superconducting Qubits with Phonon Engineering

Leo Sementilli
2026
Spring 2026 BSAC Research Review Presentation View Presentation View Slides...

BPNX1053: Micrometer-Scale Merged-Element Superconducting Qubits with Phonon Engineering

Leo Sementilli
Kerry Yu
2026

Classical computing relies on large arrays of robust miniaturized bits. Similarly, the development of useful quantum computing requires millions of low-footprint error-tolerant qubits. Current state-of-the-art superconducting qubits are not compatible with this approach as they rely on large device areas to increase qubit lifetimes and reduce noise. This limits the practicality of building a scalable superconducting quantum computer given size constraint. We explore an alternative to this limitation, where we predict both orders-of-magnitude reduction in qubit footprint and...

BPNX1066: Tunable Ultrahigh-Impedance Superconducting Resonators for Quantum Transduction (New Project)

Tae Gyu Ahn
Zihuai Zhang
2026

Disordered superconductors provide access to a unique regime of superconducting quantum circuits due to their large kinetic inductance, strong intrinsic nonlinearity, and high characteristic impedance. These properties enable compact microwave structures with strong electric field confinement, opening new opportunities for engineered light–matter interactions in reduced footprints. We are developing a DC-tunable, high-impedance superconducting nanowire platform based on TiN, a strongly disordered superconductor. The large kinetic inductance of TiN nanowires enables characteristic...

Observation of Interface Piezoelectricity in Superconducting Devices on Silicon

Haoxin Zhou
Eric Li
Kadircan Godeneli
Zi-Huai Zhang
Shahin Jahabani
Kangdi Yu
Mutasem Odeh
Shaul Aloni
Sinead Griffin
Alp Sipahigil
2025

The evolution of superconducting quantum processors is driven by the need to reduce errors and scale for fault-tolerant computation. Reducing physical qubit error rates requires further advances in the microscopic modeling and control of decoherence mechanisms in superconducting qubits. Piezoelectric interactions contribute to decoherence by mediating energy exchange between microwave photons and acoustic phonons. Centrosymmetric materials like silicon and sapphire do not display piezoelectricity and are the preferred substrates for superconducting qubits. However, the broken...

Xiaoya Chen

Graduate Student Researcher
Electrical Engineering and Computer Sciences
Professor Alp Sipahigil (Advisor)
Ph.D. 2031 (Anticipated)

Xiaoya Chen is a Ph.D. student in Electrical Engineering and Computer Sciences at UC Berkeley, where she is advised by Alp Sipahigil in the Quantum Devices Group. Her research centers on superconducting quantum hardware. Xiaoya received her B.S. in Electrical Engineering with honors from University of California, Los Angeles, where she conducted research in the CHIPS Lab.

Ahmet Oguz Sakin

Graduate Student Researcher
Electrical Engineering and Computer Sciences
Professor Alp Sipahigil (Advisor)
Ph.D. 2030 (Anticipated)

Ahmet Oguz Sakin is a Ph.D. student in Electrical Engineering and Computer Sciences (EECS) at the University of California, Berkeley, advised by Prof. Alp Sipahigil. He earned his M.Sc. in Electrical and Computer Engineering from TOBB University of Economics and Technology and a High Honors B.Sc. in Electrical Engineering from the same institution. His current research focuses on developing superconducting electro-optic microwave-to-optical transducers that coherently interface GHz-frequency quantum hardware with O-band photonic networks, using suspended thin-film...

BPNX1067: High-Efficiency Impedance Transformers for Microwave-to-Optical Quantum Transducers (New Project)

Ahmet Oguz Sakin
Nicholas Yama
Tae Gyu Ahn
2026

We are developing high-efficiency microwave impedance transformers for microwave-to-optical quantum transducers. Our goal is to match a standard 50 Ω microwave environment to a novel high-impedance electro-optic (EO) device based on a 20-kΩ impedance traveling-wave modulator. The high impedance strengthens the microwave-to-optical interaction, enhances light–matter interaction inside the EO medium, and improves the overall transduction efficiency. We will use a Klopfenstein taper design as it provides low reflection with a compact length over a broad bandwidth. We target 4–8 GHz operation...

BPNX1065: Compact, Low-Loss Capacitors for High-Coherence Merged-Element Superconducting Qubit Architectures (New Project)

Xiaoya Chen
Kerry Yu
Leo Sementilli
2026

Superconducting qubits are a leading platform for scalable quantum computing. The transmon qubit, consisting of a Josephson junction (JJ) shunted by a coplanar capacitor, is widely adopted due to its robustness against charge noise. However, its scalability is limited by the large footprint and dielectric losses at material interfaces. The merged-element transmon (MET) was introduced to enable a more compact architecture, yet in current implementations, although the JJ area can be reduced to ~3 µm², the coplanar capacitor still occupies ~100 µm². Moreover, its planar geometry generates...

BPNX1064: Annealed Al/AlOx/Al Josephson Junctions for High-Coherence Merged-Element Superconducting Qubits (New Project)

Darius F. Vera
Leo Sementilli
Kerry Yu
2026

Superconducting transmon qubits are one of the most promising platforms to realize fault-tolerant quantum computing and allow a rich parameter space of highly configurable qubit properties with various circuit elements. Ultra thin amorphous oxide tunnel barriers (such as Al/AlOx/Al) known as Josephson junctions (JJ) provide essential nonlinearity to the qubit energy landscape. Precise control over the morphology of these thin amorphous oxide tunnel barriers remains a significant challenge despite its critical role in determining structural and transport properties. Furthermore, materials...

BPNX1062: Coherent Quantum Emitter Creation via Delta Doped Silicon-On-Insulator Photonics (New Project)

Enrique Garcia
Hanbin Song
Lukasz Komza
2026

Color centers in solid-state materials are promising candidates as single-photon emitters for quantum information technologies. For color centers in silicon, ion implantation and subsequent annealing are used to create emitters in wafers at a desired density. However, ion implantation introduces damage and additional defects into the silicon lattice, potentially impacting charge environments local to color centers. In this project, we focus on the creation of silicon T centers, which are point defects composed of two carbon atoms, and one hydrogen atom. We propose to use epitaxially grown...